E36 medium crown wheel and pinion into e30 medium!

[JordanLee 6]

So I have a 3.15 medium e36 ratio and am wanting to put that into my e30 3.64 medium.

I understand that most of the earlier 3 series had the 188mm sizing so this means they can be interchangeable. Please correct me if I am wrong but;

Is this able to be done without too much complication?

Will be doing the bearing and seals aswell, what are some information about backlash and setting etc?

Thanks in advance am hoping this is something I can do without forking out hundreds for someone else to do.

[thorburn 121]

In short this isn't going to be easy.
This is one example. there used to be a long and more in depth thread on ohiobimmers.
http://www.bimmerforums.com/forum/showthread.php?1650106-The-E36-Diff-Thread

[Ahmedsinc 414]

A while ago I found a thread on an american site which gave a full step by step teardown and rebuild of the E30 188mm diff, right down to exploded photos and how to rebuild / shim / custom ramp angles on the LS centres. Will have a dig through the saved links folder on my old computer and see if I can find it for you. Gave all the info on preload, backlash, torque specs, etc - was really useful when I messed around with my diff.

You will need to shim the new centre to get correct backlash, if this bit is done wrong your diff will grenade itself quicksmart. Pinion preload needs to be spot on otherwise the bearing will fail pretty fast. Bear in mind that you'll need some specialty tools which aren't particularly cheap (30mm impact socket, impact gun, dial indicator, bearing puller), so if this is likely to be a one-off project it will probably be cheaper to have someone like Kayne Barrie do the job for you. You could potentially spend $500-700 just on tools alone if you can't borrow them from someone, versus a few hundred bucks to get a pro to do it for you. Not saying its an impossible branch of black magic, but you do need the right gear and a good understanding of whats happening

[JordanLee 6]

thank you for the information very much appreciate it.

now i do realise that this isnt just a sit down in a day process dont get me wrong, im aware of the consequences that come with not doing it correctly aswell.

I have possibly the opportunity to use these differnt tools off a friend if he has them at the time.

If you can find that saved link would be excellent otherwise no worries

Also who is Kayne Barrie and where is he situated? From what i can gather there isnt anybody in my area that does differentials which is a pain the ass if i have to travel and most likely leave it there as it wont be done in a day.

[Ahmedsinc 414]

Kayne is probably the resident expert in NZ on BMW drivelines. Does a lot of work for the BMW race series, amongst others. He's in Auckland, wouldn't cost much to get the diff freighted to him, chances are he can build you one from his spares pile. He's on Facefart too, look him up there - he's usually pretty quick at responding to PMs

[Ahmedsinc 414]

Ha, knew I had it saved somewhere!

http://www.bmw2002faq.com/_/technical-articles/engine-and-drivetrain/strongest-2002-limited-slip-differential-build-r74

Swapping out the centres is pretty straightforward but I'd probably defer to a pro if changing gearsets.

What options are available in E30 diffs? Can you get / import a 3.15 or similar?

[JordanLee 6]

That link is literally a bible towards this work lol. I think just reading the link above and the one you just posted, may be best to leave it up to the professionals haha! Seems like a lot of work with very minuscule room for error.

[Ahmedsinc 414]

Everything is achievable with patience, the right tools and understanding what you're doing and the necessary steps to get there. Diffs are a simple enough concept, but as you say the margin of error is minute. The reason it costs so much to have a gearset changed, or an LSD centre installed is not really the time involved but more the knowledge and skill of the builder.

And no matter which way you look at it its still cheaper to pay $500 for a gear swap than replacing a diff every few months