M Coupe Chassis Closeness?

[slacker]

I want to do the same rear end swap. The whole rear suspension; diff. brakes, subframe, swaybar, but want to keep my Bilstein PSS9 springs/shocks and it seems from the posts, parking brake cable. What's the latest on the drive shaft? Use the original? I assume the rear brakes and calipers would be MCoupe as well, but what about the subframe mount? Does it bolt up or do you have to mod the stock subframe? And last but not least, which axels? Ti or MCoupe and do you need mods to the these and if so, what? We have an MCoupe and I could look at the items to compare but want someones experience to go on. I already know about the spare tire needing deflating to clear the finned diff. cover. Thanks for any input.
Gary

[Uber E30]

Gonna bump this, going s52+ZF and have access to a 2.8 z3 driveshaft... anyone know if it fits or do i need to bastardize an m3 shaft?

[cooljess76]

Originally Posted by Uber E30

Gonna bump this, going s52+ZF and have access to a 2.8 z3 driveshaft... anyone know if it fits or do i need to bastardize an m3 shaft?

I think one thing you might run into is that many Z3's have 6 bolt differential input flanges.

[Uber E30]

No problems there, im getting the 3.15 torsen diff from that z3 so whatever it is will match.... just concerned about the legnth.

[J!m]

Z3 drive shafts are too short for the ti.

If you mix-n-match driveshaft parts, as some seem inclined to do, have the entire new assembly balanced.

You can probably change the input flange for the diff if you had to; however I have an M Roadster diff and it has a four bolt input flange. I have not seen any Z3 diffs with the six bolt flange, but that does not mean they didn't exist...

[Uber E30]

Originally Posted by J!m

Z3 drive shafts are too short for the ti.

If you mix-n-match driveshaft parts, as some seem inclined to do, have the entire new assembly balanced.

You can probably change the input flange for the diff if you had to; however I have an M Roadster diff and it has a four bolt input flange. I have not seen any Z3 diffs with the six bolt flange, but that does not mean they didn't exist...

I might be mixing you up with someone but, I though you had a g250? Have you tested the length with a ZF as well?

[J!m]

Yes, I still run the Getrag and it is fine after many years of service. I am not inclined to change it 'for fun' but rather for a six-speed only.

The ZF from the M3 is a bit longer, and therefore the driveshaft is shorter. Even on a car like mine (swapped with the Getrag) you need to use a shorter drive shaft (325 shaft), but can get away with the ti one (i am running the ti shaft in my car as well).

If you use a six and the M3 ZF tranny, you need to use the M3 driveshaft with it. If you have a four and the M3 tranny (???), I suspect the 325 drive shaft would be the right one, but the correct solution is to measure from the output flange to the input flange and get the correctt length shaft. I have a cross reference chart in my swap manual to avoid any issues with all the possible tranny, engine and diff possibilities.

[Raphie318ti]

J!M ....im halfway through my 2nd s50 swap right now...when i did my 1st s50 swap into my daily driver, i changed everything in the car.... at the time i had the cash to re do everything so that means ...suspension...differential..axels...tranny..engine..braking system ...exhaust system etc... i dont have that much money right now but i do have another 318ti in my garage with a working Getrag stock tranny but blown engine....my question is...if i do buy another s50 engine ..will it match up fine with that transmission ? and if so can i keep the driveshaft and differential or do i have to change it? and can i keep everything stock from a ti when i do the swap except the engine......

[Ragnorak]

The Getrags are compatible if you're low on funds. The ZF 5-speed is a proven stout transmission and has a higher torque rating. I'd recommend a fluid change on the transmission and differential an try not to beat on the car when launching.

To the original question, any MZ3 is a great donor car for the 318ti. However, they're very hard to come by. Try to find one with minimal front/side damage. You want the rear end to be in good shape without suspension damage. Otherwise you might as well have bought an M3 donor.

Driveshafts are easy to come by and can be had for $100-$150. The rear suspension and drivetrain from the MZ3 is much more expensive and really is the driver for using that donor vehicle.

[J!m]

Originally Posted by Raphie318ti

J!M ....im halfway through my 2nd s50 swap right now...when i did my 1st s50 swap into my daily driver, i changed everything in the car.... at the time i had the cash to re do everything so that means ...suspension...differential..axels...tranny..engine..braking system ...exhaust system etc... i dont have that much money right now but i do have another 318ti in my garage with a working Getrag stock tranny but blown engine....my question is...if i do buy another s50 engine ..will it match up fine with that transmission ?

Yep. No problem.

Originally Posted by Raphie318ti

and if so can i keep the driveshaft and differential or do i have to change it?

Drive shaft is open to debate. I kept mine, but it is a touch too long. A 325/328 drive shaft should be a better fit.

The diff absolutely must e changed. It WILL break; the only question is when. Often it fails without warning.

Originally Posted by Raphie318ti

and can i keep everything stock from a ti when i do the swap except the engine......

No, the front suspension must be up-rated for the increased load. Also, the brake system must be upgraded to stop the heavier and faster car. Rear suspension can remain as-is, but the front should be replaced with the M3 donor car parts.

[pdxmotorhead]

The E46 Front brakes are easier/cheaper and bigger.. If your swapping in the rear subframe of the M coupe its a match made in heaven. All stock parts, and not specialty M bits.

Dave