MGA-Register

Gearbox Oil Leak

I recently had an oil leak from the rear of the gearbox on my 1500 MGA. I immediately suspected that the oil seal needed changing. This I carried out by removing the prop shaft and prizing out the old seal and inserting a new one. Problem over I thought. But after a short run I returned to my garage and found that I still had an oil leak but worse than before!

I suspected that the seal I had used, although new, may have been old stock, so I ordered another. This duly arrived and I fitted it. Again after a short run I drove back into my garage and again oil was leaking from the rear of the gearbox. I decided to do a more thorough check of the prop shaft. Before removal I checked for any noticeable wear, my car has the earlier sliding spline type of fitting to the gearbox so by moving the sliding joint up and down by hand you can check for any wear, but there was no noticeable movement. I then removed it and carried out an inspection, paying particular attention to the universal joints. My car had always run very smoothly, with no vibration, so finding the universal joints in good condition did not surprise me. What I did find was that where the gearbox oil seal makes contact with the surface of the sliding joint it had in actual fact worn the surface of the spline creating wear (see picture) and causing the leak. On rubbing my finger along the outer spline I could actually feel a slight ridge.

I ordered a replacement sliding joint and am pleased to say that after fitting, and having driven a couple of thousand miles, I have had no further leaks.
Colin Grant.