Driveshsaft Question - non BMW rear diff

[DaveKern]

Hi all,

I'm working on finishing off my rally build and have a question about driveshafts. I've read up on all the different threads about lengths and different flanges at the diff, etc. but still have a question.

I'm using a 1995 S50 motor and tranmission.

At the back of the car will be a Toyota Supra Mk III diff (4.56 for those who are curious).

Because of the toyota rear diff, I'm 99% sure that I'm going to have to get a driveshaft shortened and will likely have to re-drill the bolt pattern. So, with some customization in my future, I'm wondering if I need to be as picky about the driveshaft I source?

From what I can tell, the only length I really need to be concerned about is the distance from the guibo to the spot where the carrier bolts to the bottom of the car, that way I'll just have to get the rear of the driveshaft modified.

So, if my assumption holds true...are there any other driveshafts I can consider than the 1995 M3 one? The engine and transmission are not in my car yet so I don't have the ability to measure that distance, but if I have to get parts shipped in, it'd be great to do that now so I don't have to pay for rush shipping once the motor/trans is back in.

I've got a 1997 Z3 2.8 and another 1997 Z3 (engine unknown ATM) that are both within driving distance of my house and reasonably priced. Any chance one of these could work?

Thanks,

Dave

[DaveKern]

So it turns out I won't be able to have all the parts needed to pull off the Supra swap as the car goes back together. This will get put on the back burner until springtime.

So now, my solution will be to use the small case diff with my 1995 M3 engine & transmission. I've got an open 4.44 diff which I'm going to have welded up so I can actually get somewhere in the snow. **I know this is not a good long term solution and I will likely blow the diff.** I'll only be using this to get through the winter, and the only time I'll be beating on the car is on ice-covered tracks, so there's really no chance of shock-loading the diff in any meaningful way.

With the disclaimer out of the way, the problem I seem to be running into is that every M3 driveshaft I see for sale is the 6-bolt one (CV style), and I need a 4-bolt.

I did quite a bit of searching and have found some useful info. I beleive that the M3 and 328 both use the same transmission.

Originally Posted by J!m

328i / M3 = 1492mm
(these have different part numbers, and the M3 drive shaft comes in 2 flavors, U-Joint and CV joint)

So, since J!m's info seems to confirm that both use the same length driveshaft, would I be able to use a driveshaft from a 328 since I think that the 328 only used a 4-bolt rear end?

Thanks,

Dave

[pdxmotorhead]

If'n it was me, I'd take the yoke that matches the rear, the driveshaft that matches the front and go to a driveline shop and give them the 120 bucks to make them one..... LOL

Keep teh two piece drive line, if you convert ot a 1 piece you'll likely get wicked harmonics about 50 MPH at random speeds based on the resonance of the drive shaft.

Dave (Other one...)

[DaveKern]

Originally Posted by pdxmotorhead

If'n it was me, I'd take the yoke that matches the rear, the driveshaft that matches the front and go to a driveline shop and give them the 120 bucks to make them one..... LOL

Keep teh two piece drive line, if you convert ot a 1 piece you'll likely get wicked harmonics about 50 MPH at random speeds based on the resonance of the drive shaft.

Dave (Other one...)

Problem is I don't have a driveshaft for the transmission yet. My swap only came with the engine/trans/wiring, so I have to buy some sort of driveshaft because the only one I have is from an automatic ti.

I'm trying not to spend get into custom work twice if I can help it. I figure the elusive M3 4-bolt rear (& maybe 328) will fit my current setup with no mods, so I could use to get thru the winter, then get the custom work done when the Toyota unit goes in next spring.

Dave

[pdxmotorhead]

Ah that makes sense, have you asked the drive-line shops? the one I use will build one from scratch for 250 or so, and do it in Aluminum for many....

Of course I don't know how bad the yokes for the Guibo are...
But maybe you could spec a std Spicer u-joint in the middle that would be cheaper

Cheers


Dave

[DaveKern]

Originally Posted by pdxmotorhead

Ah that makes sense, have you asked the drive-line shops? the one I use will build one from scratch for 250 or so, and do it in Aluminum for many....

Of course I don't know how bad the yokes for the Guibo are...
But maybe you could spec a std Spicer u-joint in the middle that would be cheaper

Not really in a position to do anything yet, as I suspect a shop will need the car there in person, or would need a driveshaft that I'd say "build me one to replace this" kinda thing.

I do know of a shop locally that will build custom stuff, but IIRC they were getting near $600 for an aluminum one for an Evo. I don't want aluminum since it gets pitted up so quickly from rock blast, but a lightweight chromoly one would be pretty sweet.

Dave

[3.2TI]

I know you mentioned you are not trying to spend on custom, just wondering what you are willing to pay for a 328 or m3 driveshaft because I have a few places that you can get it from. the only thing is that they are not cheap and you will have to be sure of part you need.

I recommend you get the vin from the engine and type the last seven into realoem.com and look for the driveshaft part# that came with that car. Then you should do a reference on the part to see what other cars may have that part. This could help you find it easier with the right part number. If I am not mistaken all sedan and coupes are the same length but I could be wrong so check that as well. Remember that buying a used driveshaft requires a new Guilbo since most either don;t include it or is too old and worn to use. Expect to pay in the range of $200-400.

[DaveKern]

@ 3.2TI: trying to source used shafts from non-rust regions of the country. Have found many on ebay or Bav Auto for ~$250 or less. My main problem is trying to figure out what I actually need. Agreed that it'll be a good idea to replace the guibo on any used purchase.

I did some more digging. Turns out the 1995 M3 is a bit unique:

1995 M3 1469mm
1996-99 M3 (& 328) 1492mm
1995 325 1512mm

The problem is that I beleive that the 1995 M3 only came with a 6-bolt rear end, and I'm trying to use a 4-bolt (both OEM and Supra diff). I guess the next question is that when I look at these driveshafts I see that the splined middle section allows for some expansion. Wondering if these usually have 23mm of splines showing...because if they did, I suppose the longer 4-bolt shaft of the 328 could work.

This also has me wondering if I might be able to mix-n-match driveshafts. Maybe I could use a 1995 M3 front and a 328 rear section?

Dave

[wolferj-RIP]

Mix-n-match is fine... the M3 front/328 rear is a perfectly fine combo.

[DaveKern]

Originally Posted by wolferj

Mix-n-match is fine... the M3 front/328 rear is a perfectly fine combo.

Cool! Any idea if M3 front and 318ti rear (from automatic) would work too?

If that combo won't work, any idea if the rear section of an automatic 328 would mate up to a 1995 M3 front? I found a 328 auto one for sale locally for a good price. I fiugre if I'm only using the front of the M3 and the rear can be from something else, maybe the rear of the 328 auto & manuals are the same?

Dave

[wolferj-RIP]

I suspect that combination could end up being too long... (but not necessarily) Measuring would be the only way to know for sure.

[DaveKern]

Originally Posted by wolferj

I suspect that combination could end up being too long... (but not necessarily) Measuring would be the only way to know for sure.

Gotcha. I kind of figured it might be the front section of the driveshafts that would be different, as the carrier bearing always needs to mount to the chassis in the same spot....but maybe it doesn't?

Just got word that my buddy finished giving my OEM small diff the "Lincoln Locker" treatment, so I should be able to get that bolted back in and take measurements by next weekend.

Dave