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Transmission vibration @ 60mph


Snagger

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My late RRC has a thrumming vibration that appears at 58mph and continues all the way to 70. It's most evident when accelerating. The suspension bushes, prop UJs, CV joints, wheel bearings and brake discs (vented) have all been replaced with no effect, and the wheels have been re-shod and balanced. there doesn't appear to be any play in the transfer box or diff pinion bearings or the prop shaft's slip joint. Does anyone have any ideas on what could be causing it?

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I'd check the viscous couple ing is working okay.. Does it scrub excessively when performing tight turns? If you jack up one wheel with the main box in neutral, handbrake off (Other wheels chocked obviously), can you rotate the wheel by hand?

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No, not by hand, but I had the coupling checked by Rogers of Bedford a while ago and they said it was fine - I watched them get some differential movement with pry bars through the prop yolks nearest the transfer box while it was on the ramp. It looked awfully stiff to me, having expected it to be relatively free until any slip occurred, but they said it was normal. The front tyres do occasionally squeal slightly on smooth concrete in multi-storey car parks or greasy tarmac when at full lock.

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Sounds like you have checked all the usual items so this could leave gearbox mounts, or engine mounts as potential candidates - under acceleration the engine/gearbox assembly will try to flex due to the load and if their is any looseness it might be resulting in the propshaft/s vibrating>?

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There is no vibration through the steering wheel. The vibration is very small in amplitude, and is only minor through the seats and floor; it's more of an audible problem.

Damper bushes have been suggested elswhere, as has the harmonic damper. They appear to be fine, though I'm not quite sure what to check on the harmonic damper - there doesn't seem much to check.

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  • 2 years later...

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