Gearbox shift shaft seal

Drops of oil on your driveway or garage floor in the centre of the car ? A little mucky in the small window that peeks into the back end of the gearbox ?

The gearbox shift shaft which connects onto the gearshift lower shift rod, runs through a round seal which plugs into the end of the gearbox. This seal has a habit of wearing or going soft and it also contains a little spring which can cause it to leak as well.

This is a quick and easy job but annoying if you don't have a lift or inspection pit.



13mm socket
10mm socket
Ratchet + extensions
phillips screwdriver
blue thread lock
degreaser + rags for cleanup

Don't worry about the mess too much. A small bit of oil makes a big big mess. I once spat out some gearbox oil at brands hatch from the box breather and looking at the underside of the car in the pits it was like i'd lost about 10 litres but in reality i'd only dropped a few tablespoons worth.



Ideally get the car up high onto 4 axle stands (unlike my picture !). Remove the protection cover just forward of the transmission undertray. This needs 4 plastic 10mm trim nuts undoing and then 3 phillips screws on either side around the jack points.



Here you see everything exposed. The rubber boot is soaked in oil.

Pull back the rubber boot and you will see the bolt that secures the end of the gearbox shifting rod onto the stub of the shift shaft.

Undo this bolt with a 13mm socket. You will need extensions to gain clearance.

Once the bolt is off you can push the shift rod towards the front of the car (some force might be required). I think it helps to be in 3rd gear at this point. You can see the end of the existing shaft seal in the above pic. It's face is orange in color and its rim is wider than the actual diameter of the cylindrical housing that protrudes from the gearbox.

Push the end of the shift shaft as far into the gearbox as you can. That gets it out the way as you don't want to damage it with tools whilst you are working here.

Pull off the old seal. I found that a large set of pipe grips worked well. I had to rotate them and pull N&S then W&E to work it free. Be VERY careful not to lose grip and scratch the end of the shift shaft. You do not want to abrade the surface of the shaft and its probably best to cover it with a rag or protect its surface in some way. In that respect, please note that my picture is WRONG !

Note that when you pull off the old seal you might not be able to see any damage or reason why it was leaking. Not something I fully understand but it seems to be widely reported. My guess is that the rubber goes soft and loses its rigidty or deforms just in a way which isn't really visible to the naked eye.

As you pull the seal free the oil will start to drip down so have a tray ready.

At this point its worth inspecting the shift shaft. Make sure the surface is smooth and if necessary smooth it with some wire wool or something similar. When the new seal goes on and over it you do not want any imperfections or burrs scratching and scoring the inner face of the rubber seal.

Here's the new blighter. It will cost you around £10.

Getting it on is a fairly obvious process. Just push it over the shaft and then into the hole. To get it flush you will need to use some force. I used a nice 22mm deep impact socket that was placed over the shaft and then hammered gently onto the face of the new seal to press it in. Just make sure that once again, you cover the shaft in a rag or something protective; gaffer tape at the very least. Then put your socket over.

Replace the boot (noting correct orientation) and its a good idea to put a new clean boot on. Then connect up the shift rod and screw the bolt back on using some blue threadlock. Tighten it to 13 lb/ft.

All you need do now is replace the protective undertray.



Just a small note which pertains to my car. As I was doing this job it occurred to me that my seal might have prematurely failed because of the modifications that I made to my shift rod. Back last year when I installed my RS quick shift I modified my shifting rod by removing the play in the coupler in order to make the shift more direct and positive. Now the RS shift rod does this but it does it by having no coupler but a univeral joint instead just before it mates with the shift shaft. My rod has no such provision for movement so with the engine swaying around under load/cornering and when braking, it's possible that too much strain is being placed upon the shift shaft and hence the rubber seal, by my solid shift rod. As a precaution I will now be installing the proper RS shift rod at the earliest convenience.

Update, May 2010. I have now done this but went for the Golden Rod as made by FD motorsports in USA. Its basically an RS rod but at less than half the price.




The Jackals Racetrack 1998 Richard Morris