a grumbling whine type noise is comming from the gear box when in gear driving or with the clutch up in neutral! Disappears when the clutch is depressed. I’m thinking it’s main bareing . What do you guys think? Any ideas and is it had to fix. Gear oil seems to be ok but probably is quite old!
Gear oil seems to be ok? How do you know? Drain it fully and refill using GL4 gear oil, Castrol is good, so is Castrol Syntrans.
undo the top up plug first before the drain plug....dont want to drain and then find top up plug seized up! My old drained out oil smelt like cats wee, and what a difference fresh oil made.
Very likely main bearing as thats what normally goes first (also mainshaft and bearing is driven when in neutral - as you correctly deducted) . I have rebuilt gearbox for sale or can have a look at yours if you want.
How big a job is it to replace the main bearing? I assume engine out but do you need to remove the gearbox also?
Unfortunately its full stripdown so you might as well rebuild it at the same time. So yes gearbox out.
