Starting M3 rear end/diff swap doityourself

[az3579]

Shouldn't matter. 3ers are designed with rear bias. If anything, performance should be improved?

I'm on the moon.

If that was correct, then the rear brake pads would wear quicker than the fronts, which just isn't the case.

[Hornung418]

No, Front pads wear faster because the car is moving forward and where all of the weight is under heavy braking. e46s are rear biased. Improving the rear breaks increases stability under braking.

[terraphantm]

No, Front pads wear faster because the car is moving forward and where all of the weight is under heavy braking. e46s are rear biased. Improving the rear breaks increases stability under braking.

No E46 is rear biased. In all cases, the front piston is significantly larger than the rear piston, and the front rotors are usually larger than the rear rotors. In most cases this results in a brake bias of ~2.0:1 F:R, some a little more, some a little less. The most rearward biased E46 is the CSL/ZCP with a F:R bias of 1.76:1

The rear brakes would lock up very quickly if the brakes were 1:1, let alone actually rear biased.

[Hornung418]

My mistake, I didn't mean to say that the ratio was 1:1.XX F:R. Merely that if you send some of the bias to the rear, such as the CSL, you can gain a hint of stability and decrease stopping distance because the brakes are more balanced.

I still think that if you are going to swap the rear of an M3, why not do the rear calipers?? Just don't think it makes sense to go through all the trouble to do this and not use the rotors, pads and calipers.

[mimalmo]

You can do the M3 brakes as long as you swap the trailing arms and other associated hardware back there.

Those M3 swaybars you got from your friend won't fit your non-M.

[terraphantm]

You can do the M3 brakes as long as you swap the trailing arms and other associated hardware back there.

Those M3 swaybars you got from your friend won't fit your non-M.

Fronts would fit. Rears won't without swapping all the rear hardware afaik (or maybe the subframe alone is enough, idk)

A common "OEM" upgrade iirc is the front M3 bar and xi-rear.

[mimalmo]

Like I already said, he'll need the rear trailing arms and everything else back there in order to do the rear brakes. They fit, it's just the mounting points that are different.

The rear swaybar absolutely will not fit. The front M3 sway bolts on but since you have to use the non-M rear sway, you end up with a very stiff front and a looser rear which if I recall correctly, induces understeer.

[Jlastor]

Hey guys! Thanks for the comments!

Well, Im not doing the rear brakes (although I have the trailing arms, calipers, and rotors) to keep swap as simple as possible. But also because I would have to get new pads, new rotors (the ones I have are rusted), and I dont know the condition of the e-brake. But that will come in the future, just want the diff swap for now.

For yesterday's work, I was able to get most of the things out of the way. I also inspected everything down there and was glad to see that the swap should go along well; no surprises for now.

I will be posting pictures as soon as have some real progress.

The only bad news is that I will not be able to work on the car probably until next Monday since I forgot that Im the best man for my friends wedding this weekend. So I have several activities tomorrow and the rest of the weekend. The good news is that to make up for the lost time I bought myself a set of ebay headers and a Shark Injector lol. But I will install those after the diff swap in order to really feel the difference of only the diff.

Thanks!!

[Sinister]

Can't wait the see progress pics!!! I have a full rear sub frame sitting in my garage right now. Waiting on more funding for extra parts (adjustable control arms, reinforcement kit, etc) and some rear diff service items. Good luck!

[danewilson77]

Sinister in the hizouse. Good seeing you. Good luck on the swap.

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