Crown Gear Equipped? Opinions?

[walky_talky20]

INTRO: Hi guys. I'm more of a B5 and B6 guy, and this is my first post in the B8 Forum. I have a b̶o̶r̶d̶e̶r̶l̶i̶n̶e̶ ̶o̶b̶s̶e̶s̶s̶i̶o̶n̶ strong interest in all kinds of All Wheel Drive systems. The engineering, implementation, and pros/cons of the various systems are fascinating, in my opinion.

Several years have now passed since the debut of Audi's "Crown Gear Center Differential" (quattro VI) and I was interested in exactly where and how quickly this might have trickled down to non-RS5 models. I made a post over in B5 Land about my findings after combing through the ETKA parts catalog. I was fairly surprised at what I found. Obviously this is not a popular discussion among the B5 crowd for obvious reasons. Before I start into any of my [potentially inaccurate and probably boring] findings, I was interested to know the following from actual, real, live B8 A4 owners:

- Do you guys have a general consensus on when (or if) the Crown Gear Center Differential has been incorporated into the B8 A4 chassis?
- Do you have a consensus on which transmissions/configurations that the Crown Gear is found?
- What are your opinions on the Crown Gear vs Torsen center differential? Which is preferred and why?

Please know that I am not trying to start any kind of disagreements or ruffle any feathers. I'm just trying to get the word-on-the-street on this newer generation of quattro AWD from guys (and girls) that are way closer to the front of the line than I am. The view from these "cheap seats" could be better. ;)

TLDR: Crown Gear. Do you guys have any of these things and what are your thoughts on them?

I appreciate any and all input you guys could provide.

Kind Regards,
Walky T.

[A4Qwattro]

It’s not in any A4 for certain. Started in B8 RS5 from our generation and trickled to B8.5 DSG S4, S5.

I looked a little. Sounds like other than the reduced mass, it allows for an increased torque split of up to 15:85 FR or 70:30 FR. this is as opposed to the fixed 40:60 of the B8 A4 Torsen. So yeah I think think there are some low or changing grip conditions where the crown gear allows you to put more power to the ground over a greater amount of time. If you feel like you are on rails because of Torsen, the effect should be even more exaggerated with crown gear. Accelerating quickly is going to be even more repeatable because the crown gear is shifting even more power constantly to the axle with the most grip. I have not driven any crown gear models however.


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[walky_talky20]

Thanks for your input. I appreciate it.

To be clear: You are of the opinion that a 2013 S4 3.0T with 7-Speed "S Tronic" DSG transmission would be the earliest S4 equipped with a Crown Gear Diff?

[A4Qwattro]

Thanks for your input. I appreciate it.

To be clear: You are of the opinion that a 2013 S4 3.0T with 7-Speed "S Tronic" DSG transmission would be the earliest S4 equipped with a Crown Gear Diff?

Yes. Although I don't have blind faith in a piece a paper from Audi, everything I've seen suggest the 2013 DSG S4 has the crown gear diff.

[walky_talky20]

Oh that's great. Thanks for posting the source.

And you make a good point about taking faith in their announcements.

[Quattro420]

I own several b5 a4 and still do I also have a b8.5 a4 I am a harder driver I notice my 13 a4 can Quattro the on/off ramps harder, there is this one tight s bend that I do everyday the 13 just quattros it but I have to turn my traction control and stability control off or it won't Quattro. Audi moved the front axle location on the b8 forward compared to my b5 a4

[A4x]

I own several b5 a4 and still do I also have a b8.5 a4 I am a harder driver I notice my 13 a4 can Quattro the on/off ramps harder, there is this one tight s bend that I do everyday the 13 just quattros it but I have to turn my traction control and stability control off or it won't Quattro. Audi moved the front axle location on the b8 forward compared to my b5 a4

Your use of quattro in everyday speech and your username give you the Audizine quattro fan of the year award. Very impressive.

[walky_talky20]

Have never heard quattro used as a verb. That is great stuff. Love it.

[walky_talky20]

Ok. It seems I may have gathered the consensus. So I guess I'll get on with rest of my master plan: blowing minds.

This is what I like to call: 5 Simple Steps to why your B8 A4 may have a Crown Gear Center Differential. Well...at least some of them.

Step 1: Show me the parts.
As we have concluded above, the 2013 S4 quattro 3.0T 7-Speed "S-Tronic" DSG cars are equipped with the Crown Gear diff.
Here is the parts diagram for such a car.


Looks good. We see crown gear numbers 0B2-409-755K, which supersedes to "L".

Step 2: Is that really the first year?
Lets take a look at a 2010 S4 DSG.


^ Ok. Torsen. Nothing to see here. How about a 2011.


^Oh, snap. That looks like a Crown Gear to me. We have the stub shaft output, and the same Crown Gear part number as shown for the 2013: 0B2-409-755K, this time superseding to the same number, but with a 0B5 prefix. That makes 3 different Crown Gear part numbers so far. Are you guys pumped? I'm pumped. Is that weird? Ok, don't answer that.

Step 3: But 0B2, though. Isn't that the 6MT box?
As you may know, prefixes on Audi part numbers denote where that part debuted. So if we're seeing a 0B5 (DSG) transmission with 0B2 parts in it, that means those parts didn't debut on a 0B5 tranmission. They would come from a 6-Speed manual trans. So let's look at an S4 with a 6MT. Here's a 2009:


Torsen, yawn. Lets see a 2010. AND HERE'S WHERE IT GETS INTERESTING. I mean...if any of this interesting. At all. lol



See, in 2010 there are 2 different transmission codes for the S4 6MT. Some S4 6MT's (specifically KMR transmission code) got Torsens. Super lame, right? But some of them (the LPE trans code), got fully unannounced Crown Gear diffs. Indeed [from what I can tell] the first Crown Gears to hit our North American shores were not in RS5's at all. They were in fact S4's with 6MT's.

Step 4: Yes, LPE's actually shipped in 2010.

There are multiple listings on car-part.com and ebay for LPE transmissions pulled from 2010 model year wrecked S4's. These are tricky to screen shot, so just trust.

Step 5: Where you guys come in. A4's, eh?
There are several transmission codes for the B8 A4 2.0T 6MT. We will look at 2 common ones. Here's the KCA found commonly in the 2009's.


^Torsen. Blah. And below is the LRY, found commonly in 2011's.


^Bam. Check out that Diff part number. 0B2-409-755K. What's that? The same one in a FREAKING 2013 S4 DSG is what that is.

Crown Gear to the FACE, guys. Minds Blown!

Or not? Maybe? Maybe just a little bit? Ok. No. Just...still no.

Analysis:
It seems to me that Audi started slipping in Crown Gear diffs starting with the RS5 *and other models* in 2010. They probably didn't want to switch over cold-turkey in case there were issues with them holding up, or if there were complaints. In case of issues it would be best if it were just "some" sprinkled in and not the entire product line. Also, they have to spool up manufacturing on these things. Obviously, it would be hard for them to announce that "oh, yeah - SOME of the A4's and S4's come with Crown Gears...it's kind of random, so Good Luck!" They would just wait until production was fully switched and everything was good, THEN announce. And they'd probably prefer to hold back the announcement at least until the debut Crown Gear halo car - the RS5 - was actually available to one of their big markets.

Identification:
If you paid attention above, it seems that in all cases, the Crown Gear is equipped on cars with a stub shaft rear output, while the Torsens always get the flanged shaft rear output. So that makes identification easy. You can also just find your transmission code on your option code sticker and find out from the Parts Catalog which differential part number you have. For show-n-tell points, here is S4 6MT "KMR" vs the Crown Gear "LPE". You can see the difference in the tailshafts.





Am I crazy? Or just crazy wrong? I kindly encourage anyone to prove my silly theory wrong.

[Spawne32]

the 7 speed DSG's may have gotten some of the crown diffs towards the latter of the B8 generation (after a certain production date) but I don't know of any autos or manuals that had that crown diff in any of the B8's.

[Quattro420]

So if that is true then it looks like this 12 q5 has a crown gear I'm going to check the vin after and see but it looks like it


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[A4Qwattro]

Walky, That was a fun read! What an interesting discovery.


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[walky_talky20]

^Whoa. Somebody read my thing.

I do think it is an interesting discovery. I mean, if Audi randomly shipped half the B8 A4's with a faster processor and more RAM for the MMI, people would be all over that. Figuring out which one they had, swapping crap to get the slightly faster one, pestering dealers about it, etc. But they ship half the cars with a completely different AWD system, and nobody really notices or cares. Meh.

I am a little surprised there isn't more interest and discussion amongst the B8 A4 owners yet. It may take time. I assume in 5 or 10 years, after lots of these transmissions have been taken apart, it will be common knowledge that there are 2 completely different center diffs (and likely one of them will be more desirable). We'll see.


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[Quattro420]

When mine is out of storage I plan to look to see I think it's very interesting that some got it some didn't the q5 has it I worked on

[Jezza]

Uh, I'm super interested in this. It's freakin awesome, but I'm going to be bummed if it doesn't have a crown gear. I'm about to crawl under the car in the cold dark 20° weather to find out.

Update:

I have the LRY transmission code.



And a snub-shaft output shaft.



I just hope you're right about the crown diff. You're evidence is certainly persuasive at first glance.

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[A4 Centaur]

Great research!

[KFizz]

My transmission is coded as NGR... What does that mean?

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[Spawne32]

KXT is the trans code on mine

[A4Qwattro]

^Whoa. Somebody read my thing.

I do think it is an interesting discovery. I mean, if Audi randomly shipped half the B8 A4's with a faster processor and more RAM for the MMI, people would be all over that. Figuring out which one they had, swapping crap to get the slightly faster one, pestering dealers about it, etc. But they ship half the cars with a completely different AWD system, and nobody really notices or cares. Meh.

I am a little surprised there isn't more interest and discussion amongst the B8 A4 owners yet. It may take time. I assume in 5 or 10 years, after lots of these transmissions have been taken apart, it will be common knowledge that there are 2 completely different center diffs (and likely one of them will be more desirable). We'll see.

Based on the images in parts catalogue, any sort of Audi (A4, A5,A6,A7,A8,S models) from 2013 onwards in DSG or Manual, has a device in the center diff which resembles the one from the RS5 that Audi called the "crown gear". That little sketch even looks like the part in the video. The Auto transmissions appear to have something there that might be a crown gear which is consistent across all the auto transmission cars (longitudinal engines only). I haven't looked in transverse engine mount cars.

Then from 2010-2012, its a free-for all like you suggested above. Both kinds of diffs available.

I'm still nervous to conclude anything though.

[Jezza]

What website are you using to look up part numbers? I'm wondering if a B7 clutch and flywheel will work in a B8.

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[A4Qwattro]

What website are you using to look up part numbers? I'm wondering if a B7 clutch and flywheel will work in a B8.

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http://www.realoem.me/Audi/USA

[A4Qwattro]

Crown gear in a "lowly" A6 from 2011....

[KFizz]

So it's looking like this isn't in the 8-speed auto trans, which is disappointing.

[A4Qwattro]

So it's looking like this isn't in the 8-speed auto trans, which is disappointing.

It's not clear. There is a picture here for the 8 speed autp, for which what is inside of #7, we don't know. A theory is that Audi has taken the crown gear center diff and placed a metal sleeve over it to reduce the losses associated with slinging transmission fluid everywhere inside the casing. It's not clear if the cap has simply been omitted in the DSG and Manual transmission drawings. When you watch the videos for the RS5 (DSG) crown gear, you will see that a sleeve is thrown over the crown gear. This sleeve is not shown in the parts catalog. I think its a simple error, or rather lack of clarity, and that all 2013 and up Quattro drivetrains are using the crown gears.

[hyperunion]

It's not clear. There is a picture here for the 8 speed autp, for which what is inside of #7, we don't know. A theory is that Audi has taken the crown gear center diff and placed a metal sleeve over it to reduce the losses associated with slinging transmission fluid everywhere inside the casing. It's not clear if the cap has simply been omitted in the DSG and Manual transmission drawings. When you watch the videos for the RS5 (DSG) crown gear, you will see that a sleeve is thrown over the crown gear. This sleeve is not shown in the parts catalog. I think its a simple error, or rather lack of clarity, and that all 2013 and up Quattro drivetrains are using the crown gears.

Sounds like good news!.. all b8.5s may have the crown gear setup...

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[walky_talky20]

Thanks for the feedback guys. Sorry I kind of disappeared there, I guess I wasn't getting notifications on this thread. As a B5 guy, I don't make it into the upper echelons of AZ very often. ;)

I'm glad some of you found it interesting. Thanks to those of you who crawled under your cars to take pictures. Very cool.

My transmission is coded as NGR... What does that mean?

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NGR is the 8-Speed ZF conventional (tiptronic) automatic. I didn't really discuss those, but I believe both the 6-speed and 8-speed are using Torsens. Here's a nice cutaway of the ZF 8HP and, even though it is a stub shaft output, it is very obviously using planetary Torsen setup. It's not impossible that Audi couldn't swap in the Crown Gear, but based on a quick look at part numbers and product photos, I don't see any indications of an alternate diff.

KXT is the trans code on mine

KXT is the code a 2010-ish 6-Speed ZF Tiptronic. That one is definitely Torsen.

[hyperunion]

Thanks for the feedback guys. Sorry I kind of disappeared there, I guess I wasn't getting notifications on this thread. As a B5 guy, I don't make it into the upper echelons of AZ very often. ;)

I'm glad some of you found it interesting. Thanks to those of you who crawled under your cars to take pictures. Very cool.



NGR is the 8-Speed ZF conventional (tiptronic) automatic. I didn't really discuss those, but I believe both the 6-speed and 8-speed are using Torsens. Here's a nice cutaway of the ZF 8HP and, even though it is a stub shaft output, it is very obviously using planetary Torsen setup. It's not impossible that Audi couldn't swap in the Crown Gear, but based on a quick look at part numbers and product photos, I don't see any indications of an alternate diff.






KXT is the code a 2010-ish 6-Speed ZF Tiptronic. That one is definitely Torsen.

I always thought the zf855 was rated for higher torque. I guess not at 406lbs

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[Spawne32]

I always thought the zf855 was rated for higher torque. I guess not at 406lbs

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I know from ZF's own spec sheet the 6HP28 is rated for 700nm which is 516ft lbs roughly, and thats according to audi's sheets as well.

[A4x]

Is it possible for a 2011 8 speed to have a crown gear center diff?

What's the best way to check, crawl under and look or check the trans code?

[Black Raptor]

My b8.5 manual 6 speed is crown gear. When I drive my b8 and b8.5 back to back on twisty roads. The b8.5 is a little more playful and the back end will step out. I would say this could be because of tires. But I run the same tires I use for auto cross on both cars.


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[mtroxel]

^Whoa. Somebody read my thing.

Walky I always read your posts. When my $950 alternator crapped out on one of my B5's, your post help me fix it for $0.85!!! No lie. That was the cost of the brushes I bought at NAPA.

[SixtyFortyDiff]

Well then, I just stumbled across this today, (and also your "Crown Gear Musings" post from December of 2017) and you can consider my interest VERY piqued!!

Walky, you are I are apparently cut from the same cloth (notice my username...). Ever since getting into the VW/Audi scene, and watching some rally/rallycross videos online, I too have been "borderline obsessed" with the nitty gritty details of how various AWD systems work, their designs, and pros/cons of each, regardless of manufacturer. The amount of times you'd find the words/phrases such as "differential" / "asymmetrical torque split" / "active diff" in my search history would likely be mildly disturbing to most.

I drive a 2010 B8 S4 with manual transmission. Note: it has a sport differential (this matters, I think - I'll get to that in a minute). I always assumed I had the Torsen T3 as my center diff, because I thought all manual B8s had the KMR trans, and that the Crown Gear was only in 2013 B8.5 DSG cars. However, upon reading through this post and immediately running full speed to the garage, I discovered that my trans code is "MKY LPE" which based on your research in ETKA, means I *should* have the Crown Gear.

So I crawl under the car to verify using the flange vs. stub-shaft theory, to find a somewhat odd discovery. Mine definitely does NOT have a flanged connection to the rear drive shaft. It DOES have a stub-shaft output, which supports the Crown Gear idea, however, the piece between the shaft and the trans isn't typical of the drawings and pictures in this post. Instead of the silver disc/puck, mine has what looks to be a black plastic piece bolted directly to the trans casing (i.e. - it doesn't rotate). The best way I can describe it is to picture what the asterisk symbol ( * ) looks like, and imagine that six-pointed shape extruded in black plastic approx. 1-2" thick, with the output shaft running through the center. This might be irrelevant, but it's different, so it feels worth mentioning.

Side note: I would post the picture I took, but apparently I can't upload pictures directly to this site?! (Pretty sure this is my only post on AZ, forgive me for being a noob). If anybody has somewhere to host pictures, I can send you the pic to host for me!

Based on my findings, I suppose it looks like I may have the Crown Gear, which... I'm actually not sure is a good or bad thing. I understand the principle by which the Torsen T3 "locks" (biases torque is probably the more appropriate term) as input torque is applied - it's a function of the helix angle of the planet gears. Got it. Makes total sense to me.

BUT, how the Crown Gear "locks" is still somewhat fuzzy to me. I get how the crown gear diameters where they interface with the face gears gives a rear:front nominal torque split of 60/40 (same ratio as the Torsen T3), but the clutch pack actuation is the part I don't fully understand. I actually reached out to Audi multiple times on this for clarification but was unable to get in contact with any technical folks who really understood my question. What I don't get is how an axial force is developed within the diff such that the clutch packs are compressed. From my limited understanding of interaction between spider gear to side gear, ("face gear to crown gear" in this case) I can somewhat understand an axial force being applied when there is a difference in speed - i.e. - when the face gears rotate to allow speed differentiation between the front and rear axles. But if that's the only way lockup force is applied to the clutch plates, then that means you need axle speed difference to occur before the diff can start to limit slip/transfer torque/lock up. Which, seems inferior to how the T3 works, which begins to "lock" as a function of input torque, rather than a shaft speed differential. Any insight would be appreciated!

I made a comment earlier about my car having a sport differential. The RS5 comes standard with the sport diff and the crown gear, which leads me to believe there may be some correlation between the sport diff and the crown gear on models where the sport diff is optional, like the S4. Maybe the sport diff functions more desirably with the crown gear as opposed to with the Torsen T3? But then again, I believe the RS7 has a T3, and it also comes standard with the sport diff, so that would add an exception to my theory. Walky, maybe you could do some digging in ETKA on the RS7 trans (ZF 8 speed) and the sport diff? This might help us find out if there is a correlation between the two!

[Phrost2.0]

I just want to know what my 2011 S4 6MT has so I can convert it to RWD and drift the s*** out of it

[walky_talky20]

Well then, I just stumbled across this today, (and also your "Crown Gear Musings" post from December of 2017) and you can consider my interest VERY piqued!!

Walky, you are I are apparently cut from the same cloth (notice my username...). Ever since getting into the VW/Audi scene, and watching some rally/rallycross videos online, I too have been "borderline obsessed" with the nitty gritty details of how various AWD systems work, their designs, and pros/cons of each, regardless of manufacturer. The amount of times you'd find the words/phrases such as "differential" / "asymmetrical torque split" / "active diff" in my search history would likely be mildly disturbing to most.

I drive a 2010 B8 S4 with manual transmission. Note: it has a sport differential (this matters, I think - I'll get to that in a minute). I always assumed I had the Torsen T3 as my center diff, because I thought all manual B8s had the KMR trans, and that the Crown Gear was only in 2013 B8.5 DSG cars. However, upon reading through this post and immediately running full speed to the garage, I discovered that my trans code is "MKY LPE" which based on your research in ETKA, means I *should* have the Crown Gear.

So I crawl under the car to verify using the flange vs. stub-shaft theory, to find a somewhat odd discovery. Mine definitely does NOT have a flanged connection to the rear drive shaft. It DOES have a stub-shaft output, which supports the Crown Gear idea, however, the piece between the shaft and the trans isn't typical of the drawings and pictures in this post. Instead of the silver disc/puck, mine has what looks to be a black plastic piece bolted directly to the trans casing (i.e. - it doesn't rotate). The best way I can describe it is to picture what the asterisk symbol ( * ) looks like, and imagine that six-pointed shape extruded in black plastic approx. 1-2" thick, with the output shaft running through the center. This might be irrelevant, but it's different, so it feels worth mentioning.

Side note: I would post the picture I took, but apparently I can't upload pictures directly to this site?! (Pretty sure this is my only post on AZ, forgive me for being a noob). If anybody has somewhere to host pictures, I can send you the pic to host for me!

Based on my findings, I suppose it looks like I may have the Crown Gear, which... I'm actually not sure is a good or bad thing. I understand the principle by which the Torsen T3 "locks" (biases torque is probably the more appropriate term) as input torque is applied - it's a function of the helix angle of the planet gears. Got it. Makes total sense to me.

BUT, how the Crown Gear "locks" is still somewhat fuzzy to me. I get how the crown gear diameters where they interface with the face gears gives a rear:front nominal torque split of 60/40 (same ratio as the Torsen T3), but the clutch pack actuation is the part I don't fully understand. I actually reached out to Audi multiple times on this for clarification but was unable to get in contact with any technical folks who really understood my question. What I don't get is how an axial force is developed within the diff such that the clutch packs are compressed. From my limited understanding of interaction between spider gear to side gear, ("face gear to crown gear" in this case) I can somewhat understand an axial force being applied when there is a difference in speed - i.e. - when the face gears rotate to allow speed differentiation between the front and rear axles. But if that's the only way lockup force is applied to the clutch plates, then that means you need axle speed difference to occur before the diff can start to limit slip/transfer torque/lock up. Which, seems inferior to how the T3 works, which begins to "lock" as a function of input torque, rather than a shaft speed differential. Any insight would be appreciated!

I made a comment earlier about my car having a sport differential. The RS5 comes standard with the sport diff and the crown gear, which leads me to believe there may be some correlation between the sport diff and the crown gear on models where the sport diff is optional, like the S4. Maybe the sport diff functions more desirably with the crown gear as opposed to with the Torsen T3? But then again, I believe the RS7 has a T3, and it also comes standard with the sport diff, so that would add an exception to my theory. Walky, maybe you could do some digging in ETKA on the RS7 trans (ZF 8 speed) and the sport diff? This might help us find out if there is a correlation between the two!

Hey man, I had forgotten about this thread and just saw your reply. I'm glad I'm not the only guy who is AWD crazy. As evidence of my craziness (other than this thread? lol), here is a picture of the side of my Volvo V50 T5 AWD 6MT, which I felt deserved - no *required* - these ridiculously large 80's-Tastic "INSTANT TRACTION" stickers. I designed them myself and had a friend cut them for me.



I very much enjoy watching people pause to read over the entire sticker in parking lots and such. "Look Honey, it has All Wheel Drive!" they say. My dream is to at some point have an Audi with a huge "quattro" script across the doors. Something ridiculous like "QUATTRO" and "GEN IV - with TORSEN T1 by Gleason Power Systems".

I too have watched Audi's "Crown Gear" explainer video many times. I'm pretty sure that the clutch packs are wound up pretty tight by default and lock a bit tighter when they heat up. I'd love to have one in my hands to play with.

For photos, upload to Imgur and then use the direct link.

As far as Sport Diff correlation to Crown Gear - I think their plan is to go all Crown Gear where possible, so I don't think they spec them one way or the other based on performance. I assume the Sport Diff does add weight, so they may like to pair it with the lighter crown gear setup to offset that a bit. However, I'll bet more likely the production of KMR or LPE was just based on shipments of the transmissions from suppliers/assemblers and they just desired to have a certain number of each per model year as they phased in Crown Gear secretly under our noses.

[SixtyFortyDiff]

Hey man, I had forgotten about this thread and just saw your reply. I'm glad I'm not the only guy who is AWD crazy. As evidence of my craziness (other than this thread? lol), here is a picture of the side of my Volvo V50 T5 AWD 6MT, which I felt deserved - no *required* - these ridiculously large 80's-Tastic "INSTANT TRACTION" stickers. I designed them myself and had a friend cut them for me.



I very much enjoy watching people pause to read over the entire sticker in parking lots and such. "Look Honey, it has All Wheel Drive!" they say. My dream is to at some point have an Audi with a huge "quattro" script across the doors. Something ridiculous like "QUATTRO" and "GEN IV - with TORSEN T1 by Gleason Power Systems".

I too have watched Audi's "Crown Gear" explainer video many times. I'm pretty sure that the clutch packs are wound up pretty tight by default and lock a bit tighter when they heat up. I'd love to have one in my hands to play with.

For photos, upload to Imgur and then use the direct link.

As far as Sport Diff correlation to Crown Gear - I think their plan is to go all Crown Gear where possible, so I don't think they spec them one way or the other based on performance. I assume the Sport Diff does add weight, so they may like to pair it with the lighter crown gear setup to offset that a bit. However, I'll bet more likely the production of KMR or LPE was just based on shipments of the transmissions from suppliers/assemblers and they just desired to have a certain number of each per model year as they phased in Crown Gear secretly under our noses.

Oh cool, you're alive!

That is a very 80's-Tastic sticker - pretty cool that you designed it. I think you definitely need the Torsen T1 sticker on your Audi, that'd be awesome, paying some homage to the rally history of quattro.

So after posting my last post months ago, I saw your quote on your other Crown Gear Musings post:

"This begs the question: Is the Crown Gear more desireable, or less? Newer does not always mean better. It seems to me that Audi was probably not having a major loss in sales due to people think their Quattro system was lousy. It was pretty amazing as is. I think the major push was to design something in-house to avoid the pesky royalty fees associated with Torsen. So this is all a cost-cutting move. They are totes cost-cutting on our precious AWD, guys.

Pros/Cons: It seems to me that Crown Gear might lose some of the magical "pre-emptive torque transfer" abilities that Torsen has. Even the marketing video says it "springs into action". You lose traction, then - based on front/rear axle RPM differences (THAT MEANS WHEEL SPIN) - it progressively locks and transfers torque. That's quite different than a Torsen. Secondly, it's locking method uses what Audi is calling "plate packs" to create a "locking torque". Yeah, those are clutches. And themz prolly gonna wear out. Again, Torsens don't have clutches and they virtually don't wear out. On the plus side, it does provide for torque transfer even with zero traction on one axle - something Torsen can't do. How well it works (and for how many miles) is probably not yet widely known. But there are several different part numbers, so I'd say they were at least initially making some tweaks."

I geeked out pretty hard and did some reading on the various internal forces in differential gears, as well as did some scouring of Google's records of patents and found some cool stuff regarding the crown gear design (mostly patent applications by VW/Audi in the 2006+ timeframe, but also some applications by others) and now I think I understand how it works. So whether I actually have it in mine or not ( jury is still out - I guess I'll never know, which is OK) I'm at least mentally appeased in understanding it's operation.

From Google patent US5472385A, discussing the clutch packs ("thrust washers") in a crown gear differential: (1) "the thrust washers provide reaction surfaces for the expected gear reaction forces generated between the teeth of the side gears and the teeth of the pinion gears during torque transfer." (2) "the thrust washers... may be constructed of a friction material so that the gear reaction forces generated during differentiation causes torque to be directly transferred to the carrier..."

From Google patent EP1906053B1, discussing the clutch packs ("disc brakes") in a crown gear differential: "the disc brakes are closed respectively by the axial components of the effective gearing forces and thus inhibited a compensating movement between the two output gears. Since the meshing forces increase proportionally to the transmitted drive torque, also the locking action of the differential gear increases in proportion to the transmitted drive torque."

So all that to say, apparently the physics of gears and the geometry of the tooth shape generates axial forces whenever a gear transmits torque, and this force is what provides the force to partially lock the clutch pack. Pretty cool stuff! I had no idea these forces existed in such an application - I studied electrical engineering in college and took some mechanical engineering courses as well, but this was news to me (I wish I'd had a chance to take more mechanical courses, but Google does a pretty good job too lol).

I can share more if you're interested (or just Google "gear forces"/"line of action"/"pressure angle" for a plethora of sources on what determines the magnitude of these forces), but to me it looks like the Crown Gear seems to be a suitable replacement for the Torsen T3 since it can apparently transfer locking torque prior to differentiation (aka - before wheel slip occurs, much like the Torsen) due to these "axial components of the effective gearing forces" that are "proportional to the transmitted drive torque."

[walky_talky20]

Just found my way back here (I should probably figure out how subscribing to threads works, after being a member for 10 years, eh? lol).

That's an interesting point about the axial forces and I can see how that would effectively provide a locking effect before wheel slip. Basically the gears are cut so they try to "walk" away from each other a bit, and this ends up putting pressure between the output gears and the housing. Thus locking the axles together progressively. (Time to watch the Crown Gear video *again* with this in mind). The only problem is that is it's using friction within the "plate packs" to transfer the torque. And the plates will necessarily be slipping when torque is transmitted and any amount of RPM difference exists between the front and rear axles. Like putting your foot down when turning...which happens a lot.

I suppose it is probably designed to just walk a little further as the plates get thinner - so wear does not immediately affect the locking ability. And the material is probably fairly awesome so it doesn't wear too fast. But it should be noted that friction material is necessarily going to end up in the gear oil. And that stuff should probably be changed more often as a result. I'm sure Audi still says the gear lube is lifetime.

This does beg the question if some aftermarket outfit will take one of these things apart and swap the "plate packs" to something with more aggressive friction properties. Like they did with the Torsen washers. Crown Gear Plate Pack Upgrades, we might call them. +40% torque transfer capability! +20% over OEM RS5 Crown Gear! I guess time will tell.

[gnxuser]

wow and interesting read. mine is a MRR transmission code, does it mean it definitely has the Crown Gear?

[RattRandee]

Hella subscribed, this is the best read on here! Crawling under my car tomorrow after work


Sent from my iPhone using Audizine

[Kolbenringe]

Hey, first I wanted to send out huge props to walky and other contributors here. The type of analytical discussion we have here is reminiscent of the old Quattro List/Audifans group, which was likely the first such group for Audi owners online in the infancy of the internet. The discussions were via email distribution and highly analytical and technical, with numerous engineers and hands on people. Some even started their own Audi parts businesses from the knowledge and connections they gained from there. Even if we don't end up with a consensus or we are wrong, the analytical nature of the talks and walky's input has opened up an insightful dialog that is informative and even entertaining. It was because of the Q-List that I began wrenching on my own cars and rebuilding and restoring them.

So for my example: German 2011 A4 Avant, 2.0 tfsi S-tronic Quattro, MSA transmission code. I have the outdrive associated with the crown gear. I also hunted around online for used transmissions and they all have the same output shaft. I can't imagine that I have one, but my particular car has lots of mystery combinations on it that even the Audi dealer is having trouble with (even little things like my oil pan drain bolt). The 1LJ brakes I might have an explanation for, though ;) This is also one of the early transmissions that had defective drive range sensors, which were replaced under warranty.

I actually doubt I would feel any difference, though the 40/60 split of the standard center differential is noticeable on the uncontrolled sections of the German highways when rounding turns.

Here's what it looks like on our equivalent of Craigslist (which is operated by Ebay): https://www.ebay-kleinanzeigen.de/s-...18073-223-4408

and another: https://www.ebay.de/itm/Audi-Getrieb...-/272911356881

[Kolbenringe]

Here is a video that some of you may or may not know. The CG shows the relationship of the Crown Gear Differential with that output shaft.