Mixing diffs

[Guest Denny Crane]

Can a Ti diff be used in an E30 - Assuming yes due to the same design of the rear suspension?

Anyone have access to the bits/ tools to make an open diff an LS unit? Darren?

the diff in question http://www.trademe.co.nz/Browse/Listing.aspx?id=96826223

Ediit - Would be important to acertain whether thats med / small case?

I've been on the hunt for a med case 3.25 E30 LS unit, but they came in Sport Evo's and 324td's only - so good luck to me, this diff seems to be about as close as i'm going to get for resonable money.

Also, mildly related... I know increasing the lockup of a diff induces understeer, how would increasing the lockup of a bmw LSD from 25% to 40% affect handling? I know all the OG alpina cars (E30 / E28 etc) all used 40% lockup slippers.

Edited April 21, 2007 by Denny Crane

[will 169]

Looks like a small case diff to me so probably not much use to you if it is the same case as used in the e30, you will end up with the same problems Chris is having at the moment with driveshaft alignment.

You would probably need to source a subframe that accomodates the small case diff and disc brake trailing arms to keep the alignment correct.

My thoughts anyway for what they are worth.

Will

[Guest Denny Crane]

Worth more than the proverbial 0.02c, Will!

Going to a smaller diff isn't an option. Looks like I will pass on this particular unit.

[westy 614]

What about a m3(3ltr) internals?

I believe these are 3.23?? and are a medium case (type 188) diff so the internals should be interchangeable.

Otherwise an early e36 325 manual I think is around 3.2?.

The crown and pinion may be usable.Bolt the LSD unit to the crown wheel.

A lot of ???????? I know but somewhere to start.

[Mike 1]

Looks like a small case diff to me so probably not much use to you if it is the same case as used in the e30, you will end up with the same problems Chris is having at the moment with driveshaft alignment.

You would probably need to source a subframe that accomodates the small case diff and disc brake trailing arms to keep the alignment correct.

My thoughts anyway for what they are worth.

Will

Will, can you explain further on these alignment problems? Small and med case diffs for e30's are directly interchangeable.

Sorry for hijack sam -agreed with will on that being small case, just compared it to my spare

Edited April 23, 2007 by Mike

[will 169]

Will, can you explain further on these alignment problems? Small and med case diffs for e30's are directly interchangeable.

Sorry for hijack sam -agreed with will on that being small case, just compared it to my spare

Simple check... measure from the rearmost mounting bolt hole to the centre of the output flanges on both diffs, the measurement of the medium case is bigger by about 20???mm (can't remember exactly what the measurement was ), so, if you are using a small case subframe and put a medium case into it, the alignment of the sideshafts will be worse by that amount horizontally.

Check the pic below from Chris, it will explain what I am trying to say. He is using a small case in a medium case subframe, check the horizontal angle of the sideshaft.

[Mike 1]

Ah thanks, I've got a med case diff in a small case frame, guess I'll have to check and see how the angles are.

What part is different between the subframes then? Trailing arms and subframe all have same part no between models.

Edited April 23, 2007 by Mike

[ED1RTY 2]

Difference is the disc/drum t/a's

The disc'd t/a's are offset for a 8 bolt diff and the drum brake ones are offset for a 6 bolt.

Its wierd but when its all together on the ground in front of you it makes a big difference, now that i have the 8 bolt diff in its all good. No angle. Only now that it is in the car and there is camber.

[Mike 1]

But my car had discs with a small case diff? Was completly stock when I got it so I doubt someone has been changing stuff on it.

Is it going to matter that much? I guess maybe a bit more where on cvs but mine have been fine even with lowered car.

[gmccormack 0]

Difference is the disc/drum t/a's

The disc'd t/a's are offset for a 8 bolt diff and the drum brake ones are offset for a 6 bolt.

Are you sure about that?? As there are rear disc cars that have small case diffs, ie. higher spec 316/318 yet their arms interchange with a 325 which all have medium case diffs

[will 169]

Are you sure about that?? As there are rear disc cars that have small case diffs, ie. higher spec 316/318 yet their arms interchange with a 325 which all have medium case diffs

I was thinking the same thing, will attempt to check it out with my fleet sometime. I would think the diff mountings vary on the subframe. I am pretty sure the arms are the same between drum and disc as I have on occasion simply swapped drum for disc without changing the subframe and havn't noticed the wheel move further to the rear of the wheel arch.

Edited April 24, 2007 by will

[ED1RTY 2]

hmmm yea as you said Will the wheel doesnt move back in the arch.

Maybe my cars etc are retarded and have munted subframe/arms

This is all really wierd!!

[Mike 1]

I was thinking the same thing, will attempt to check it out with my fleet sometime. I would think the diff mountings vary on the subframe. I am pretty sure the arms are the same between drum and disc as I have on occasion simply swapped drum for disc without changing the subframe and havn't noticed the wheel move further to the rear of the wheel arch.

Let us know what you find Will, I don't think it will be the subframe though, its the same part no. between all models that we got.