Prop Shaft/Hand Brake Collision

[philcreed]

I have a Sportster with a BMW 3.2 litre M Power engine and all BMW running gear. It was built for me by Marlin and delivered in 2007. During that period it has only covered 2500 miles.

The problem I have is when I accelerate rapidly from start or in second gear the prop shaft is hitting the hand brake cable guides. It must have been like this from the very start but went un-noticed as I was "gentle" on the accelerator in the early days.

the question is, can I adjust the rear suspension to create the clearance that will avoid the collision between the prop shaft and the hand brake tunnel guide or is the solution more drastic. Drastic, being to cut through the prop shaft tunnel and raise the hand brake cable guide sufficiently to obtain the required clearance.

Any advice will be greatly appreciated.

Thanks,

Phil Creed

[greatoldone]

Re: Prop Shaft/Hand Brake Collision

Hi Phil,

Is there anyway you can get some photos of the current setup? It will help any troubleshooting.

I'm guessing that your car will be an E36 based Sportster, given what the engine. So the rear-end setup will be different to my E30 based one - that said, I wouldn't have thought that changing the rear suspension would give you extra clearance, as the diff is fixed in place. Dropping the diff down slightly might help. How you'd achieve that though... I don't know, without looking.

Cheers

Jason

[cameronfurnival]

Re: Prop Shaft/Hand Brake Collision

Would it be worth checking the engine, gearbox and axle mounts too as they might be causing too much movement?

[philcreed]

Re: Prop Shaft/Hand Brake Collision

Hi Phil, Is there anyway you can get some photos of the current setup? It will help any troubleshooting. I'm guessing that your car will be an E36 based Sportster, given what the engine. So the rear-end setup will be different to my E30 based one - that said, I wouldn't have thought that changing the rear suspension would give you extra clearance, as the diff is fixed in place. Dropping the diff down slightly might help. How you'd achieve that though... I don't know, without looking. Cheers Jason

Thanks for your interest Jason.

Can't do anything about photos tomorrow by I'll try and post some on Friday.

Cheers,

Phil

[nigel]

Re: Prop Shaft/Hand Brake Collision

Hi Phil.

Very, Very Interesting......................

I have an E36 based Sportster (M50B25 engine). I bought the kit in 2010 so I'm not sure whether a 2007 model would be E30 or E36 based. The rear suspension set ups are quite different.

But if I accelerate hard in first or second gear (or hit a bump while accelerating in 3rd) I get a noise that sounds like a machine gun from somewhere around the centre of the rear bulkhead. My first thought was that it was the prop shaft whipping and hitting something but I have looked closely underneath the car a number of times but can't see any witness marks, either on the chassis or the prop shaft.

But I don't actually remember looking closely at the hand brake cable guides. Ill check it out this weekend.

I have always been suspicious about my diff carrier bushes and wondered if they are on their way out, allowing the diff to rotate (upwards at the front) under hard acceleration. That would certainly allow the prop shaft flange to make contact with the guides even if there is plenty of clearance under 'no drive' conditions. Alternatively, the dodgy bushes may be allowing the diff carrier to rattle between the upper and lower front diff carrier mounts which would create a similar noise.

Thanks Phil. You've given me something else to investigate. I'll let you know how I get on.

Nigel

[philcreed]

Re: Prop Shaft/Hand Brake Collision

Hi Nigel,

Your problem seems to the same one that I have. My running gear came from a Z3 that had 49k on the clock. Can't think it would be the diff carrier bushes but you never know. I would be interested to what you find out over the weekend.

Regards,

Phil

[greatoldone]

Re: Prop Shaft/Hand Brake Collision

I seem to recall someone had issues with the propshaft flange being to large at the gearbox end, meaning it was rubbing on the gear selector. He ended up having the flange turned down to a more appropriate outside diameter. Could you be suffering the same thing at the other end? If so, taking it to a prop specialist having it re-sized might be an easier and less drastic solution.

Cheers

Jason

[philcreed]

Re: Prop Shaft/Hand Brake Collision

I seem to recall someone had issues with the propshaft flange being to large at the gearbox end, meaning it was rubbing on the gear selector. He ended up having the flange turned down to a more appropriate outside diameter. Could you be suffering the same thing at the other end? If so, taking it to a prop specialist having it re-sized might be an easier and less drastic solution.

Cheers

Jason

Thanks for your thoughts Jason.

I considered that pretty early on. The thing is I reckon I want 10mm to be sure. 6mm may be sufficient but I only want to do it once. I don't think I could machine 10mm off the flange. Nevertheless I will check it out and let you know.

Cheers

Phil