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Gone fishing for first tooth

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T

TexasKnucklehead

Jedi Knight
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Those of us who fail to learn the mistakes of history are doomed to repeat them...

I'm driving home from the club meeting today in the TR6 and stop at the guard shack to drop off my temporary subdivision access key. When I pull out normally, I hear a noise I've heard before (https://www.britishcarforum.com/bcf/newthread.php?do=newthread&f=18). A loud tick in 1st gear, only 1st gear, and no other time. -It even happens when coasting down the driveway with the clutch depressed and 1st selected.

I removed the drain plug, and dragged a magnet across the underside of the case until the broken tooth fell out the drain hole. This is by far the most interesting fishing I have ever done. Though the catch was expected, and I was happy about catching it, I'd have preferred not to.

The last tooth was broken off 1st less than 5,000 miles and a little over 2 years ago. What am I doing wrong? What do you think about driving it with a tooth shy of a full set? How much more damage could I do?

Jer
View attachment 26217
 
The tooth next to the broken tooth is going to be taking a lot more load, right at the tip where it is thinnest. Will probably work for awhile, but eventually it will let go as well. Which won't leave you much worse off than now, unless the broken tooth just happens to get jammed between the gears instead of just falling harmlessly to the bottom. It's thought that something similar happened to this gearbox:

untitled.JPG
 
Randall, that is a scary picture and I understand how catastrophic a floating tooth could be. That's why I wanted to remove the bit I thought was in there. The neighbor would be more strained and (more) failure is probable.

Since I live in Texas where roads are fairly flat, and rarely have to pull out on any sort of incline, I could skip 1st gear and start pulling out in 2nd. The driving experience will be somewhat reduced, but it's better than working on 2 TRs and having none to drive when the best driving season is quickly approaching and could be gone before I'm properly repaired.

I understand that no one has a crystal ball, and I will not hold anyone liable, but I would appreciate your thoughts.
 
Jer, having two projects at the same time is the pits. I had that happen only once. I'm inclined to go with your idea of not using 1st gear, the TR6 has plenty of power to start off in 2nd and like you said your pretty much in the flat lands.
 
Just because you dont select 1st does not stop it being driven.
All the gears mesh with the layshaft all the time.
All that happens is the gear is not locked to the output shaft unless you select it.

Have you ever replaced the layshaft bearings?
Have you replaced the spigot bush between the main and input shafts?

If not then maybe this is why you are breaking teeth.
Al.
 
alanjohnturner said:
Just because you dont select 1st does not stop it being driven.
All the gears mesh with the layshaft all the time.
All that happens is the gear is not locked to the output shaft unless you select it.
Al.
Click to expand...
Yes, I understand how it works. But when 1st is not selected, the force on the teeth should be less than when "pulling hard" in 1st.

alanjohnturner said:
Have you ever replaced the layshaft bearings?
Have you replaced the spigot bush between the main and input shafts?
Al.
Click to expand...
Yes. As well as the shaft, upgraded bearings, and both (main and counter) 1st gears as well as any worn bushes or out of spec spacers.

alanjohnturner said:
If not then maybe this is why you are breaking teeth.
Al.
Click to expand...

I don't know why I've managed to break a 1st gear tooth, twice. The 1st time I replaced the gears was because the needle bearings came apart and destroyed the inside of the 1st/counter-assembly as well as the shaft. The second time I used a used 1st gear set from a later model with different sized gears than the original (used the matched set). The first time I was pulling out very hard, with over sized tires, on grooved concrete. This time I was doing nothing unusual. Go figure.
 
Having learned to work on Chevy's and trucks...I still laugh every time I look at a Triumph counter gear. It's so little!!

I don't think it's anything you did. Its just a light weight design after 40 years of service. As long as you are sure it's one of the 1st gear teeth, you should be good with your plan to skip 1st. If its off the large gear on the counter...or the small gear on the input shaft, then it is loaded in every gear but top. I would think you would still hear the clicking, though if that's the case.

Sorry...this stuff always happens at the worst times...
 
It's not very likely, but you may have picked up a couple of defective 1st gears. When you go shopping for your next one, you might want to try a different source.
 
Said it before, get a supra tranny sooner than latter, 82-85.Get them before the supply dries up,
then get the Eagle gate kit.If you think any amount of babying will make an old brit tranny anything more than a relic
then I have some fine swamp land you gonna love.....
MD(mad dog)
 
"Dump that 3 and get a 240Z from the land of the rising sun."
 
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