BMW M70 Manual 6spd Drive Shaft Failure at The U Joint...

[bmw528e11]

Don't even know where to start..
From the first day of owning my e31, it had vibration even on idle, replaced just the motor mounts.. it got little bit less, but still it had the mount failure feeling, after driving it for 5 months, i finally decided to replace transmission mount (it looks the same as the engine mount, but just upside down) After replacing transmission mount, all that mount failure vibration was gone!

Driving for another month, started noticing a clanking sound, every time when changing driving direction forward or reverse (sometimes it would make same sound when shifting from gear to gear and letting the clutch pedal too soon) at the same time, 40 MPH hard vibration appears and disappears after 40mph.

So, here's a link what i found out when lifted my e31 on the hoist:

P1 https://www.youtube.com/watch?v=VzzsQyr8sjk


When out of the car

P2 https://www.youtube.com/watch?v=RwEsN4L8dpY


Great! I found one drive-line repair facility, who build custom drive lines for drag racers and off roaders.. They looked at my drive line, and quoted me $525 for full rebuilt and installing a new drive line support bearing ($150). I found support bearing from my parts suppliers for $50. Brought them my support bearing. After a day, they called me and said that its READY!! Woohoo!! Came over, and saw new weights at the front and rear portions of drive line (so, they balanced it at the same time, i think..) They even painted it, looked like a brand new drive line!! I thought it will last me for another 167k miles!?

Ye Right! Not so fast!.. Brought it over to my place and noticed that the CV joint rubber boot is taped up with electrical tape.. 'hm, they forgot to remove it after painting it over' i thought.. but no, they tried to hide a 1.5 inch cut!! I called them, and they started blaming me that i did the damage.. so i didn't complained much (i didn't took pictures prior repairs) So i just quietly ate my damaged CV joint boot, and tried to install the drive shaft back to the car.. what you know, the bushing #1 is bigger inside diameter then what the "drive line experts" installed..

http://realoem.com/bmw/enUS/showpart...diagId=26_0094

Anyways, bought the original bushing from my dealer for only $17, brought the drive line back to the rapair facility for the bushing replacement. instead of the refund of the bushing they installed, i asked for a cold bottle of water.. they gave me TWO bottles, isn't that nice of them.. lol

Finished installing my drive shaft, took it for a spin. no clunking sound, no vibration at 40mph Woohoo! its fixed!

Two days later.. went on meet up with my mates after the meet, I wanted to show off with my 850i how it can accelerate from a stop light.. raved it up, and dropped the clutch.. lol next thing you know, I'm calling the towing because something snapped near the support bearing.. My flashers did came on with air bag module disconnected?? (Well, drive line facility gave me 90 days warranty for parts and labor..)

It turned out, their U joint snapped.. The asked me; "just curious, what were you doing with your car!?" I told them "i was standing on the stop light, with a V12 and saving gas... what else could i've done.." lol..

after they had my drive line for day, they couldn't find a core, so they had to build a custom one.. Whats left from my drive line was the the bushing with front flange and a rear Cut CV Joint..

I apologize for making the big story, for low quality pix and for not taking pictures of their new, special built, drive line..



IMAG2206.jpgIMAG2209.jpgIMAG2211.jpgIMAG2213.jpgIMAG2214.jpg

[bmw528e11]

IMAG2216.jpgIMAG2217.jpgIMAG2218.jpgIMAG2243.jpgIMAG2245.jpg

[dragon850]

Glad you got it sorted, I just bought the entire remanufactured drive shaft for my old green 850 when I got vibration. Had it replaced and had no issues till I sold it 20k miles later.

[mattsimis]

Why did the first U-Joint fail and why will the second one not fail...?

[affa]

Just wondering, if they replaced the u joint what did they replace it with? The original ones are staked. And the only ones I can find are rockford....

If they also used rockford then I've got some thinking to do.....

Can you send me some Hi res pics? Especially the u joint and the broken bits. I want to see what failed first. Looks like the u joint yoke also snapped? No?

[bmw528e11]

http://pages.ebay.com/motors/link/?n...392217&alt=web

It looked similar to this one. I thought it seems to be thinner compared to stock..

Unfortunately, no high resolution pictures.. only cell phone pix.. Grr... Actually that's a must, to have a good res. camera when owning an 8.

[affa]

Dana is a decent brand... I'm surprised it gave way so easily. I would love take a look at the damage to see what kind of fracture it was...

Well yes the factory yoke (when I took it off) does seem to be a bit meatier. Also its not greasable. I wonder if the holes (for greasing) contributed to the failure.

A few questions / observations:

1. The link you referred to, is that the exact model of the u-joint they used? if not which one? I've got a hunch but I need the dimensions.
2. From the pic it does look like the fracture originated from a crack on the centre yoke, but its only a guess without better pictures.
3. The forks looks bent as well? can you confirm? Hard to tell what gave way first, the forks or the u-joints?
4. The holes on the forks where the bearing caps should be looks suspiciously clean and smooth. Did they enlarge the holes to fit the DANA unit?

Even though they are made from forgings, there aren't a lot of meat on the forks. I would be very weary about taking any material off, a LOT of Nm are going through them.

[bmw528e11]

A few questions / observations:

1. The link you referred to, is that the exact model of the u-joint they used? if not which one? I've got a hunch but I need the dimensions.
2. From the pic it does look like the fracture originated from a crack on the centre yoke, but its only a guess without better pictures.
3. The forks looks bent as well? can you confirm? Hard to tell what gave way first, the forks or the u-joints?
4. The holes on the forks where the bearing caps should be looks suspiciously clean and smooth. Did they enlarge the holes to fit the DANA unit?

1. The link i posted above, was the yoke that looked as they installed it in the first place, they didn't give me any documentation what brand or size, just the amount i owed. lol
2. If the yoke broke, it should've broke on both sides? but as i dropped the clutch pedal, i left 1.5 meters of two stripes on asphalt and then something broke..
3. Yes, one of the forks is bent.
4. Don't know, it does seems its polished out.. don't know what they did and how..

But now i sitting and thinking through. you right, one of the forks were twisted off, in my opinion that's when a yoke snapped off when it started bending one of the forks... so, i think my yoke shifted to one direction and came out of the opposite fork.
Why? they used their own yoke, that had a clip on the inner side of the fork.. on the picture you can tell they modified (grinned) some materiel from a fork to install their retainer clip...

IMAG2213 P2.jpg

IMAG2304 p.2.jpg

Second picture, drive shaft from '97 850ci Auto

[affa]

The factory uses staked u joint as in your last picture. The only way to reman it is to replace it with u joints using inside circlips. Pretty common procedure. See you can see from the link, this include some cars that can see some stupid power modded.

http://rockforddriveline.com/Staked-In_U-Joints.pdf

Possibilities:
1 - Manufacturing defect - the trunion ( the 4 grounded round ends on the cross journal / yoke) had a crack on it already. But the small movement caused by a minor crack would have been taken up by the other 2 or 3 trunions. Like your original shaft before repair.

2 - an oversized u joint was used and too much material was taken off the fork to fit the u-joint. The fork bent under load, essentially twisting one of the trunion off.

3 - as you said, they might have taken material off to make room for the circlips, created some stress raisers. Same result as 2.

4 - they bent the fork while pressing out the old bearings, bent it back, possibly with heat, weakened it.

5 - they forgot to put in the circlips, the yoke/cross journal shifted off centre under load and threw the balance off, then bad things ensued. (I can't really see the clips in place on the surviving bearing caps in the pictures).

6 - even if they had put in the clips, normally they have to Centre the u joint by eyeball as the circlip to circlip axial distance is usually smaller than the fork inside width. If it's not a good mechanical press fit or some retaining compound is not used, you can get the same result as 5.

My leading theories are 2-6, 1 shouldn't cause what we are seeing.

Sorry for the long winded post. I'm in the middle of changing the u joint myself so I'm interested in getting to the bottom of this. However without better pictures all I'm doing is speculating.

- - - Updated - - -

Why did the first U-Joint fail and why will the second one not fail...?

I believe the manual only has one u-joint. as does the M73 autos. IIRC only the M70 autos have 2 u-joints.

[affa]

Sorry for hijacking this thread. But I think its very relevant info for everyone to put into this thread rather than another one. Once we get to the bottom of this I'll post a new DIY shaft rebuild thread.

My u-joint was notchy, not something you can feel while driving but I had it out of the car so I was curious. It felt like almost like it had a designed detent. I took it apart and it was evident that the seals were history and although all the needles were still there all the grease had gone hard and gritty. Here you can see the dried up grease in the bearing cup and the wear on the trunion and why it was notchy...

DSCN0565.jpgDSCN0582.jpg

Our E31 have what's called a staked-in u-joints and the factory would tell you its unserviceable. So having looked around the net I found Rockford drivelines claims to have us covered. E31 was not specifically stated but the E32 750i was, close enough, they have the same staked-in u-joints.

http://rockforddriveline.com/Staked-In_U-Joints.pdf

So I finally received the joints and its likely its the same types the OP's rebuilder used (might even be the same). here are some comparisons...

DSCN0578.jpgDSCN0579.jpgDSCN0580.jpg

The factory on is on the left. First you can see the trunions of the aftermarket joint are substantially smaller in diameter. More than 4.5mm less and that's a lot. This is necessary so that there's enough meat on the bearing caps for the retaining ring groove.

picture upload limit. to be continued.

[affa]

Below are more comparison pictures:

DSCN0581.jpgDSCN0583.jpgDSCN0584.jpg

Here you can see the factory one (right) is a lot meatier in cross section. also its not drilled through the middle and hence non-greasable. More concerning is the width of the cross journal. You can see the factory one is 70mm and the aftermarket one is a hair under 60mm, again that's quite substantial.

I have to say I'm a bit disappointed.

Putting aside the trunion diameter and the journal thickness aside for a moment (neither is good from a performance standpoint). I think the most disappointing thing is the journal width is a full 10mm narrower. Take a look at the following picture I took for the eventual DIY thread:

DSCN0560.jpg.

Here you can see the bearing cap on the right hand side still in the fork. It hasn't been moved yet (the seal had crumbled away) and you can see how little meat there is on the fork to retain the bearing cap. Now being full 10mm shorter (5mm less each side), There simply isn't enough of the trunion and bearing cap being retained in the fork. Especially when the rebuilder machine away the forks to make installing the clips easier as I suspect is what happened to the OP.

So here's what I think happened. The forks were machined to make the clips fit (that's why they had to rebalance it I think). With the narrower cross journal and bearing caps of the aftermarket unit, when the clutch was popped the trunion started to bend then the bearing caps simply got twisted out of the fork, bending the fork in the process. at the end the trunion snapped as the twisting continued.

I know I said I believe this was good enough for a lot of cars that may see high torque numbers (from looking at the applications list). Now having had a good look at the physical unit I have formed another opinion - I can see this being "good enough" for a automatic daily driver for your everyday joe, dick and harry. But it has no place in a manual or performance car.

So if these units are no good then where to from here?

I'm pretty sure I'm not going to put in these joints. I'm now looking at the E24 unit PN 26117518304, which is serviceable and available from BMW. It was also used in the earlier E34's. I'm going to order one and see if the dimensions are the same. If so then the next challenge is how to retain it. Cutting a snap ring groove is going to be a royal b1tch and I'll probably have to make up a jig on a miller. I could machine some covers/caps and tig / mig them in so not to burn the bearings but then I'll definitely have to rebalance the shaft unless I don't use any filler.

26117518304.jpg Picture from RealOEM, Looks just like the one I removed. Are the dimensions the same?

Or... I could place total trust and faith on modern technology and use hi-strength retaining compound and press fit them in...

Stay tuned!

UPDATE: Yes it will fit. looks like BMW haven't changed the dimensions of the U-joints for a very long time. Now I need to figure out an elegant way to stake these in. There are NO driveshaft shops in Hong Kong so I don't want to tack the caps and throw the balance off.... Some said because at least one end of the U-joints is "captured", either by the tranny yoke, centre bearing or the diff flange, a few tacks on the U-joint by itself isn't going to throw the shaft balance off...

[affa]

Finally got the E24 part 26117518304 and nope, its a bit small.... Some comparison pics with measurements:

DSC_0542.jpgDSC_0544.jpgDSC_0550.jpgDSC_0549.jpg

So the cap diameter is the same but the height/width is too small compared to the E31 OEM.
more to follow

[affa]

Looking at the GKN catalogue it looks like the 18725 has the perfect dimension, until you realise its bored through (picture lifted from another forum).

GKN18725.jpg18725.jpg

Its probably ok but I would like a solid U-Joint if I can find one (from OEM or decent manufacturer), so the search continues.

p.s. The 11754 (listed for a mazda) is only 3mm shorter (1.5mm on each side, might be the best bet).

[Mikekugel]

You might give these guys a call, http://www.driveshaftspecialist.com/...0html/BMW.html

[affa]

You might give these guys a call, http://www.driveshaftspecialist.com/...0html/BMW.html

If only the car was in the USA.... I wouldn't even bother doing it myself. I'm not being cheap, there is NO driveline shops in Hong Kong. Not one, nada, zip, zilch.

[sleepy81]

Looking at the GKN catalogue it looks like the 18725 has the perfect dimension, until you realise its bored through (picture lifted from another forum). Its probably ok but I would like a solid U-Joint if I can find one

Are you sure your's is not the same but with a capped centre hole?

[affa]

Are you sure your's is not the same but with a capped centre hole?

Totally solid! I could dunk it in water and check the displacement vs weight but it certainly feels solid in my hands.

[malcolmstevenso]

I am amidst the search for replacement U Joints for my 1991 850i base model Auto.
have found that the Mercedes Vito uses 24 x 74.5 mm U J but has hole in centre- also van was 116 HP so this not good enough.
Then I found FEBEST ASOP-ANT U Joint 24 x 74.5 mm This one is Solid in the centre of Cross - and is not drilled for grease nipple.
The existing yokes have 24.05 mm ID - so this perhaps decreases the press fit to hold them in place.
My plan was to make some button washers ecact fit above the U J bushings and TIG them in place with two spot welds.
Having said all this - perhaps better to save up and purchase a new Unit 26111226680, fiit it and forget it! owch

[rjjablo]

https://www.bimmerforums.com/forum/s...nt-Replacement

[Mike in CT]

Bought a rebuilt driveshaft from these folks for my 840 in 2009. Driveshafts.com Quite a few years ago.