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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > NA Engine (non-turbo) / Drivetrain / Exhaust Modifications > HELP! 188L differential pinion preload?



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      09-25-2018, 08:03 AM   #1
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HELP! 188L differential pinion preload?

Help, I am stuck!

Does anyone know the pinion preload specs of the 188L differential?

And how do you measure the preload?



There is a website which sells a fish scale and the spec but charges like $70 for it.


Newtis.com has all the information up until the E36, nothing for the E9X at all..


Last edited by DialedIn; 09-25-2018 at 08:42 AM..
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      09-25-2018, 08:57 AM   #2
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Have you already taken it apart?

If not, it's actually pretty simple. Make a 'gouge' in the pinion/nut so you can find it's original position. Count the number of turns used to undo it (and write them down so you don't forget). Use a near crush bearing, tighten the nut back the same number of turns until your original mark is lined up. The preload should be the same as it came from the factory - you can also check it via the contact pattern of the ring & pinion.

BMW TIS used to have instructions for rebuilding diffs, but they seriously dumbed down everything in the last 20 years or so, so they took all of that out.

If you've already removed the nut and taken everything apart, personally I would give it to a shop or just buy a used diff, they're super cheap.
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      09-25-2018, 09:11 AM   #3
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Quote:
Originally Posted by hassmaschine View Post
Have you already taken it apart?
My pinion bearings were bad and noisy so I switched the old worn Koyo bearings to brand new ****.

The method you suggested would undoubtably have worked if I hadn't changed the bearings.
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      09-25-2018, 10:16 AM   #4
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you can use the contact method as well. There's a chart from the old BMW TIS floating around that shows how to set it up. type 188 differentials haven't changed a lot in the last 30 years (other than getting lamer/weaker).
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      09-25-2018, 11:15 AM   #5
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you need a dial indicator torque wrench so you can see the running torque as you're turning the pinion.

Are there any 4x4 shops around? They will have the tools to regear diffs.
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      09-25-2018, 04:39 PM   #6
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Quote:
Originally Posted by nsjames View Post
you need a dial indicator torque wrench so you can see the running torque as you're turning the pinion.

Are there any 4x4 shops around? They will have the tools to regear diffs.
I MacGyver:ed a dial indicator torque wrench from a fish scale and some maths, so that was easy.

For anyone about to attempt this job, you better be strong to be able crush that crush sleeve!! I am surprised I didn't strip the threads of the pinion rod or break my thin walled 30mm socket.
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      09-25-2018, 06:17 PM   #7
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I generally crush them with an impact.
it takes a few times to figure out how many ugga duggas is gonna get you into the right range of preload.

I hate crush sleeve pinions though, and do my best to replace them with spacers and shims at any opportunity so you can set the bearing preload precisely, while maintaining proper torque on the pinion nut.
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      09-26-2018, 07:31 AM   #8
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This is how I set it up to crush that evil crush spacer;


So my old noisy diff went from looking like this;


..to this;


Now all I have to do is mount it on the car and hope it still works!
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