Crown Gear Equipped? Opinions?

[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.

[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!

[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."