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TR6 Gearbox slips out of 3rd gear

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Ribbs

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I recently replaced my clutch/pressure plate assembly and used the opportunity to replace gearbox front and rear seals, as well as completely disassemble and rebuild the top cover. With everything back together, I'm now noticing that the car slips out of 3rd gear (and into neutral) when throttle balances forces. This is definitely a new issue and 3rd gear is the only gear that this is happening. I did not touch the gearbox itself as everything looked good visually. All I can think of is that I didn't get the detent ball and spring assembled properly, or the spring itself was weakened in the process. Am I overlooking any other causes?

Dave
 
I do not know this specific transmission. I would in general expect a bent or misplaced shift fork, bent or badly worn end on shift lever, or bad spring or poppet ball.

Bob Hustead
 
Question will it come out of gear every time. ? did you replace the shifting fork.? Did the locking set screw go back in its hole and tight .? Is the ball and spring in place on shift lever at bottom.? Third is the middle shaft and as you said you did not touch gears assy. I do not think weak spring missing maybe These gears are accustom to finding center under load. Go back to what you did last these gear boxes are built tough take the cover off again and look at middle shaft. Madflyer
 
My guess is either the detent and/or spring, as you thought, or less likely but possible is that the fork is not installed in the correct place on the shaft. If it's the fork, then it is not allowing the slide to move fully into 3rd gear, and thereby not fully engaging the detent.
 
I once had a similar issue and found that one side of the fork had broken off. Somehow the broken piece stayed in place and didn't fall into the gears. Will be interested to hear what you find with the cover off.
Tom
 
I had this happen on my GT6. All of the above mentioned could be true, but I found the thrust washers (dogs) between first and second to be the culprit. Third gear is at the end of the stack on the shaft, so any extra play/looseness on the end of the stack will space it away from the synchro/shifter. That was what was causing it on mine.

Rod
 
I am really not sure which vendor to use of the big 3 and perhaps a more specialized vendor like a trany shop that has a 4th option would be better. But anyways, I would replace the springs and balls or sometime they used cone shaped balls. Heck that would be easiest and most provable. My old buddy Barry Nelson who rebuilt tr tranys felt they were often the problem when the trany would pop out of gear. They are kinda adjustable by turning them in and putting a little gooop in the recess created by turning the screw inward, but a good quality new stuff would be best.
steve
 
sp53 said:
I am really not sure which vendor to use of the big 3 and perhaps a more specialized vendor like a trany shop that has a 4th option would be better. But anyways, I would replace the springs and balls or sometime they used cone shaped balls. Heck that would be easiest and most provable. My old buddy Barry Nelson who rebuilt tr tranys felt they were often the problem when the trany would pop out of gear. They are kinda adjustable by turning them in and putting a little gooop in the recess created by turning the screw inward, but a good quality new stuff would be best.
steve
Click to expand...

I don't know if there is any difference in the vendor's detents but I've had no trouble with the ones from Moss. I'm also not sure that replacing the springs and balls will have any effect if there is no obvious fault but easy enough to do (once you get the rugs out an tunnel off) and certainly won't hurt or break the bank.
The goop trick might put a little extra force on the balls which might help but don't over do it. The detents are only designed to hold the forks in place, not the gears. And speaking of that I've found that if the problem is internal, you usually can't hold it in gear with the stick.
Final thought, if you take the rails out, and you don't need to do that to replace the balls and springs, be aware of the interlocks on the back end of of the cover.
Tom
 
I just remembered something I noticed last time I built one of these...if the fork is reversed it can also cause a gear not to fully engage. That is, if it is installed 180 degrees out.
 
Interesting John. I didn't think that was possible. If it had been reversed how would it fit into the transmission with both the tranny and the cover in the neutral position?
Same with installing 1,2 an 3,4 forks on the wrong rails.
trans cover.jpg
Tom
 
Can't remember the details...I was working on 4 trannies covering 20 years of production at the time...8 years ago. I just recall noticing that it was possible to screw it up. There have been a lot of subtle changes to the forks and rods over the years.
 
I usually screw up anything that's possible to screw up so I guess I just haven't gotten around to screwing this one up yet. I did forget once to put the inter lock pin in though (among others).
 
Last edited:
Thank you all for the comments. I just put the car to bed for the winter (here in Ohio) and will have plenty of time to get the lid off for a look. Unfortunately, the detent springs/balls are held captive with the interference fit caps - not the threaded plug type. I guess this will be a good time to convert them. I'll be sure to post my findings!
 
The Bentley Book shows 1st-2nd / 3rd 4th have same spring and ball were Rev is different spring and tapered pin. So if pulling rods by hand are all the same most likely OK but pull should be 32 lbs and rev little less at 26 lbs not easy they use a scale but a large screwdriver should do. Any spring can brake as they are under pressure all the time. Madflyer
 
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