Rear Diff and Gearbox oils and drainage

[Skelly65]

New to all this any ideas on best oil to use on rear diff and gerabox and whats best way of ensuring they are drained correctly and how on earth do you fill the rear diff? (think I have a rear diff leak will this just be a gasket?)

[RobMoore]

I'm also interested in diff oil change, owners manual states filled via a point in the rear floorpan under seats but mine are solid with no circular cover plate.

[alanworland]

I have the cover under the rear seat, but I always fill the axle from underneath!
If you go under the car (not jacked) from the rear it can be filled quite easily with one of those bottles with the flexi pull out piece.
Oli leak could be the gasket (half shafts have to come out to release the diff) or it could be the pinion seal (prop shaft rear end dropped and flange from diff removed for access to seal) or, if leaking into brake drums half shaft out and hub /bearing removed for access to seal)
Manual will specify oils - axle hypoid 90, gearnox probably engine but mines hypoid 90 (sidevalve)
Check manual for both, you need to get this right!

[PSL184]

Cars that are pre 1098 engine had the filler on the diff itself which was accessed through a plate in the rear floor. 1098 cars had the filler on the axle casing which is accessed from the rear underneath the car. Hypoid EP80 or 90 gear oil for the diff and 20/50 or 10/40 ENGINE oil for the gearbox....

[bmcecosse]

Best to drain them after a good hard run - to make them flow easily. The 10W 40 oil in the box will cause less friction drag. Only use 20W50 if the box is a bit 'worn'.