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Rear End Violently Shaking/bouncing?

skybt1
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skybt1 Community Regular

skybt1

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I have a problem with my rear end violently shaking under full power when accelerating.

It feels like axle tramp but its real violent. Ive been told its not axle tramp because its irs

but thats what it feels like, and it is bloody terrible.

It feels like the rear wheels bouncing up and down real quick real violently.

Is it my rear suspension set up?

Is it my diff?

What is it? It only happens in the 1st and 2nd under full acceleration.

car is mr30 sedan, man with an R200 viscous lsd.

Anyone help or had the same problem?

My gut feeling says its the suspension...

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Factory 5 Mentor

Factory 5

Posted
Posted

when i had a VL turbo wagon, the bearings in the gearbox were worn causing vibration in 1st and second under heavy load.

also the rear wheel bearings needed replaceing , so these 2 things could add up.

the mechanic says it was all caused by a un-balanced tailshaft...

skybt1 Community Regular

skybt1

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  • Author
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Thats one thing i havent taken into consideration purely for the fact that this car has seen 4 tail shafts, from stock

to modifying it over the years for different gearbox and diff and the one time it broke the rear uni. I didnt think that

all 4 tailshafts could be out of balance, especially with the last one being bran new.

Ive been having this problem ever since i chopped the rear springs years ago. Since then ive changed the tailshaft

3 times and rear suspension 3 times. The only thing i have not changed yet are the rear wheel bearings. I thought

that these only get changed when they are noisy?

I just thought it was the use of crappy springs in the back that are too soft and have a bad rebound quality or something

along those lines.

Its just real annoying, sounds scary in the car and i know it's not right and needs to be fixed :)

blind_elk Grand Master

blind_elk

Posted
Posted

How to prevent axle tramp? Well, how about - "stop dumping the clutch"?

But generally, axle tramp is caused by the shocks and springs being totally mismatched. So, yes, it's a suspension thing.

skybt1 Community Regular

skybt1

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when i dump the clutch it just fries the tyres. It happens more when i ride the clutch into power then release it.

Then when i snap second and squats down it does it again. Then into third it disappears due to rolling speed and lack of power. It doesnt squat as hard in third. So thats why i was tending to a suspension problem.

Any recommendations for a good rear suspension set up?

Matty T Collaborator

Matty T

Posted
Posted (edited)
It happens more when i ride the clutch into power then release it.

Then when i snap second and squats down it does it again. Then into third it disappears due to rolling speed and lack of power. It doesnt squat as hard in third.

A-ha! From what you describe, I am 99.99% sure that the problem is the clutch. There is oil on the clutch plate. This causes the clutch to "grab" rather than slip, and results in a "shudder" in the driveline. Been there, had that.

You are going to need to pull the box out, replace the clutch (the clutch plate is fooked now), clean the flywheel (if not have it machined), and put the lot back together.

Edited by Matty T
skybt1 Community Regular

skybt1

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serious? i would of never thought that!!! why on earth would there be oil on my clutch????

does make sense though. at least now im glad its not the rear suspension. that would explain a lot. its also one of the

things i have not changed!!! ive changed diffs, tail shafts, cv shafts, suspension the works! looks like the clutch is next!

thanks for your diagnostics and help.

Matty T Collaborator

Matty T

Posted
Posted

All it takes is a leak from either the rear main engine seal (common) or from the gearbox input shaft. With a bit of bad luck, oil can get sprayed onto the flywheel, then to the clutch plate.

The other possibility is that either the clutch plate has dropped one or more springs, or the pressure plate has started to fail. Whichever problem it is, I am pretty sure that your issues are clutch related.

Matty T Collaborator

Matty T

Posted
Posted
I didnt realise oil could cause so much trouble. I would have thought that it would just burn away.

That is also why you need to make sure your hands are clean when you handle the clutch and pressure plate. You don't want to transfer any oil onto the surfaces.

Replace the seals if they are leaking, yes.

skybt1 Community Regular

skybt1

Posted
  • Author
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Before you do get a new clutch, have you checked all the mounting points and rubbers for the diff?

None of the rubbers are torn on the moustache bar. Should there be rubbers between the diff and the rear cradle?

For memory the four holes that are bolted to the rear cradle have no rubbers, just nuts and bolts. But i had the same

problem with my old diff too.. Its very odd.

  • 2 months later...
skybt1 Community Regular

skybt1

Posted
  • Author
Posted
All it takes is a leak from either the rear main engine seal (common) or from the gearbox input shaft. With a bit of bad luck, oil can get sprayed onto the flywheel, then to the clutch plate.

The other possibility is that either the clutch plate has dropped one or more springs, or the pressure plate has started to fail. Whichever problem it is, I am pretty sure that your issues are clutch related.

I just wanna say thank you for your diagnosis. You were spot on! Just got around to finally changing the clutch and it has cured all my haunting troubles. Thank you!!

cazz Rising Star

cazz

Posted
Posted

You may also want to inspect and check your rear engine mount. Even if it doesn't look like it has cracks in it, it may be very soft, and causing driveline vibration on take off. Rear engine mount actually hold the gearbox up, in case you haev trouble finding it.

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