Replacing gearbox seal

[Rubce]

Hi All

Can any of you give me some advice on how to replace the front and rear oil seal on our gearbox. It's a 4 speed with a D type overdrive fitted.

Thanks in anticipation.

Bruce

[Anthony]

And whilst we're at it, what other items shoul be checked and/or replaced?

[Nick Jones]

Rear oil seal is possible (just) with the box in the car, but much easier with it out.  Front oil seal definitely not.

Rear oil seal:
You'll need to find a way to lock the output flange so you can undo the nut.  Couple of suitable bolts through two of the flange holes and then a bar through those is the quick and dirty method.    Remove locking split-pin (if fitted) and undo the flange nut.  Flange should then pull off.  Might need a bit of gentle encouragement with a soft-faced hammer.

You can then dig/lever the old oil seal out taking care not to damage the housing or shaft.  New one is then tapped in evenly, flush with the housing.  Spring/lip faces into the gearbox.

Check the flange you removed to see if a significant groove has been worn where the seal lip runs.  If so, you may want to tap the seal a bit further into the housing so the seal lip runs on a new area.

Refit flange with a new nyloc (threadlock or split-pin) as applicable and torque up.

Front oil seal:
You have to remove the bell housing to get at this so will also need a new gasket.  Be aware that some gearboxes don't even have a front oil seal but have a scroll arrangement instead.  I'm not sure if it's possible to tell which is fitted without dismantling.  I'm also not sure whether the scroll type was ever fitted on the GT6 'boxes.  I suspect not as I've never seen one on a 6 cylinder (or Dolly 1850) box.

Remove clutch forth an release bearing carrier.  Undo bellhousing bolts noting that the centre ones have (or should have) copper sealing washers.  Remove bell housing watching for three small springs that may fall out.  These are not present in all cases but are used to put some pre-load on the front layshaft thrust washer.

Dig out old seal and tap new one in using a suitably sized tube or socket as a drift.

Clean up mating faces and reassemble with new gasket and Blue Hylomar (or similar).  It's a very good idea to wrap the splines of the gearbox input shaft with a smooth tape before passing the new seal over it to minimise the risk of damaging the new seal lip.  Apply a little grease to the seal lip/input shaft.

Refit bolts not forgetting the positions of the ones with the copper washers! New copper washers would be ideal.....

Nick

[Rubce]

Hi Nick

You are a star providing such a detailed response :). The engine and gearbox are currently seperated and out of the car so access is not an issue.

Regards

Bruce