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Juddering in reverse gear - GT6


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Fresh from it's restoration, my car is driving very well with no vibration, but I notice that in reverse, it is hard to move without what feels like the prop shaft (but I have no idea) 'juddering'. It's quite bad, a bit like the problem you sometimes get with a clutch when pulling away in 1st gear (when something is wrong I mean!)

As I say it feels like the drive train somewhere, certainly not Engine. 

I vaguely remember that it was doing this before I took it off the road 20 years ago.  Prop, gearbox, diff are untouched in the restoration.  Everything else new (inc clutch & rotoflex of course)

Hoping someone may recognise the fault?

Thank you!

Rich

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I used to have this symptom with my Vitesse. The problem has disappeared after swapping to CV driveshafts. I've wondered if it might be the Rotoflex couplings reacting to the torque as the rear of the car lifts slightly in reverse, rather than squatting down in forward gear?

 

 

 

 

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13 minutes ago, rulloyd said:

Thanks Johny.  Would that happen just in reverse?

Definitely worth checking. It might be worth getting the car up on secure stands and viewing the drive train while an assistant runs the engine and operates the gears...

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10 hours ago, johny said:

Definitely worth checking. It might be worth getting the car up on secure stands and viewing the drive train while an assistant runs the engine and operates the gears...

You might find that without the loading on the wheels and suspension, that the issue would not replicate?.

I recently bought a Peugeot 107, the semi auto, It has a tendancy to "wind up" on take off if you are too heavy on the throttle. Replacing the Engine mounts had (almost) cured that. But on the Axle stands it would not replicate?.

Pete

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It's possible that one of the propshaft UJs is worn or that a tooth is damaged on the reverse idler, but check johny's suggestion first! It's probably worth a quick "check for play" while jacked up - put it in gear with engine off and see how much you can turn the diff input flange by hand. There will be a little play but it shouldn't be masses.

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there are so many culprits in this problem 

bent rear engine plate

clutch cover  drive straps 

gearbox mounts

engine mounts

clutch damper springs 

diff mounts 

tie rod /trunion bushing

prop UJ

prop telescope 

and so on can be one or many   this is where you need to be careful or chasing your tail can become expensive 

Pete

 

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1 hour ago, johny said:

Unusual to only do it in reverse though?

So what is different in reverse?. The only thing I can think of is that the rear axle alignment is moving. Going forward the thrust would vectored in compression onto the Rear outrigger. So going astern, the strains would then be tensile. One would assume that with all the fasteners tight and bushes in good order nothing would/should change more than a few mm?. The tendancy to "squat" when torque is applied to the rear going forward, would be reversed going astern. The rear spring fastening is not "slack" is it? or even a cracked leaf?.

Pete

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