JHM 4:1 Center Diff Upgrade SHIMS ONLY for 01A Manual Transmission - JHM-01Ashims

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 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. 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.

To help make the proper selection below use this chart. 
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. 
01E - 6-speed LATE OEM PN 01E409751F = 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 OEM PN 0A3409751B = 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 above. If you have that diff there is no need to send it in for modification) 
02X - 6-speed OEM PN 02X409751A = 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 
--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