Rear End Violently Shaking/bouncing?

[skybt1]

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...

[skybt1]

no one must of ever had this problem before..i was hopin i wasnt the only one!

[the big JC]

no one must of ever had this problem before..i was hopin i wasnt the only one!

ok wat it sounds like to me is an out of balance tail shaft

[Factory 5]

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]

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

[Matty T]

Get a mate with a video camera to video the rear wheels (both sides) while you accelerate up the road. If it is rear wheel hop, you should see it on the video.

If it isn't, I'd be looking at the halfshafts and diff centre.

[skybt1]

that sounds like a plan.

If it is real wheel hop, how do would i go about fixing it?

Is it a suspension thing? Bushes? Springs? Shocks? What causes the hop to happen most??

[blind_elk]

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]

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]

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 June 17, 2007 by Matty T

[skybt1]

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]

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.

[skybt1]

so while im there i should be looking at changing the rear main and input shaft seal??

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

[Matty T]

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]

Any clutch recommendations? Will be on an RB30ET. I was lookin at getting an eXtreme clutch. They any good?

Looking at handling around 350hp.

[blind_elk]

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

[skybt1]

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.

[skybt1]

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!!

[Matty T]

You are most welcome. Glad to be of assistance!

[cazz]

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.