Help - rear wheel locking when reversing

[Aidan]

the wheel lock you are describing must be either due to reverse idler and reverse gear locking instead of running normally, but they spin together all the time just not locked to the shaft so that's unlikely unless mainshaft bearing has failed/is failing, or the pinion head and crown wheel meshing in such a way that they lock instead of happily push each tooth along, I couldn't say if it would do that in forward, perhaps on the overrun which is similar forces to reverse, is it noisier on the overun ?

[vwhobo]

Sorry, not familiar with terminology - what's 'the overrun'?

[Aidan]

when you lift off the accelerator completely and the vehicles momentum is driving the engine or if you use heavy engine braking on the way down the box

[vwhobo]

OK, got that - thanks. When I lift off accelerator, nearly all gearbox/diff noise disappears. Hardly ever use engine breaking by changing gear - but within a gear going downhill - again, foot off accelerator, noise goes.

[Aidan]

Pinion bearing is very worn and pinion head is moving under load from it's correct no noise position to the whiney position. Because the diff can't move the pinion is driven forward by the load when in drive. But the crown wheel and pinion can eat into each other over time, oil change will minimise wear by providing good lube but will also clean out further dirt and debris from inside the case which becomes suspended in oil reducing it's lubeness, only postponing the rebuild work.
Dave Pickles has got a cheap enough used 5 speed up for sale....

[Rozzo]

wow aiden i'd heard your reputation but you really are a god of gearboxes

[vwhobo]

Once again, thanks for all your help Aidan. Guess I've got some decisions to make!