Quill shaft trouble?

[bigstraight6]

My 2000 has quite an unpleasant resonance coming from the rear but only when coming off or on the throttle when at motorway speeds, it's fine when maintaining a constant speed it's only when backing off or reapplying throttle the the sound happens.

I thought it might be the exhaust where it passes through the subframe, but a good friend of mine who has owned big Triumphs himself thinks the problem is with the quill shaft. How could I check this and is it a simple enough job to rectify?

[tony]

Second the quill shaft theory. I had the housing break on mine some years ago after a similar vibration. Might pay to check the u/j's too.
Tony.

[David Withers]

I can't explain the science of it, but an out-of-balance rear wheel can cause vibration through the body when going into or off over-run at motorway speed. Might be worth checking for a lost balance weight before delving deeper.

[bigestate]

I would also check the rubber gearbox mount, when these collapse the metal part tends to sit on the crossmember which can also cause on/off noise vibes

[bigstraight6]

Thanks for the helpful replies so far, I forgot to mention there is also a droning bearing noise from the rear when at anything over 70 mph along with the resonance issues already mentioned, which I'm guessing could be the bearings in the quill shaft housing.

[johnconradlee]

I had that on mine recently (louder over 70 MPH and resonance issues) and was the gearbox mount (the quality of a certain suppliers gearbox mounts is dire - lasted less than a year!) and front propshaft UJ so I'd check that first, but then again could be the quill. If the gearbox mount has collapsed even slightly (on mine the metal-rubber bond had given up on the exhaust side but was still attached on the other side) tends to cause the front prop-shaft UJ to fail which causes even more vibration.
Does your diff leak from the front? - The gearbox oil leaks out of the nose seal and washes the grease out of the quill bearing. You should be able to feel play in it if it's gone.
I replaced my quill bearing last year. It's pretty easy to do but you have to take the back end of the car apart. I changed to another diff whilst I was at it. It is possible to do without removing the legs of the rear sub frame (I did this as was doing it on the cheap and didn't want to replace the sub-frame mounts) however it's a pain in the behind getting the diff back in.

[Clifford Pope]

I seem to remember it being possible to loosen the axle mounts at the rear and tilt it downwards at the front enough to be able to slide the quill housing clear. It needs the ends of the subframe lips grinding back about 1/4" as I recall to let the quill housing slide past.

[Mike Stevens]

In theory, the quill shaft bearing can be replaced with everything still on the car. You have to undo the prop flange (tight!), remove the outer circlip and then withdraw the bearing. That is the fun part I suspect.

I know my local Triumph garage many years ago used to do it this way to save all the dismantling.

I'm just replacing sun/planet wheel shims and also quill shaft stuff at present. With it all off the car that is!

Cheers,
Mike.

[Clifford Pope]

In theory, the quill shaft bearing can be replaced with everything still on the car. .

I did, some years ago, and it was quite straightforward.

What I can't remember is how much I had to grind off the flanges of the sub-frame arms, and whether simply loosening the rear diff mounts was sufficient or whether I actually dropped it. As they are rubber mushrooms in big holes I'd have thought merely loosening would allow the diff to angle downwards enough.

[Mike Stevens]

When I saw my local Triumph agent do it (I told you it was a long time ago), they didn't move the diff at all. They disconnected the prop, removed the flange, circlip and bearing with everything still on the car.

It's difficult to do the oil seal that way though!

Cheers,
Mike.