Prop Shaft Question

Rek

Rek

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There is a splined section on the front part which fits into a female part of the rear shaft. Behind a cap are seals but nothing physical to hold the splines in place laterally. Is it the case that these splines move in and out during normal operation and if so what condition does it solve?

Mine was very stiff and still is. I have suffered from prop slap during high torque acceleration in 1st and 2nd and thought that it might be the engine movement. There are at least two other members with this issue which I initially thought might have been excess engine movement.

I took videos of the acceleration using a GoPro and the engine does not move that much however the centre of the propshaft spins but gets into a wider oscillation from centre under heavy torque. I found a BMW engineer on a group ( Yeah, I know) who said that this might be caused by UJ's binding moving the angle of the prop shaft.

So, do these plines have to move and if so why, and by how much?
 
once installed to proper length, the nut is tightened and the splines do not move.
the nut seals the splines.
IMG_2060.png
 
I would look at motor and transmission mounts based on your description.
 
It’s either a u-joint or center bearing I would guess..
Inspect and post a pic of center bearing
After that pull drive shaft and feel for bad joints.
 
I have the video of the movement and it does not appear to be engine or gearbox mounts. They are all fresh and whilst there is some movement I don't think its enough to cause the oscillation of the middle of the prop shaft. If I can edit the size of the videos down I will post them so peolle can take a look.

The UJ's are may be the culprit, or perhaps the balancing, but the UJ's were replaced when the 5 speed was fitted in 2020 and there has only been moderate mileage since then.

The prop shaft is being removed and will be inspected and rectified if deficient.
 
Rek, take the prop to JW Engineering in Bexleyheath, Dartford. I had no hassles with them whatsoever, many friends that took theirs elsewhere and had issues.
I highly recommend JW Eng and know professional mechanics that use them frequently.
They did mine inc, UJs, centre bearing, balance and paint, sensible price but better still, everything just worked right first time, on time.
 
Rek, in the diagram above there is part 13, it's a splined rubber type material bush that's clamps the two spines. Earlier cars, e9 etc are coarse spine, generally later cars from e28 are fine. I have search for months high and low for a coarse spine bush but cannot find one. I used a new one out of a spare prop for my race car to install in a friends restored e12 m535i....then to discover I couldn't find a replacement. Be aware, if you use the part number for the correct coarse one, you will be sent a fine spline one. I now have 6-7 of the wrong one, even from BMW themselves. If anyone does have a source (and not just a webite with the correct picture and part number because the one that you will likely be sent is the fine type) that knows for sure they have the correct one it would be very welcomed.
 
Rek, recently experienced a number of prop issues on a large number of e12, e28 alpina/M car props. Worn male/female spines, retubed in wrong wall thickness, something dragging on the prop to cause annular depression, balance out, excessive play in UJ's, damaged nose end (the part that protrudes out of the front). In short scrapped maybe 50% of the props, not economic to repair.
 
I threw away every used driveshaft in my shop.
Nothing but huge trouble.
 
sfdon said:
once installed to proper length, the nut is tightened and the splines do not move.
the nut seals the splines.View attachment 185891
Click to expand...
I thought this was the case but the splines do move and the nut or cap merely keeps the dust seals in place. Something a whole lot beefier would be required to fix the splines. The movement will be slight but it will take up any change in distance from the rear diff on its mounts or the gear box on its mounts. I would guess thats why the splines are there in the first place.
 
The prop has been taken off. One of the UJ's is Ok to the point of just moving and the other one (diff end) is binding badly. They were meant to have both been replaced when the 5 speed was fitted. They may have been faulty UJ's but this would have been apparent once fitted, as the oscilaltion happened immediately they were fitted, so no logical reason why they are the way they are. Either way, it's off to JW for testing, full balancing and replacement UJ's again.
 
Rek said:
The prop has been taken off. One of the UJ's is Ok to the point of just moving and the other one (diff end) is binding badly. They were meant to have both been replaced when the 5 speed was fitted. They may have been faulty UJ's but this would have been apparent once fitted, as the oscilaltion happened immediately they were fitted, so no logical reason why they are the way they are. Either way, it's off to JW for testing, full balancing and replacement UJ's again.
Click to expand...
Sounds like you have found the issue, JW Eng will sort it for you I’m sure. Enjoy the smoke!!
 
The work has resolved the issue fully. The prop was slightly short by 17mm so was lengthened so that more of the splined section was inserted into the female section. The UJ's were badly worn despite me being charged for there replacement when the 5 speed box was fitted (prop adjusted at the same time). There is now no sloppiness nor tramping within the bearing carrier. Anyone in the UK should know that this was down to the detective work of Bill Russell who looks after two members car here and whom I can thoroughly recommend.
 
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