gearbox

[les]

I've just renewed the gearbox tailshaft oil seal. It still leaks! It seems to me that the seal used is too large in diameter to fit properly around the propshaft sleeve, hence letting oil by. I know this seal is rarely changed, but on the offchance that someone has done so recently, have they experienced the same problem? The associated parts are not worn, I could understand the leak remaining if they were. I suspect, as a pattern part, that the nearest size seal obtainable was used!
Anyone know the usual relationship between shaft and seal lip?

[chrisryder]

i fitted one about a year ago. i still get a drip every now and again but it's much better than it was before!

as an extra preventative measure we dribbled loctite around where the 'cap' sits on the tail casting to stop oil seeping through.

[bmcecosse]

The tail shaft bearing in the box may be worn - allowing the shaft to 'wobble'. And/or the u/j s in the shaft may be loose.

[les]

As I especially said---the associated parts are not worn.
Also the vehicle has not turned a wheel since renewing, it is just standing in the drive leaking oil (half a cupfull so far, in 2 days)
Must confess, not thought of it passing between the fittings.

[bmcecosse]

What was renewed? Tail shaft bearings have to be reamed after installation - was that done ? And if so - to what size ?

[les]

All ok and reamed to fit the prop sleeve.

[bmcecosse]

Well - unless you were given the wrong seal - or an 'old stock' item where the rubber has gone hard/shrunk -it really should hold the oil in. Perhaps not completely tight - but I would hope not more than an odd drip or two..........

[Declan_Burns]

The seal is usually a good fit. The yoke is 30mm (later cars) and the new seal is 29.2mm inner to the edge of the lip and has a spring so unlikely to leak there if reaming done correctly. It could be leaking from the sides. Are any grooves visible on the yoke-I had that issue after the propshaft was balanced and had to replace the yoke.
Regards
Declan

[les]

Thanks to all for your interest, I am now favouring the thought given by Chris regarding the interference fit between the tailshaft and the cap containing the seal. If there is any scoring or roughness in this area, it seems quite possible to cause a leak. With this in mind, I intend to stretch a section of rubber innertube (pushbike size) over the cap and tailshaft, if not a permanent fix, at least it should eliminate a suspected area.

[les]

To update the situation, I have backed off the prop yoke an inch or so and spotted a leak from between the aluminium gearbox tailpiece and the front end of the cap that holds the seal, (the area Chris applied his jointing). I have managed to stretch a 1 inch long piece of small innertube over this joint, and achieve an oiltight job. This may not be a permanant answer as not sure how well rubber will react with oil, but at least it proves a point. The metal to metal contact here has obviously some imperfections in the surface, letting oil by, and it is possibly the cause of many leaks from this area on Minors.

[bmcecosse]

Well done - good fix!

[les]

[chrisryder]

i presume that inner tube is thin enough to allow the prop flange bit to still clear sufficiently?

[les]

Yes Chris, it clears ok, and so far not a drip! Just hoping the oil has no adverse effect on the tube. On reflection I should have sealed it as you did.