S2Bray

... and not drive shaft cup wear - they've been swapped in an effort to rid me of this vibration.

Most noticeable between around 4-5000rpm, under load; either hard acceleration or increased effort going up hills. If I knock it out of gear of back off, the vibration stops/eases

I'm inclined to think for that reason, and that I have 2 sets of wheels and the symptoms are consistent, that its not out of balance wheels.

It definitely feels like it comes from the rear.

Any thoughts?

johnckeen

diff...? maybe mounts are shagged?

S2Bray

Don't suppose you know how to inspect/what to look for to assess diff mounts?

har-vey

There rubber mounts so check for cracks or splits

nomadicS2k

I would check for excessive movement on the diff - this is possibly the less likely option - the more likely option is the rear drive shaft joints need checking and have work (although still I would expect this at all rpm's)

Couple of bits of reading:
Link 1
Link 2

S2Bray

Thanks for the comments.

With regards to diff mounts - when jacking up the rear of the car (on the diff), how much movement/slack would you expect the diff to take up before lifting the car. I reckon mine moves maybe 10mm before it 'bottoms out' and lifts the car. If this is excessive, I reckon I may have found the culprit!

Winstan

When i jack my car up from the diff there is no noticable play. Definitely not 10mm before lift, looks like you found your culprit. If not i would say its beneficial to replace the mounts regardless.

S2Bray

Thanks mate. This is good news! ...sort of.

miloking

ahhh i see you already swaped cups... did you just swap them left to right or got some new ones?

S2Bray

Swapped left to right. They weren't noticeably warn though. Which perhaps isn't all that surprising given it didn't fix the problem.