Gearbox Noise

Jamie, I interpret whining and grinding as two different things. If it whines while just sitting in neutral with your foot off the clutch pedal, my first guess would be the large bearing on the input shaft is worn, giving the dry bearing sound you mentioned. If it grinds going into first and reverse, my first guess would be the clutch is not releasing as much as it should. Marc, you could also have the clutch-not-releasing problem. Check that first. If you decide the clutch is not the problem, then it sounds like your box may need its synchros lapped and get new bearings. Again there are different noises that mean different things. Identifying under what conditions it makes certain noises will help to pinpoint the problem. Do both of you have the factory manual? Look at the gearbox section and see if it is within your abilities. If you decide to rebuild your Moss box, we will be happy to help you through it. - Rob Reilly

Rob, Thanks for the reply. The sound is more of a "rough grinding bearing" sound, and yes I agree that if it is happening in 1st (which it is) the clutch is not releasing. It however is a different sound than the gear grinding into mesh. My first thought was the throw-out bearing, but symptoms don't match. The trans is quiet and smooth once the gear is fully engaged so I would rule out a mainshaft bearing. I will get under it today and adjust the clutch linkage and see if that helps. If you have any other thoughts I'm all ears. - Thanks Again, Jamie

If it sounds to you like something similar to a throw-out bearing, I still suspect the thrust washers and shims on the main and constant pinion shafts as the synchro sleeves do push these fore and aft when the shift lever is being moved. You could diagnose this by removing the interior to get at the gearbox cover and checking the endplay of the shafts while the box is still in the car. If things are worn enough to produce that kind of noise, you would probably even be able to see some damage. You could also try fishing around in the bottom of the box with a small magnet to pick up pieces of demolished parts to aid in the diagnosis. - Bruce Cunningham, '53 XK120 OTS

You also might be able to pick up some information by draining the gearbox oil into a clean container and fishing around in it with a magnet. If you have a small magnet that you can fasten to a wire, you might also be able to put it inside the box through the drain hole and run it along the bottom in both directions. The larger pieces of ground up parts will not flow out with the oil. I cleaned my gearbox out before removing it by filling it with kerosene and running it through the gears at idle speed with the wheels off the ground. This might also flush out some of the smaller pieces for diagnosis and makes it easier to work on it if you end up taking it out. - Bruce Cunningham

If you have any questions or comments send e-mail to: ted@jag-lovers.org
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