JC Racing

E46/E9X M3 Common Problems


Many High milage or hard used E46, E90/92/93 M3's (inc some M5/6) that are fitted with the combination limited slip unit, will be suffering a similar issue.

The early combination differentials have the short output drive flange on the right hand side, and the later slightly more robust combination diff has the short flange on the right side. These differentials start to fail in ont of two ways

1. The fist signs of a problem from the users point of view is that the car starts to make a clunking or knocking noise when turning tightly at low speed. this is caused by the output flange and the limited slip unit wearing. You can check this wear by safely jacking up and securing the rear of you car, grasp the halfshaft as the diff end, then try to push up and down on the shaft. A good diff will have about 2mm play maximum, but if you have any more then ifs starting to wear out.


2. The second sign is that you experiance the inside wheel "spinning up" and the limited slip effect has been lost. This is usually caused by too much hard driving (exactly what these cars where made for) or substantial grip or power modifications to the car



There are several remedies to cure the above issues, but you need to pick the one that is correct for your needs.. But E46 M3 owners should check its not the rear subframe mounting areas on the bodyshell not cracking out from fatigue

1. Drain your oil and replace with the updated BMW dealer oil that has a friction modifier introduced - this will help a good diff last a bit longer, but may only cure a knocking diff for a few thousand miles.

2. Fit a new output oil seal to the short shaft side of your diff - this is a salesmans trick, it will help support the short shaft for a few hundred miles and reduce the clunk. It is common to find the short shaft leaking oil due to its excessive play

3. Fit an exchange differential from BMW, it will be as good as new.... because it is new, but will likely do the same thing eventually.

4. Have an alternative LSD unit fitted, aftermarket or one from the older bmw range, these tend to use equal length shafts and are supported much better. This is by far the most common option for JCRacing customers, usally supplying there complete differential and a used E36 Evo M3 differential asking us to make a hybrid of the two. Reconditioning the unit as required. The E36 Evo M3 differential features a 2 friction plate system that many drivers prefer the feel of anyway. Some customers may opt to use the later slightly stronger combination differential unit with the short left shaft to there E46 M3.

If your car is to be used for racing or on trackdays, you may want to consider fitting the E36 Evo M3 LSD unit and whilst its apart we can increase the number of clutches and the type of clutches as well as locking effect, as well as changing the final drive ratio.

Customers that supply us with there existing differential and a E36 Evo M3 differential complete will be expecting around £600 of aditional costs to recondition and rebuild there differential - the item will look and perform better than new when you receive it back! this price is only a guide, it may vary +/- £200 depending condition.

Please note that dirty differentails and non oil drained differentials that are sent to use will suffer a slight cost penalty.

As its only the internal parts we need from the plate differential, dont be too concerned about the external casing corossion, its likly the internals are good and it is very very rare that we have to condem the lsd unit (only one in the last 5 years).






Price: £ 600.00