Propshaft alignment

[paultv]

According to Bently, and common sense, basic prop alignment should have the universal joints on the same plane. Is this basically a truism for the E30 ??

I have an on going rumble problem that comes in at 40mph and vanishes at 55mph - I can feel it in the floor. This happened after a clutch/flexible coupling and centre bearing job done by Fritz and his Bitz.

My Prop U joints are NOT aligned in the same plane, but about 30 degrees different.



Paul

[pianist]

There are white dots on both halfs of prop that should be aligned iirc

[paultv]

I've found what looks like a white marker on the rear prop section, but the front has nothing anywhere, the car was so mutilated by the previous two owners - my only chance is to re position in one plane and then test it on the road.

Paul

[Motorhole]

White dots are painted on protruding dimples in my experience? Even if the paint has long gone, the dimples should still be there.

[paultv]

thanks for that - just pulling it all out!

Paul

[Brianmoooore]

Is this basically a truism for the E30 ??

It's a truism for any rotating shaft with universal joints. If a shaft, rotating at a constant speed, passes through a universal joint running at an angle, then the output shaft constantly accelerates and decelerates. Because of this, the second universal joint has to be in exactly the same plane, so that the output shaft from the second joint will be again turning at a constant speed, as long as the first shaft and third shaft are parallel.

[pianist]

Some deep words there Brian

Anyway I have checked my spare propshaft and when you align them two white dots the universal joints line up just like in your picture in the first post, hope that helps and it's probably what Brian meant with his jiba jaba too

[bigbird76]

Only 2 ways to fit the prop together

If you have no dots align as per drawing and try and if your still getting problems turn one half 180 degrees and try again , As per your diagram, Some props have small weights on them to balance also. If you have tried both ways and still have problems you might be able to take both sides to a prop shaft specialist to have a look for you. Also did you check that the centre bearing is pre loaded also?

Leigh

[Brianmoooore]

Only 2 ways to fit the prop together

If you have no dots align as per drawing and try and if your still getting problems turn one half 180 degrees and try again

This will work, as long as the two halves are a factory matched pair, and not from two different props.

[paultv]

Thanks for all the input guys,

Everything is fine except the UJ's were out by 20 degrees or so - I've found an original spot on the rear shaft and a nobble on the front UJ - I've re aligned everything now - so I guess it was incorrectly re-built at the Fritz shop as the car was really smooth before then (apart from squeaking centre bearing and clunky guibo)

Should have it all back together later today - fingers crossed!

Paul

[paultv]

What would excessive pre-load do? Bently says 4-6mm towards engine from natural rest position, what happens if it's more, does it simply reduce the life of the bearing rubbers?

Paul

[Brianmoooore]

does it simply reduce the life of the bearing rubbers?

That's what I would expect.

[paultv]

So.... after shelling out £1000 and 9 months of pretty miserable motoring, my cabby is quiet and smooth once more, thanks for all the help - no thanks to Fritz in Somerset for their poor workmanship and inability to fix the problem - I for one will give them a miss and would recommend everyone else does the same.

Paul

[Brianmoooore]

Mmmm! Interesting! I knew that Fritz's reputation wasn't that great, but this is something fundamental that even the doziest back street mechanic should have spotted instantly, or more exactly, shouldn't have assembled wrongly in the first place.