E30 gears/lsd fit in E36 diff?

[M3 Muscle]

Are the 188mm gears and LSD that come in an E30 differential interchangeable with the gears and LSD in an E36 differential?

I want to take a good set of gears and LSD from an E30 diff a put then in an E36 diff. Will it work?

[mdadgar]

Are the 188mm gears and LSD that come in an E30 differential interchangeable with the gears and LSD in an E36 differential?

I want to take a good set of gears and LSD from an E30 diff a put then in an E36 diff. Will it work?

Yes, but you need shoulder bolts (made by ARP and available at a reasonable price from PTG, believe it or not) to adapt them.

That's where 3.73 diffs come from, actually.

[ssburns]

Yes, but you need shoulder bolts (made by ARP and available at a reasonable price from PTG, believe it or not) to adapt them.

That's where 3.73 diffs come from, actually.

If properly torqued the ring shouldn't slide in relation to the diff regardless of the shoulder. If it does slide, then even with the shouldered bolts you'll eventually have some issues. I've run 2 seasons with an E36 LSD with 3.73 ring and pinion from an E30 using the original E36 smaller bolts. No issues so far.

[M3 Muscle]

Yes, but you need shoulder bolts (made by ARP and available at a reasonable price from PTG, believe it or not) to adapt them.

That's where 3.73 diffs come from, actually.

What are shoulder bolts? If I have a complete E36 diff and a complete E30 diff with I still need the shoulder bolts?

What is PTG's website? I couldn't find it.

[jahnaboi]

Hrm, could anyone explain how this conversion is done?

[m332is]

Hrm, could anyone explain how this conversion is done?

Yes... call Dan at Diffsonline and then send him a check. At least that method has worked most effectively for both my race car (e36 M3 LTW)and street car (e46 330i ZHP).

Vince

[m3ltw98]

What are shoulder bolts? If I have a complete E36 diff and a complete E30 diff with I still need the shoulder bolts?

What is PTG's website? I couldn't find it.

The shoulder bolts are only needed if the threads in the ring are 12mm and the holes in the LSD unit 14mm. Sometimes, they do not mesh depending on the model each unit comes from hence, the use of the shoulder bolt. PTG no longer races BMWs as they have gone to Panoz but Dan from diffsonline has the shoulder bolts if you still need them. Other then that, it is a lot of double checking, shimming and cursing if i had to guess. I leave it to Dan also for any differential needs.

[mdadgar]

The shoulder bolts are only needed if the threads in the ring are 12mm and the holes in the LSD unit 14mm. Sometimes, they do not mesh depending on the model each unit comes from hence, the use of the shoulder bolt.

Yeah, that's what I said. You need them to put an E30 r&p together with an E36 ltd slip.

PTG no longer races BMWs as they have gone to Panoz but Dan from diffsonline has the shoulder bolts if you still need them.

It is an ARP bolt, as I noted above. Dan is a good guy to get them from.

Other then that, it is a lot of double checking, shimming and cursing if i had to guess. I leave it to Dan also for any differential needs.

Agreed!

- Mark

[diffsonline]

I have spaces made to work with the 12mm to 14mm deal and always in stock. Not using them is asking for trouble down the road.

[JamesM3M5]

And as I've said many times before, building a BMW diff is a lot more involved than people realize. It's best left to the professionals unless you want to spend 10x more time and a lot of money getting it right on your own.

[BMWParkingOnly]

Are the 188mm gears and LSD that come in an E30 differential interchangeable with the gears and LSD in an E36 differential?

I want to take a good set of gears and LSD from an E30 diff a put then in an E36 diff. Will it work?

In short - yes. I've done this. There are two methods.
1) Take all the 'guts' from one diff housing (carrier, LS unit, gears, bearings, etc) and transplant into the other housing. The only new parts you'll need are a crush sleeve for the pinion and some new seals. You certainly can replace bearings throughout at the same time, just be prepared to spend more set-up time.
2) disassemble both diffs and mix/match the carrier and gear set. This method may require the spacers and such people have mentioned previously. It will certainly require the most set-up time, shims, etc and is necessary if you want a LS unit and don't start with a gear donor already attached to a LS carrier.

Set-up requirements may be different based on which method you use above. In my case, I kept the shims with the case they came out of and measured everything. Guess what - it was in-spec! I even re-used bearings after visual inspection. It's been a year, almost 5k street miles + ~12 track days and no issues thus far. The pinion bearing pre-load required the most care.

My donor LSD and gears were a 3.64:1 from a 735i and they transplanted into my e36 housing without drama. The same is possible from an e30 donor provided it is also a 188mm (medium case).

Based on reading your build thread, you're more than capable of the precision and patience required to perform this swap. Go for it but I still want to see the aluminum Cobra diff fitted to your LS-X powered e36!

Or, if you don't enjoy the challenge......write the check and have someone else build it for you. Somehow I don't think this fits your personality.......but James is correct, expect to spend a lot more time on it if you DIY.

Cheers,
Chet

[like2short]

The only E36 Typ 188mm that has the 14mm bolts is the one from the E36 M3.

A 3.15LSD from a 325i, actually has the 12mm ones.

If you get a E30 325i LSD, just swap the LSD and the ring and pinion over.

[jahnaboi]

So if the guts of the e30 will fit into the e36 medium case, it would theoretically work adversely correct?

I have a 3.23 lsd 97' m3 differential on hand. I currently have a 3.73 lsd e30 medium case diff in my e30. Would it be better off selling the m3 lsd and getting a e28 3.25 lsd diff or swapping the guts of the m3 diff into a e30 medium case differential?

[diffsonline]

Pretty much. And I have a good used 3.25LSD for $275 shipped too.

[BMWParkingOnly]

So if the guts of the e30 will fit into the e36 medium case, it would theoretically work adversely correct?

I have a 3.23 lsd 97' m3 differential on hand. I currently have a 3.73 lsd e30 medium case diff in my e30. Would it be better off selling the m3 lsd and getting a e28 3.25 lsd diff or swapping the guts of the m3 diff into a e30 medium case differential?

Unless you value your time at $0/hour or less and enjoy smelling like hypoid gear oil.......take Dan's used 3.25 diff and sell your 3.23 e36 diff complete. You might even come out ahead!

[sirius600]

Interesting thread, im contemplating taking my diff apart currently and grabbing out the internals from a 735 or 635 to make it a 3.46 LSD. Though im curious to the effects of decreasing the bolt size from 14mm to 12mm on the gear. Are they still sufficient enough?

Also i was browsing a thread on another site that listed some stock gear ratio's. A few posts up, someone said they took a 3.64 gear set out of a 735, whereas this list has it as a 3.46. Which should i be following?

[admranger]

Yes... call Dan at Diffsonline and then send him a check. At least that method has worked most effectively for both my race car (e36 M3 LTW)and street car (e46 330i ZHP).

Vince

This!

3.73 diff on race car from Dan at Diffsonline

[not2quick]

I've put the e30 3.73 ring and pinion into a non-M e36 a few times without trouble.

[sirius600]

Anyone have a link to instructions on how to rebuild if yourself? I dont have $800-1000 to throw at this.