Rear Gearbox seal

Post by **weets** » Tue Jan 30, 2007 8:32 am

Help please, my gearbox ( MM1098 ) is leaking oil were the driveshaft exits.
So I presume that the seal needs replacing.
It looks to be a felt pad?
How do you remove the cover to replace the seal.

Hope someone can help.

Post by **bmcecosse** » Tue Jan 30, 2007 10:07 am

The leak may be caused by undue wear on the universal couplings in the prop shaft - check them carefully. I believe the seal just knocks off the end of the gearbox - and a new one presses on. It's a job i have never had to do ! Someone who has done the job will be along in a minute. I'm sure.

Post by **chickenjohn** » Tue Jan 30, 2007 11:09 am

I've done this job and I'd love to know the proper way of doing it with the best tool for the job. I resorted to cutting the metal lip of the seal and chiselling it off. The new one I tapped it into place with a rubber mallet.

The metal lip of the seal fits into a groove in the gearbox housing by the rear driveshaft splines.

Post by **rayofleamington** » Tue Jan 30, 2007 5:06 pm

Underneath the felt washer (dust guard) there is a lip seal. This is all part of one assembly inside the steel cap. This can be removed but first you need to 'un-crimp' the end furthest away from the felt washer. you can either do this by sawing into the steel case and lifting it up or by filing/grinding the crimped parts away.
When you've undone the crimp, it can be tapped off and replaced. Replacing the seal is the easy part, so hopefully that is all that needs fixing...

Please bear in mind that the propshaft sits in the back end of the gearbox in a plain bush (a bronze plain-bearing). This bush can get worn away with high mileage or if the gearbox oil is low. If the propshaft is loose in the bush (you will feel side play) then the bush needs to be replaced. It is eassy to check by seeing if you can move the prop around when it is installed into the gearbox - if there is play you will feel it.

The new bush needs to be machined to size after fitting (try an engine machinist or decent tool room - this can be done using an adjustable reamer).

If the bush is very badly worn, then the propshaft can run-out. This is often part of the cause of a leaky seal (unless the seal is just heavily worn). Significant run-out will damage the gearbox if left unfixed.

If there has been a lot of play in the bush, then it is also best to scrap the propshaft in case the propshaft nose has worn eccentric.