JHM Group Buy: 4:1 Center Diff Upgrade(01E, 0A3, 02X, 01A)(Manual Trans only)

[Dan@JHM]

This is a nice season change group buy we are offering for our 4:1 center differential upgrade. This upgrade will be available for the following models:


- 01E 6 Speed Trans = B5 S4, C5 A6, Allroad (Please read note on 99 and earlier model(t-1) type 01E diffs)

- 0A3 6 Speed Trans = B6 S4

- 02X 6 Speed Trans = B6/B7 A4

- 01A 5 Speed Trans = B5/B6 A4 (Please read note on 99 and earlier models)

* For manual Trans only


NOTE: Due to the core exchange element of this product, this will be a send in your own diff to modify purchase only. We simply do not have enough cores on the shelf to support a group buy. However, once we have received your center diff, we will be able to modify and send it out same day if the package arrives to us in time. If not then it will be sent out the very next business day at the latest.


Retail pricing on JHM Center Diff: $350 plus shipping


Group Buy pricing:

- 5(+) units sold = $25 off

- 10(+) units sold = $50 off

- 15(+) units sold = $75 off

- 20(+) units sold = $100 off


Group Buy Members:

1. theredcaron
2. Tarmac(01E)(PAID)
3. dylanbike1
4. sholitz(01A)
5. jettin123
6. RallyeG(01E)
7. downhillracer
8. HotSauce
9. racing_fan(OA3)(PAID)(local install)
10. alwaysaudi(0A3)(PAID)
11. Satummoo(01A)
12. pafable(02X)(PAID)
13. doctorheine
14. lunamarA4(02X)(PAID)
15. AudiOso(0A3)(PAID)
16. downhillracer(01A)
17. fernank1987(02X)
18. turbonick(0A3)
19. Max(01E)
20. 034 Customer(01E)(PAID)(local install)
21. tbomb80(02X)(PAID)
22. 617 Bones(01A)(PAID)
23. WRC_4kqt(01E)(PAID)
24. D.K(0A3)
25. noznab(0A3)
26. twiztids4(01E)(PAID)
27. lunamarA4(02X)(PAID)
28. AUDIocee(0A3)(PAID)
29. mikekehler(PAID)
30.


...



More information about the JHM 4:1 Center diff upgrade:


Web page: http://www.jhmotorsports.com/shop/ca...0fea030989309c




The factory torsen center differential in the S4 and A4 provides a 2:1 torque distribution between front and rear. What does this mean? This enables the end of the car that still has traction (most of the time the rear) to deliver double the torque to the tires with traction. JHM's experience has found that this closer to even distribution is best for drag racing. So this modification is not for you if you are into drag racing primarily. However for Auto Crossers, Road racers and others who prefer the twisties JHM recommends a bias ratio of 4:1. This is the same bias ratio that Audi has provided in the stock RS4 driveline.


So if you are tired of going through corners while using a lot of throttle and still getting "understeer" then this product is for you and will help you get a little more "oversteer" and allow you to drive the car a little more like a RWD car but still have the superior control of AWD.


NOTE: For 6-speed (01E) transmissions: We can only perform the FULL modification on the T2 style differentials originally equipped in 2000 and newer B5 S4s, C5 A6s, C5 Allroads and B6 A4 (3.0L only, 02-early 03). These T2 diffs have one of the following PNs on the outer case; 01E 409 751 E or 01E 409 751 F. Some of the pre 2000 diffs may be T2 diffs and have these part numbers as well. For those the full modification could be performed. If your diff is older and does not have one of these part numbers or has NO part number at all then it is most likely a T1 style diff. If you have a T1 we can only modify half of the diff due to its older design so you will not get a full 4:1 diff, it will be somewhere in between a 2:1 and 4:1. We won't know 100% for sure until we dissasemble the diff if your diff does not have one of the part numbers listed above. Some of the older diffs have been replaced over the years from other cars or due to wear so there is no other way to tell until we receive your diff and dissasemble it.


NOTE: For 5-speed (01A) transmissions: We DO NOT offer a core exchange due to a high failure rate on these diffs. We will only modify yours that you send in. Also there are 2 different diffs in the 5-speed 01A transmission, we only do the late 99.5 and up. Use this PICTURE to confirm you have the right diff to send in. CLICK HERE. These diffs are interchangeable, so if you have the older diff you can buy a newer diff from a wrecking yard to have modifed by us, then you can replace your older 2 piece unit with the modified late JHM unit.





To help make the proper selection below use this chart.
01E - 6-speed = B5 S4 (all), C5 A6 (all), C5 Allroad (all), B6 A4 6-speed (02-03 3.0l V6 only all other 6-speed A4s have the 02X) - See note above regarding older 01E diffs (pre 2000) that may not be fully modifiable.
0A3 - 6-speed = B6 S4 (all) and some 05.5 B7 S4s (note: we have seen some 05.5s with the T3 diff which is already a 4:1 and does look different than the one in the picture below. If you have that diff there is no need to send it in for modification) 02X - 6-speed = B6 A4 (04 and up) and B7 A4 (all). 01A - 5-speed = B5 A4 (99.5 and up) and B6 A4 02-04 with 5speed transmissions . NOTE: We do not modify the older A4 diffs, see picture below for more info. Also we only modify your diff and do not supply cores on these diffs due to the higher failure rate on these units.

INSTRUCTIONS: Here is a write up on how to perform the install on a B6/B7 S4. It will help with other models since the general idea is the same. Check it out **> HERE


NOTE: It is common with this mod to notice a slight chatter when making u-turns at low speeds. This is due to the modification to make it bias differently under power and at high speeds. Normal daily driving it is not noticeable.



Please email or reply to this thread if you are interested in joining this GB.


Due to our high call volume, Please email [email protected] with any questions about this GB.

[theredcaron]

I would love to have this on my car for the twisties!!
I am just worried about getting around in the snow with more rear bias. Does anybody have experience with the 4:1 diff in extended time in the snow?

[Tarmac]

I’ve always wanted to add this mod on my b5 s4 shopping list.

What about international orders, more than likely, to be expected it’s not going to be feasible for me to send my Center diff over seas. Shipping would make this a very expensive exercise, unless you have another option/alternative,,,, I’m hopeful!!! ;-)

[Tarmac]

I would love to have this on my car for the twisties!!
I am just worried about getting around in the snow with more rear bias. Does anybody have experience with the 4:1 diff in extended time in the snow?

Not in Australia LOL :-)

[Scotty@Advanced]

For those overseas, I have a few dozen 01E center Diffs I can sell used, and send to JHM for modification. I can't spare the other differentials unfortunately.

[sy0296]

also interested in performance in snow since this car will see lots of it every snowboarding season

[Johann2.7t]

will this effect gearing in anyway? Ive always disliked the high rpms in 6th gear on the highway.

[whartung]

will this effect gearing in anyway? Ive always disliked the high rpms in 6th gear on the highway.

no

[awd2ks4]

4:1 diff FTW

[julex]

will this effect gearing in anyway? Ive always disliked the high rpms in 6th gear on the highway.

For that you need to re-build transmission with custom sized gears.

[Tarmac]

I will be the first & let someone be the last 20. I'm in

2001 B5 S4 01E 6 Speed Trans

[Tugboatguy]

I would love to have this on my car for the twisties!!
I am just worried about getting around in the snow with more rear bias. Does anybody have experience with the 4:1 diff in extended time in the snow?

I've got an 07 S4 which comes stock with the 4:1, I put my snow tires on and blast up the local mountains in the winter no problem

[arotished]

So B5 RS4 already have 4:1?

[theredcaron]

I've got an 07 S4 which comes stock with the 4:1, I put my snow tires on and blast up the local mountains in the winter no problem

awesome!
thanks for the insight

[dylanbike1]

I'm in.

However- what is the cutoff date for the GB. I don't want to wait a 2 months to place my order.

[sholitz]

I'm in. I've been waiting for a deal on one of these...

[jettin123]

I am in depending upon when the group buy will be cut off and the orders will be shipped.

[RallyeG]

I'm in: 01E

[walky_talky20]

I am just worried about getting around in the snow with more rear bias.

This mod doesn't just add more rear bias. It adds a more aggressive "torque bias ratio" or TBR. Basically it is allowing the center diff to transfer more of the torque front/rear as needed. The factory 2:1 diff gives anywhere from 33/66 to 66/33 front/rear split. This 4:1 upgrade would allow up to a 20/80 OR 80/20 front/rear split. This should make it able to provide even more superior traction ability in the snow as it allows an even greater traction "offset" between the axles before wheel slip occurs.

[downhillracer]

very interested in this! I may be in depending on how long and how many people we can get!! Will be following this thread closely! Thanks JHM

[Jeff]

Dan,

Do you guys carry any type of warranty on the diffs? I recall a while back that a few people bought the "upgrade shims" from a seller online to modify their own diff, and a few of them blew their diffs after a few months. Now this cannot necessarily be directly related to the mod itself--for it could possibly be caused by install error and other factors such as abuse...but knowing there's some kind of warranty will make the prospective buyers more at ease to purchase (including myself).

[HotSauce]

Dan,

Do you guys carry any type of warranty on the diffs? I recall a while back that a few people bought the "upgrade shims" from a seller online to modify their own diff, and a few of them blew their diffs after a few months. Now this cannot necessarily be directly related to the mod itself--for it could possibly be caused by install error and other factors such as abuse...but knowing there's some kind of warranty will make the prospective buyers more at ease to purchase (including myself).

In based on this answer.

[racing_fan]

I am in.

OA3 6 Speed Trans

[JimmyBones]

I would buy in but I would need to mail my core in after doing it because I can't be without my car.

[alwaysaudi]

I'm in 0A3 6 Speed Trans

[Satummoo]

I'm in, 01A 5-speed b6 :-)

[BerNur]

I would buy in but I would need to mail my core in after doing it because I can't be without my car.

x2

[jaybquick@JHM]

Thanks again everyone for your interest. We will be updating lists and getting back to you guys with more details. We are trying to catch up a little bit today while everyone else is off, but Dan will chime in shortly.

[jayiszraw]

This mod doesn't just add more rear bias. It adds a more aggressive "torque bias ratio" or TBR. Basically it is allowing the center diff to transfer more of the torque front/rear as needed. The factory 2:1 diff gives anywhere from 33/66 to 66/33 front/rear split. This 4:1 upgrade would allow up to a 20/80 OR 80/20 front/rear split. This should make it able to provide even more superior traction ability in the snow as it allows an even greater traction "offset" between the axles before wheel slip occurs.

curious, if thats the case why is it said that the stock differential is best for drag racing?

[mnooooa4]

Interested based on warranty answer and when the cutoff is.

[RolledMySTi]

Good deal. I love my JHM 4:1 diff. I'm driven on a snow packed road with disabled traction control and summer tires with no issue with this diff. Very fun in the snow too! Over a year and a half with no issues.

[Tarmac]

The GB list is not updating, anyone know what's going on is this GB on or off?

[BlkdoutS4]

The GB list is not updating, anyone know what's going on is this GB on or off?

Jay just posted in here yesterday saying that they would be updating the list shortly...

[doctorheine]

im in for spot 20.... how do i find out how much shipping is ???and warranty???

[lunamarA4]

might be in depending on how hard it is to remove and reinstall 02X 6 Speed Trans = B6 A4

[Tarmac]

might be in depending on how hard it is to remove and reinstall 02X 6 Speed Trans = B6 A4

I’ve sent an email through but no reply just waiting. JHM you need to wake this post up & start adding names/numbers. This is a good mod, hopeful more will join in the GB.

[Dan@JHM]

Hey guys sorry about the delay, I just updated the GB list. Please check the list and let me know if you need to be added or taken off. Also for those of you that did not specify what year/model car you have or the transmission type please let me know so that way we will know what to expect.


Warranty:

We will cover any issue with our parts for the upgrade and/or workmanship but cannot cover a customer's center diff itself. If you send a center diff into us that is worn or damaged beyond repair we will not modify the diff in the first place. That being said we have only seen a couple of diffs that have been bad enough for us not to modify.


Time frame:

I will let this go for 2 weeks or we hit 20, whichever comes first. At that point we will modify the price onto the website to reflect final gb pricing and you will be able to place your order and send your diff into us. I will give you further instructions when we reach that point though. If we do hit 20 I will leave the group buy open for a couple weeks beyond that to let all of the late comers join in with their orders.

[Tarmac]

Thanks for the update. Numbers are looking good, cheers ;-)

[617 Bones]

Subscribed! I'm interested... but want to know what shipping will look like to the East Coast (02142).

[downhillracer]

I will be in for an 01A if we hit 20 !