Rear diff rebuild and upgrade
- Thread starter InterlagosMC
- Start date
TomK said:Splitting hairs a bit, but if they're for an m3 it's not quite bob on for the z4m as the box ratios are a little differentEd Doe said:
But it gives the idea
Oh really?! I did not know that! Anyway, now you've been summoned - give the OP the low-down on the 4.4 :lol:
lucasxdiniz
Active member
TomK
Senior member
Only 5th is the same according to wiki, but yes, as I said there is not much in it.maupineda said:
420G for the m3
1 2 3 4 5 6
4.227 2.528 1.669 1.226 1.000 0.828
S6-37 for the z4m
1 2 3 4 5 6
4.350 2.496 1.665 1.234 1.000 0.851
160mph definitely not fast enough for a road carEd Doe said:
Vanne said:
Tire size won’t matter if you’re maintaining the same overall diameter, e.g. 255/40-18 and 255/35-19 are both 26” tall.
I ran 4.10s on my old M roadster. It was an absolute blast, felt like the S54 did a line of cocaine :rofl:. For everyday [local] driving, it’s really fun and engaging. Genuinely would put a smile on my face every time I put the hammer down.
But if I’m being honest, I eventually switched back to factory 3.62. Sixth gear no longer felt like overdrive and so I found myself cruising at 3400, which is not very relaxing. For a non-trailered track car, it just made the drive that to/from that much tiring.
That said I still think it’s the best bang for buck. And so I’m going to look into something tad longer like 3.91, or even 3.85 which is very subtle but can also be had for much cheaper.
Finally managed to do some real driving on the 4.1 diff, and it's so much fun. The car feels quicker in every gear, and the extra noise and acceleration makes the car feel like it's going faster even if it's not. It's definitely a drag on the motorway though.
The issue I have had (side effect of DIYing the job perhaps) is that, once it's warmed up, the diff is making a whining noise when accelerating or going uphill. I am going to drop the oil and check for metal this week. Is there any heavier gear oil that could help with this, or do I need to admit defeat and get it looked at by a professional?
It's currently filled with Transmax 75-140 with about 50ml of redline friction modifier.
The issue I have had (side effect of DIYing the job perhaps) is that, once it's warmed up, the diff is making a whining noise when accelerating or going uphill. I am going to drop the oil and check for metal this week. Is there any heavier gear oil that could help with this, or do I need to admit defeat and get it looked at by a professional?
It's currently filled with Transmax 75-140 with about 50ml of redline friction modifier.
InterlagosMC
Member
ed80 said:
I’m getting mine rebuilt currently with a 4.1 going in and they said that the 4.1 is usually a bit more noisy as the crown wheel has sharper edge teeth than the standard ratio.
ed80 said:
I am doing the rebuild as we speak, and have found that the pinion depth needed adjusting. In my case my pattern though good apparently, is shallow, so I need to change the shim. This will also affect my backlash a bit and is very tight, on the low end of the spec at 0.06mm, so I will need to re-shim the side bearings also.
If the pinion contact patterns is not centered it will make noise. If you just reuse the same shims, though close, it won’t be 100% correct.
Many say 4.1 makes whining noises, but it could be more that they don’t adjust the pinion as is almost there with the original shims, and those are kind NLA from BMW so you need to search online or have them made.
