Drive shaft help

[fbirch]

I decided to replace the OEM drive shaft in my '99 M3 race car. I ordered one of the rebuilt drive shafts from Turner, which are modified to include replaceable U-joints, unlike the OEM shaft. Turner offers two models for the E36, one for the '95 and one for later E36 cars. The later shaft is shown on their website as having two U-joints on the rear segment of the driveshaft and no U-joints on the front segment of the shaft, just like OEM for later cars. It also has the 4-bolt diff flange for the later cars.

When I opened the box I saw a drive shaft that has one U-joint on the aft end of each half shaft (like the pictures they show for the '95 M3 shaft), yet it has the correct 4-bolt diff flange for the later cars. It looks like a hybrid of the '95 and later drive shafts. Also, the center support bearing on the Turner shaft has a bracket with holes that are too close together to mate up with the studs on my '99. I could replace the CSB with one that will bolt up to my car, but I'm concerned about all the other differences.

Please see the picture of my OEM shaft (top) and the one I received from Turner (bottom). So far, Turner hasn't been able to get an explanation from the shop that does the rebuilds for them, Beyer Motor Works. What do you guys think, should I replace the CSB and use the new shaft or insist on one that replicates the original in terms of U-joint placement?
Driveshaft comparo.jpg

[pbonsalb]

Interesting. I am curious as to the explanation; I don’t have one or an answer for you except that if it fits and everything bolts up it should work. Might get a faster response in the E36 or E36 M3 subforums.

[aeronaut]

My 95 originally had a CV joint (and 6 bolt flange) in the rear of the drive shaft. I F'd it up pulling the differential once (busted the boot on the CV joint). I switched to the U-joint/4 bolt flange version (96+). No issues. But that's slightly different than the weird case you have, I think.

[emoore924]

Ok, dumb question..., why do you have them reversed for the comparison? Looks like the ends are swapped. It would be easier (for me anyway) to have the front of one driveshaft matched to the front of the other and the rear to the rear.

Other than that, I got nuthin

[pbonsalb]

You can’t attach the 3 bolt flex disk end to the diff and you can’t attach the 4 bolt diff end to the flex disk.

The only thing I can think of is that maybe parts from other cars were mixed and matched to give the correct length, and/or the flanges were cut off and welded back on after shortening other shafts and someone mixed up the flanges.

[aeronaut]

Yea, taking a closer look at that pic, that's F'd up. I would think both U-joints must be on the same (rear) half-shaft, like the original.

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My previous statement is untrue, realoem shows the CV joint driveshaft and the ujoint driveshaft having the middle ujoint on different half shafts. Hmmmm.
Anyway, back to pbonsalb's statement.

[aeronaut]

Ok, I'm not sure what you have won't work. Look at the pictures of the 2 driveshaft types in realoem.

Attachment 664766Attachment 664767

[fbirch]

Ok, dumb question..., why do you have them reversed for the comparison? Looks like the ends are swapped. It would be easier (for me anyway) to have the front of one driveshaft matched to the front of the other and the rear to the rear.

Other than that, I got nuthin

In the pic I posted, the guibo end of each shaft is on the left and the diff end of each shaft is on the right. They are aligned consistently, but they LOOK different because the joint arrangement is so different.

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You can’t attach the 3 bolt flex disk end to the diff and you can’t attach the 4 bolt diff end to the flex disk.

The only thing I can think of is that maybe parts from other cars were mixed and matched to give the correct length, and/or the flanges were cut off and welded back on after shortening other shafts and someone mixed up the flanges.

Turner has contacted the rebuilder and they've told me to return the shaft without explicitly detailing what's wrong with it, but acknowledging that it's not correct for my car.

- - - Updated - - -

Yea, taking a closer look at that pic, that's F'd up. I would think both U-joints must be on the same (rear) half-shaft, like the original.

- - - Updated - - -

My previous statement is untrue, realoem shows the CV joint driveshaft and the ujoint driveshaft having the middle ujoint on different half shafts. Hmmmm.
Anyway, back to pbonsalb's statement.

I can't see the attachments in your email below, but the pics I saw online and on Turner's website show the 96+ shaft as having both U-joints on the rear shaft. My garage partner has a '97 M3, and his drive shaft is the same as the one on my '99: Both U-joints are on the rear shaft.

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Thanks to all who replied here. The rebuilder has promised to do a quick turn on rebuilding my OEM drive shaft and Turner is taking back the incorrect shaft, so I'm satisfied with the customer service of both companies.

[pbonsalb]

But all you need is the correct length and the shaft will work. You write that the only issue is the CSB bracket holes are too close together to fit the studs on the chassis. Is there any flex in the CSB to open it up so it fits the studs — it’s a rubber isolated bearing as I recall (my E36 and E90 M3s use one piece DS so I may be forgetting how the CSB works)? If not could you elongate the slots enough to fit or make little spacers easily? Unless it was easy, I obviously would not bother and would instead return the shaft for the correct one.

[fbirch]

But all you need is the correct length and the shaft will work. You write that the only issue is the CSB bracket holes are too close together to fit the studs on the chassis. Is there any flex in the CSB to open it up so it fits the studs — it’s a rubber isolated bearing as I recall (my E36 and E90 M3s use one piece DS so I may be forgetting how the CSB works)? If not could you elongate the slots enough to fit or make little spacers easily? Unless it was easy, I obviously would not bother and would instead return the shaft for the correct one.

The CSB bracket on the new shaft is not close enough to be able to be modified to work on the later cars, the holes are significantly too close together. I could probably slide it off the splined shaft and slide on a CSB with the correct bracket, but I'd rather have the correct shaft for my car. I agree with you that I could probably get away with using the new shaft, but it would bother me knowing I had the option to get the correct shaft but settled for something that doesn't match any known configuration I've seen before. There must have been a reason BMW changed the design of the shaft with different U-joint placement for the later cars and I'm not inclined to second guess them.

[pbonsalb]

I have been second guessing bmw for 15 years. Have a different engine, driveshaft, differential, transmission, shifter and linkage, suspension, fuel system, tune, etc. But for most people stock is fine and simplest.

[fbirch]

I have been second guessing bmw for 15 years. Have a different engine, driveshaft, differential, transmission, shifter and linkage, suspension, fuel system, tune, etc. But for most people stock is fine and simplest.

LOL, you have a point (** admits the guy with the modified racecar)

[pbonsalb]

But for this, I agree it’s easier to get the seller to correct the problem then for you disassemble the shaft, buy and press on a new CSB

[jakermac]

That shaft on the bottom would likely lead to vibrations in the drivetrain (at the very least) and possibly some serious issues (depending on angles). Both u-joints need to be in the same section of the shaft to allow for proper driveline/u-joint angles. Otherwise you would most certainly end up with vibrations.

[aeronaut]

That shaft on the bottom would likely lead to vibrations in the drivetrain (at the very least) and possibly some serious issues (depending on angles). Both u-joints need to be in the same section of the shaft to allow for proper driveline/u-joint angles. Otherwise you would most certainly end up with vibrations.

I want to agree, but, from realoem.

DS.jpg

[fbirch]

I want to agree, but, from realoem.

DS.jpg

Weird. That pic shows the 4-bolt diff flange for the later cars, but it doesn't match the shaft that's in my '99 or my buddies '97, both of which have the original shafts. My '99 was one of the last E36 M3s built. I wonder if BMW changed the design of the driveshaft after the car was out of production? That picture matches what I got from the rebuilder. Now I'm really confused!

[pbonsalb]

There are some little known changes, like wiring harnesses that don’t require the crank sensor subharness. Not sure about driveshaft but you said it does not fit the CSB studs on your chassis. Those are fixed and not easily changed so it’s unlikely bmw changed the DS to one that requires custom work to fit.

[fbirch]

There are some little known changes, like wiring harnesses that don’t require the crank sensor subharness. Not sure about driveshaft but you said it does not fit the CSB studs on your chassis. Those are fixed and not easily changed so it’s unlikely bmw changed the DS to one that requires custom work to fit.

The stud hole spacing on the CSB bracket is wrong for sure, but I'm wondering if BMW changed the U-joint placement for replacement shafts after the car was out of production. I'm wondering if the rebuild shop got the U-joints right, but simply pressed on the wrong CSB assembly (maybe the early cars have the studs closer together and they just installed a '95 CSB assembly, for example).

[aeronaut]

And just by chance, currently helping a friend change the clutch in his 2000 E46. The front half shaft, with one U-joint, below.
I agree, it seems it'd be better to always have the 2 u-joints on one side or the other of the CB, but BMW doesn't seem to care.

.IMG_20200111_120758.jpg

[jakermac]

I stand corrected, but that's just nutty. Maybe the giubo counts as a u-joint when it comes to driveshaft/u-joint harmonics?

[pbonsalb]

Yes, the flex disk takes the place of a front joint.

[aeronaut]

I stand corrected, but that's just nutty. Maybe the giubo counts as a u-joint when it comes to driveshaft/u-joint harmonics?

I don't understand it either! They decide they need 2 u-joints (of course), why not always put them both on the same half-shaft. The CSB does have a fair amount of non-concentric movement, so the half-shaft that goes through the CSB can move up/down a bit. Plus yea, a little flex in the guibo. But still. I guess it works. lol.

[fbirch]

I spoke to another driveshaft supplier who said that pictures on realoem are not always exactly precise for a given part and model of car, particularly in cases where many different iterations of that part exists for different variations of the same car. I have no idea if that's correct, but he has a rebuilt '99 M3 driveshaft in stock and it looks exactly like my original - two u-joints on the rear shaft and a fattened tube section on the front shaft.

[NeilM]

I spoke to another driveshaft supplier who said that pictures on realoem are not always exactly precise for a given part and model of car, particularly in cases where many different iterations of that part exists for different variations of the same car. I have no idea if that's correct, but he has a rebuilt '99 M3 driveshaft in stock and it looks exactly like my original - two u-joints on the rear shaft and a fattened tube section on the front shaft.

His comment about the drawings is not only correct, it’s an understatement. Some of what they show is not even close to reality — and those are BMW drawings.

Neil

[TheJuggernaut]

The bottom one looks like an E30 driveshaft. They have the splines on the opposite ends, and the CSB even looks like the late E30 style bearing.