Replacing rear gearbox oil seal through a 4 inch hole

[david.g.chapman]

I have just replaced the rear gearbox oil seal on my 4 speed plus 2, with the engine and gearbox in place.

I though it would be a good idea to post this, in case anyone else is crazy enough to try it Note that the bush in the gearbox rear end should be in good condition otherwise the new seal will not last long.

1. Raise car evenly 18 inches or so on 4 stands.
2. Unbolt the propshaft and pull it backward out of the gearbox - there are some excellent posts on how to do this.
3.Take out the driver's seat, remove the center console and the rubber plug, and peer through the hole. The end of the gearbox should be towards the right hand side of the hole - if not, I don't think the seal can be changed.
4. The old seal needs to be removed. Place an old heavy flat screwdriver (or similar drift) on the metal shoulder of the seal nearest you. Again, if the seal is too deep and there is no shoulder, I think it's game over. Use a club hammer and bend the seal inwards to collapse it away from the gearbox casing. You will need to move the screwdriver up and down 30 degrees or so and drive in again. Once you see a gap, reposition the screwdriver to the back lip of the seal inside the metal flange, and lever it out.
5. Get a new seal. The seal has to be the type with a metal cylinder on the outside, not rubber.
6. The seal as it stands is too big to drive into the gearbox through that 4 inch hole. The interference is too great. I reduced the outside diameter of my seal from 43.8 to 43.4mm (yours might be different) by filing carefully and evenly around it in a vice with a socket clamped against it. The loss in concentricity will be very small (less then 0.1mm) if you are careful. I think this is OK for the seal but correct me if I am wrong. Use a digital caliper and keep checking. Try not to get any flats, although small ones can be sealed later. Keep trying the seal in the gearbox hole the wrong way around until you feel it "thinking about" going in. The diameter of the seal is slightly less at that end.
7. Smooth off the surface of the seal with emery paper.
8. Clean the seal and the gearbox casing with meths and a Q-tip.
9. Coat the seal and the casing surface thinly with oil resistant RTV (I used JB weld black).
10. Warm the geabox end with a hot air gun.
11. Use a small hammer and tap the seal into the gearbox to leave a slight shoulder showing for next time. Mine just tapped in. If the seal is going in in too easily it might spin later on. The RTV will help but I would play safe. Stop, yank the seal out, buy another one and try again.
12. Go and have a cuppa.

Good luck if you want to try it!

Dave Chapman.

[nomad]

Dave, I just did this job on Midget. Very little access as well and I used the drive shaft to drive the seal home. Put a piece of thick walled tubing over the OD of the drive shaft yoke to do the job. Not sure if an Elan would allow it but might be worth investigating.

Kurt

[david.g.chapman]

Yes, Nomad - that's not a bad idea. A propshaft slide hammer!

You could get away with a greater interference fit as well as you have more power- although I am not sure if the unmodified seal could be used.

I think someone whould have to hold the spacer through the hole to clear the rubber internal lip on the seal. The spacer would then engage on the metal shoulder. Another person working under the car would then pump the propshaft.Watch your fingers!

Dave.