NEED HELP swapped drive shaft

small_m · 05-25-2010, 02:18 PM

Long story short, I took my car apart to add a euro 6sp trans to mate to my s50. At the same time i added an e30 diff. I had the front half of my driveshaft shorterned as the 6sp is longer. I always remember my driveshaft being alittle on the tight side before, but now it doesnt fit at all. If i split the 2 halves the front section is a perfect length, but the rear is too long. I bought the car with the s50 already installed so i am not sure about the driveshaft. Could it be i have an m3 driveshaft? I am unable to figure out what to do with the rear section.
Could someone please measure their rear driveshaft from the front u-joint pin center to the rear.
Mine comes out to exactly 30inches. Is this a ti rear section or an m3?
Thanks

small_m · 05-25-2010, 03:36 PM

I found this picture that i took of the e30 and the ti diffs next to each other. it seems like the e30 nose sticks out further than the ti. This might explain my driveshaft issue. I have not heard of anyone having this issue!!! Can anyone confirm?
Thanks

small_m · 05-25-2010, 06:00 PM

ideas anyone?

**wolferj-RIP** · 05-25-2010, 06:32 PM

What is the diameter of the rear shaft section? That would tell you if it was from the ti or from the donor M3. I suspect it is from the ti, as it has the 4 bolt pattern. I believe that several members have used the hybrid of M3 front/Ti rear driveshaft combo to make it work. I cannot recall whom, however. I did not swap trannies (still running the Getrag with my M50) so I cannot be more definitive, sorry...

small_m · 05-25-2010, 06:36 PM

from looking at all the pics from realoem it seems to look like a ti rear section. I am going to try removing the diff bolting up the driveshaft shaft and then installing the diff, i cannot push the driveshaft "over center" as its too long. I wonder that if i can get it up in the tunnel first it might fit better. I am confused as noone as had this issue.
Is the e30 diff slightly longer?

**wolferj-RIP** · 05-25-2010, 07:16 PM

Your approach to fitting the diff after getting the driveline in place sounds very reasonable. I seem to recall a couple of members had this problem, but were able to overcome it by combining parts. I will search to see if I can find the thread about that.

I am unsure if the two diffs are different lengths where it counts, but with so many people running swapped diffs, it shouldn't be a concern.

One note of concern is the center bearing. If there is too much forward pressure on this, it will wear out very quickly.

small_m · 05-25-2010, 07:21 PM

well i will give it a go tonight. I am keeping my fingers crossed as i have been working on the car flat out for a few weeks now and would like to get back to driving it. Plus i am about out of money now lol.

**wolferj-RIP** · 05-25-2010, 07:39 PM

good luck, keep us posted.

chrisbec · 05-26-2010, 01:57 AM

From the photo you took you are using the ti rear section (just reconfirming what you already said earlier). It is easy to spot since it is skinny.

The ti rear section should locate the carrier bearing correctly when it is bolted to the differential flange. In other words the carrier on the front of the rear ti section should align with the mounting points on the body. I am running an e28 (medium case like the e30's) differential and a the rear section of the ti drive shaft and all of that fits together and aligns for me with no problem.

Did you try loosening the nut behind the carrier bearing to see if you can make the drive shaft a little shorter (see the attachment)? This compression nut squeezes a plastic sleeve over the splines of the drive shaft. If the drive shaft was balanced you should not separate the forward and rear sections unless you mark them so that you can align the splines and put it back together in exactally the same orientation that it came apart...

roadrash · 05-26-2010, 05:34 AM

Have you seen these two threads?

Differential parts compatibility - DISCUSSION

Differential parts compatibility - LISTINGS ONLY

Maybe you'll find a suggestion or idea in there?

small_m · 05-26-2010, 04:18 PM

Yes i have seen the threads. The driveshaft is as short at it can get right now. I did find that I did not have clearance from the top of the diff to the underneth of the car. I found some posts of others having to modify the floor. I did manage to do that and it got me a lot closer. The rear "ear mount does line up but the subframe seems like it is too far forward and does not line up. I might try dropping the subframe off the mounts and bolting the diff to the subframe and raising it up all together. Other than that i have no idea what is going on. And yes the center support bearing lines up perfect with the mount. the front half is also perfect.
Strange!!!

small_m · 05-26-2010, 07:00 PM

Another idea i had is to remove the locking nut allowing my to shorten the drive shaft more. I am wondering if this is a good idea. If you look at a euro 6sp M3 driveshaft it does not have this lock nut. It just has splines that fit together. The only thing holding it together is that it is the correct length.
Thoughts?

**cooljess76** · 05-26-2010, 07:21 PM

Since there's not many Ti's with 6spd swaps, it's gonna be difficult find info. Here's an idea, assuming at this point in the game you're gonna need to have the driveshaft rebalanced anyway, why not have a machine shop shorten/lengthen it?

small_m · 05-26-2010, 07:29 PM

The thing that is killing me right now is that i just paid ($250) to have the front section shorten and the entire driveshaft balanced. I spent alot of time measuring and compairing to be sure of the correct needed length for the front half of the drive shaft. This is the same drivesahft i used with the 5sp. It was also a very tight fit (more so when i added the ireland engineering subframe bushings, i am guessing because the old bushing were allowing the subframe to be pushed back). So i had an extra 1/4inch taken off for a total of 4 1/4" removed from the front end. The front end fits perfect and lines up with the mating of the rear section and the center support bearing and is the same length as the front half of the euro driveshaft (seen in picture). It still seems like the rear section is too long which is hard to believe as its a stock ti rear part. Its almost like the subframe is too far forward!!

small_m · 05-26-2010, 08:32 PM

so after looking at this pic i found on line I would have to say that my front section is still too long and must be shorter for things to fit correct. I have no spline showing and the spline nut is almost touching the center support bearing. Now its going to be an expensive old driveshaft

Damn it!!

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