Differential oil 'leak'?

[david muir]

Hi, Just had the car ('64 3.8 ) mot'd. Examiner informed me of an oil leak at back axle. Car was still on ramp for me to have a look- coating of oil mainly at front area of diff., anti-roll bar covered end to end. No sign of oil at discs i.e. output seals and no evidence of oil at propshaft-end seal. Only thing I can think of is that the breather has blown oil out after a recent track evening. Can't remember what the breather arrangement is(no pictures in Haynes manual)- anybody had a similar experience? What's the competition set-up?
David

PS car passed MOT!

[Heuer]

Could be:

1) diff over filled
2) baffle plate missing in diff cover

On the other hand the breather is at the rear so I would expect the oil to be from there back, not forwards. Have you checked the oil level? Only other thought is the oil is coming out of the gearbox or engine and being carried backwards by air flow. Case of checking levels in the box and engine as well.

[johnney]

Are you sure its oil and not brake fluid?

[abowie]

If it's oil I be it's coming from further forward; GB rear seal or engine.

[david muir]

Definitely oil. Recently had the speedo cable off to lubricate, will check if it's the speedo gearbox seal( and check the gearbox oil level).

[Heuer]

Very easy to loose the 'O' ring seal on the speedo cable end where it goes into the speedo gear housing. There should also be an O ring on the gearbox shaft where it goes into the main box.

[david muir]

Hi, Changed gearbox oil and measured old volume-about 1/2 US pint missing.(3 US pints is full) Went out for a thrash and would say that it has leaked more! Oil is travelling from gearbox rear are along underbody rails to rear.
David, was your gearbox leak, from speedo gearbox assy., travelling rearwards along the rail on the offside of the car?
Will have to remove all the interior gearbox cover etc to check the speedo gearbox area properly (and probably drive the car with it all out.)

[Heuer]

My leak came from four 'possible' places - speedo gearbox, top cover gasket, rear seal and selector O ring. I took the car over to Paul Brown in Ripley and he put his video bore-scope in there to have a look around Unfortunately there was a fair bit of oil splashed around so difficult to figure out where is was coming from but we all prayed it was not from the rear seal. When I got home I checked the PO's invoices and found the rear seal had been replaced as part of the restoration so I decided to work on the other suspects. I removed the gearbox top cover and found the gasket was a soggy mess. In addition the O ring on the selector shaft had clearly never been replaced and oil was sneaking past. Both were replaced and I took the opportunity to clean and overhaul the gear stick bearings with new Tufnol washers and rubber bushes. Finally I got the speedo box off (you need to remove the rear gear box mount first so you can lever the engine/box sideways) and found the O ring between box and cable was missing. It is very easy to put one on and have it drop off without you noticing when putting it back so care is needed. Finally I filled the box with Red Line MTL which transforms the synchro action of the Moss box - essential for your driving enjoyment I would say. So far the box is leak free.

If you still have a leak after these easy bits of work then it must be the rear seal which is either an engine out job or with patience, time, skinned knuckles and a bit of transmission dismantling can be done in situ.