The factory Torsen center differential in the S4 and A4 provides a 2:1 torque distribution between front and rear wheels. 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 the most traction. Our experience has proven that this closer to even distribution is best for drag racing. If you are primarily into drag racing, this modification is not for you. However for Auto-Crossers, Road Racers, and others who prefer the twisties, JHM recommends a high-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. It will help you get a little more "oversteer" and allow you to drive the car a little more like a rear wheel drive car but still have the superior control of Audi's legendary quattro all wheel drive system.
For B6-B7 S4 and B7 A4 with the 6HP19 6-speed Tiptronic transmission only. NOTE: All B6-B7 S4s and All B7 A4s with a 6-speed Tiptronic tramission are equipped with the 6HP19 by ZF and have this center differential.
--Here is a write up on how to perform the install on a B6/B7 S4 MT. Tiptronic cars are pretty much the same except that you MUST refill all the gear oil since it is separate from the Automatic Transmission fluid that runs the transmission. It takes just under 1 quart of 75w90 synthetic gear oil that we also sell. Make sure you purchase some before the install. Check it out --> HERE
There is a core charge if we send out a JHM center differential to you (see drop box below for amount). When you exchange your center differential for a JHM unit, send your differential back to JHM and we will refund the core charge. As of 7-23-1 we currently have only a couple tiptronic cores in circulation since this is a new product and it takes time to locate them. As a result we are offering a $75 discount when sending yours in to be modified. Once we locate and stock up on cores this promotional price will end.
NOTE: If your core is damaged or worn out your core fee will not be returned or only partially returned. However if you have a damaged center differential contact us and we can discuss your options.
You may also send your differential to us for modification and not incur a core charge. We can usually modify and ship out your differential within the same day. If you will be sending yours in, select the option from the dropdown below and specify in the comments that you will be shipping it in. When shipping your differential in for modification, please include a copy of your invoice that you receive via email after you place your order. Also, put the invoice number from your order on your box when shipping it in for modification.
NOTE: It is common with this modification to notice a slight chatter when making u-turns at low speeds. This is due to the changes from the modification that make it bias differently under power and at high speeds. During normal daily driving, this chatter is not noticeable.
For shipping quotes: Please sign in or join then put the items you want in your shopping cart and proceed to checkout.
⚠️CALIFORNIA WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov