[yulost]

My front differential has just broke for the third time.

Why is this happening? 07 328xi 6 speed Montego blue

The first time I believe because the axle seal was bad and leaked all the diff fluid out causing it to break.

I had it rebuilt from a shop, costed me 1500$

It broke again 3 months later, they rebuilt once more

Now it just broke again.

They say it's because of my wheels (19' m3 comp wheels)which are all the same size so I highly doubt that.

What do I do, what's the cause

Thanks,

Sal

[mike5809]

What were your initial symptoms ?

[yulost]

Initial symptoms were, right before everything in the diff broke, just loud sparatic clunking and hard vibrating, and within minutes would break and lock up, same symptoms on all 3 breaks

[CoralRed335XI]

Are the rolling circumferences of your tires all the same?

[yulost]

Yes they are, all 4 wheels and tires are exactly the same size

[parabola]

How about ride height, lowered?

[deeLow]

A lot of launches?

[yulost]

Stock ride height, and 0 launches, I literally baby this thing because of these issues

[mankytron]

Bad rebuilds. Find an other shop. Your wheels are not the problem.

[Kolyan2k]

Originally Posted by mankytron

Bad rebuilds. Find an other shop. Your wheels are not the problem.

+1

[yulost]

that has to be the problem, they screwed me big time, not even the money, but all the time the car was down.

The question is now, do I find the right people to rebuild it, or grab a used one and put new seals etc. and try that?

I can get a used one for about 400$, another rebuild atleast 1500$.

[westech8383]

www.bimmershops.com
www.bimrs.org

[pits200]

I hope they didnt charge you for all the rebuilds. Go on eBuy a used diff and get it installed. If it's not that it's another issue causing this problem.

[roadkillrob]

+1 they don't know how to rebuild it - something is out of spec when they rebuild and it last for a bit and then fails - would be nice to know what is actually failing each time - guessing it is the same part as they are doing something incorrectly.

[Kolyan2k]

You have 2 options. Buy new or a used one WITH WARRANTY preferably at local junk yard or something. Do not get used with no warranty because you might get screwed yet again

[mike3000fl]

Originally Posted by yulost

that has to be the problem, they screwed me big time, not even the money, but all the time the car was down.

The question is now, do I find the right people to rebuild it, or grab a used one and put new seals etc. and try that?

I can get a used one for about 400$, another rebuild atleast 1500$.

Ok so you are thinking about spending $1500 on something that bubba and cleetus rebuilt versus $400 on something built from the factory built by Werner or Hans.

Hmmm. tough choice.

No idea how front diffs wear, but i know my rear diff has 192k miles on it and i haven't done anything to it, i would put my money with Werner or Hans. Diffs don't seem to be a wear and tear item, buy a used one and be done with it, plenty of high mileage cars with the original diffs. No reason that a used one off the shelf can't go that distance too.

[galahad05]

The more important question you need to answer is: where to take your car to get it fixed (again and for the final time). Once you find someone who really knows that they're doing, then let THEM recommend which way to go (used or rebuild).

[yulost]

Here are my rim and tire sizes, just to make sure it's not a problem.

M3 comp wheels 19's

Front tires 235/35/zr19
Rear tires 265/35/zr19

[SpeedBuggy]

Originally Posted by yulost

Here are my rim and tire sizes, just to make sure it's not a problem.

M3 comp wheels 19's

Front tires 235/35/zr19
Rear tires 265/35/zr19

I dunno, maybe someone else can chime in, but I think there is to much difference in tire rolling diameter (3.148%) between front and rear. Does not matter on rim diameter, tire diameter is the key factor. To much difference is playing havoc with the front diff.

Front tires 235/35/zr19 @ 25.48" Diameter (80.04" Circumference)
Rear tires 265/35/zr19 @ 26.30" Diameter (82.62" Circumference)
Difference of 0.827" (3.148%)

I believe you need to be less than 1%. I would change rear tires to 265/30/19 (0.857% difference in rolling diameter to front) to get back in spec while replacing/rebuilding the diff.

Front tires 235/35/zr19 @ 25.48" Diameter (80.04" Circumference)
Rear tires 265/30/zr19 @ 25.26" Diameter (79.35" Circumference)
Difference of 0.217" (0.857%)

[ny330xi]

Originally Posted by SpeedBuggy

I dunno, maybe someone else can chime in, but I think there is to much difference in tire rolling diameter (3.148%) between front and rear. Does not matter on rim diameter, tire diameter is the key factor.

Front tires 235/35/zr19 @ 25.48" Diameter (80.04" Circumference)
Rear tires 265/35/zr19 @ 26.30" Diameter (82.62" Circumference)
Difference of 0.827" (3.148%)

I believe you need to be less than 1%. I would change tires to get back in spec while replacing/rebuilding the diff.

^This

You should be running 265/30/19s out back...your difference in overall diameter is above the recommended 1%

[yulost]

Ahh I see the light at the end of the tunnel. Ordering the wrong tire setup was a costly mistake...

My plan is do 265/30/19's in the rear,

And Put in the used front diff and call it a day

I feel confident about this solution.

Thank you all for the input, this info is huge!

[DJtoad]

Originally Posted by SpeedBuggy

I dunno, maybe someone else can chime in, but I think there is to much difference in tire rolling diameter (3.148%) between front and rear. Does not matter on rim diameter, tire diameter is the key factor.

Front tires 235/35/zr19 @ 25.48" Diameter (80.04" Circumference)
Rear tires 265/35/zr19 @ 26.30" Diameter (82.62" Circumference)
Difference of 0.827" (3.148%)

I believe you need to be less than 1%. I would change tires to get back in spec while replacing/rebuilding the diff.

Absolutely correct. OP, how did we go from "all 4 wheels and tires are exactly the same size" to "Front tires 235/35/zr19 Rear tires 265/35/zr19"? That's a huge difference in both diameter and circumference and explains the diff failures. Time to stop blaming the shop for poor rebuilds. You can still run a staggered setup but will need 265/30/ZR19, not 265/35/ZR19. That should put you within the required 1% difference in diameter, even closer if your front tires are worn a bit.