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Wedge 4-speed gearbox problem

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stever_sl

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The situation: Our 4-speed gearbox was rebuilt a couple of years ago by someone with 40 years of experience on British car transmissions, but the car itself was in such bad condition that the restoration only got finished a week or two ago, so we could start driving it again. At first it was crunching and grinding quite a bit, unpredictably on up- or down-shifting in any of the gears, until the (new) clutch was re-bled. That sorted out a lot of the problems. Now, though, it rarely shifts cleanly from 3rd to 4th, often there's a noticeable crunch, and occasionally it's an outright noisy unpleasant grind. No problems downshifting back to 3rd. I've noticed that there's a constant growling when the car's in 1st gear too, and there's a very slight crunch when downshifting from 2nd unless the car is at a dead stop. So: Bad synchro on 4th gear? Residual clutch issues? Something else? There's a small amount of oil dripping from the vicinity of the shifter mechanism, if that means anything. And before installing the transmission into the car, and just afterward too, there was significant oil leakage out the tail end but the shop sorted that out - don't ask me how, I wasn't there and wouldn't have understood anyway. We're trying to decide whether there's anything we can do that might help the 4th gear grinding without just pulling it and having it torn down again. We drained the fluid from the gearbox and noticed a few metal particles on the drain plug but the fluid itself looked new, which it was. Refilled with GL4 but thinking about trying GM/Pennzoil Synchromesh to see if that helps at all. Any thoughts or suggestions would be welcome - or if anybody has a spare "known good" 4-speed gearbox lying around... :smile:
- Steve Richardson
St Louis MO
76 TR7 (original owner)
 
bobhustead said:
While I am not familiar with the TR7, your description sounds like inadequate clutch disengagement. Bob
Click to expand...

Talking it over with people who know a lot more than I do, they think that if it were clutch-related, it would be the lowest gear(s) that would be affected since their output speed is the farthest apart from engine speed. 4th gear should be closest to engine speed, so least work for the clutch. But it can't hurt to bleed the clutch again and have a close look at places where air could be getting in around the seals. Thanks!
 
Where is the friction point when releasing the clutch pedal? Near top, halfway up, close to the floor? Are the pushrods properly adjusted? If more than one hole in the throwout lever, are you hooked to the correct one?
Are both cylinders in good shape? If the fork pivots on a pin (as opposed to a ball) the pin could be sheared. Regarding the "close to engine speed" proposition, does the shifting work better if you double clutch?

Bob
 
The pedal releases about where all my cars do, around halfway up. I don't know about pushrods, I'll go out and check them against whatever the manuals say - good idea. Cylinders are new, or anyway as new as you can buy these days - who knows how long they've sat on a shelf somewhere? Don't know about pin vs ball, have to check. Someone who's much more knowledgeable about Wedges than I am (this car has been off the road since 1992 before its rebuild) drove it and tried double-clutching and at first we thought it was working, but then it started acting up again. That's the trouble with intermittent problems, they come and they go, and that can make you think that whatever you tried most recently did something good when it might not have. It seemed to me, the last time I drove it, that I had more trouble getting into 4th for about the first 10 minutes of driving, then I had a series of clean shifts. But I expect that was just the transient nature of this problem, and if I'd kept driving it I expect it would have started acting up again. Tomorrow I'll take it out for a good long drive and see what happens.
 
Seems GL4 is too heavy. TR7 site recommends Pennzoil Synchromesh oil. Need to look in manual as the original was an 80wt. But, should have no metal on drain plug.
 
Friction point sounds like it may be low. There is a very fine line between OK and not quite. The pushrod in the master should be barely out of contact with the piston (it should move slightly with side-to-side hand pressure with return spring disconnected). Same with the slave. If you set it this way and the pedal is too high, you can always adjust it down a little. New doesn't mean everything. When I was a BMC dealership mechanic, on one model of car (no, I don't remember which - 1970) we used to have to weld short extensions onto pushrods when one or the other was replaced. There is also (on earlier cars at least) a plate thru which the slave is mounted and which in turn is bolted to the bell housing that permits wrong-sided mounting of the slave. If your slave is so mounted, check that.

Bob
 
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