JHM 4:1 Center Diff Upgrade SHIMS ONLY for 01E Manual Transmission – EARLY

For Manual Transmissions Only 

NOTE: PROFESSIONAL INSTALLATING HIGHLY RECOMMENDED. WE ARE OFFERING THESE SHIMS SEPERATELY DUE TO DEMAND. THESE SHIMS DO NOT COME WITH A WARRANTY UNLESS YOU PURCHASE OUR 4:1 DIFF UPGRADE DUE TO THE INCREASED CHANCE OF INSTALLATION ERROR. 

NOTE: THESE SHIMS ARE PRECISION MACHINED AND HARDENED AND EXCEED OEM QUALITY. USING STANDARD WASHERS OR SHIMS YOU FIND ON THE INTERNET IS A SURE WAY TO DESTROY YOUR EXPENSIVE DIFFERENTIAL.

The factory torsen center differential in the S4 provide 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. Our experience has proven 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 disassemble 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 disassemble it.

01E – 6-speed EARLY OEM PN 01E409751E = B5 S4 (all), C5 A6 (all), C5 Allroad (all) – See note above regarding older 01E diffs (pre 2000) that may not be fully modifiable. 

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 
–Here is a new write up on how to perform the install on a B6/B7 A4 with the 6-speed 02x transmssion. It will help with other models since the general idea is the same. Check it out –> HERE