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Discussion Starter · #1 ·
Hi I’m trying to install a mfactory helical diff in my 325ci I bought the mfactory shim kit but I can’t seem to get my backlash tight enough even when using all the shims the backlash is wayyy to large. Also when I use all the shims it leaves no room for the cclip anyways. iv been tryna rebuild this diff for a whole two months :( I can’t figure out what’s wrong. This is my first project car so I’m not that knowledgeable
 

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Pinion to ring
So you didn't remove the input shaft bearings or the pinion, but only replace the LSD carrier?
Adding bearing shim on the right while taking the same shim thickness off the left will reduce the ring/pinion backlash.
Adding bearing shim on the left while taking the same shim thickness off the right will reduce the ring/pinion backlash
But you also need to measure the output flange bearing preload to avoid damaging the overloaded barings.
 

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Sure you have the right carrier for the ratio you have? There are at least 2...

Likewise, last I played with the newer diffs, you get one shim each side from BMW,
and you have to change them to get different thicknesses. Does MFactory give you
a stack of standard thicknesses?
I guess where I'm headed is, if you swap the factory shims, you'll be way off.

t
would call them.
 

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Discussion Starter · #8 ·
So you didn't remove the input shaft bearings or the pinion, but only replace the LSD carrier?
Adding bearing shim on the right while taking the same shim thickness off the left will reduce the ring/pinion backlash.
Adding bearing shim on the left while taking the same shim thickness off the right will reduce the ring/pinion backlash
But you also need to measure the output flange bearing preload to avoid damaging the overloaded barings.
I changed to my output shaft bearings. I think I need more shims/clips cause the mfactory shim kit just gave me a cclip and some thin metal spacers that I’m assuming you put under the c clip
 

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Discussion Starter · #13 ·
1st pic is the ratio
2nd is left side you can also see the mfactory shims under the cclip
3rd is another cclip
4th is the right side without the cclip cause it doesn’t seat all the way
 

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Also when I use all the shims it leaves no room for the cclip anyways.
The supplied shims are for adjustment as needed, and it doesn't mean they all should be used!
Did you use the old bearings and old shims, circlips, or bought and used new parts?
Circlips must be installed or the roller bearings will fall out on the road.
Start with the old shims and see if the ring/pinion are tight or loose, then adjust the shims from here.
 

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With my helical mfactory lsd I reused the bearings and original cclips and had no issue with the backlash at all. you certain you ordered the correct lsd for your ratio? the offset of the ring gear is different for <3.07 and >3.07 ratios. Any comments from mfactory?
 

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Discussion Starter · #16 ·
The supplied shims are for adjustment as needed, and it doesn't mean they all should be used!
Did you use the old bearings and old shims, circlips, or bought and used new parts?
Circlips must be installed or the roller bearings will fall out on the road.
Start with the old shims and see if the ring/pinion are tight or loose, then adjust the shims from here.
I tried using the old cclips and that’s when the diff locked up and would rotate fully like it was as caught on something so I order the mfactory shim kit after that. I’m using new bearings from mfactory as well
 

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Discussion Starter · #17 ·
With my helical mfactory lsd I reused the bearings and shims and had no issue with the backlash at all. you certain you ordered the correct lsd for your ratio? the offset of the ring gear is different for <3.07 and >3.07 ratios. Any comments from mfactory?
No I’m not sure cause the website didn’t specify it just said it would fit a 325ci I haven’t heard from mfactory yet
 
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