Need opinions on my gearbox rebuild..

[TR4nut]

I'm rebuilding a 4-syncro od gearbox originally from a TR4 for use in my TR3A. I'm at the point of reassembly, and just noticed an issue with the input shaft:

One tooth has obviously broken off at some point, maybe from trying to go into 4th gear without a clutch, or simply dropping the darn thing in a previous rebuild. No metal remnants were detected when I tore it down.

I'm leaning pretty strongly towards using it as is - only one tooth is missing, and there remain 29 others in good shape. Anybody have a counter thought that this is a bad idea and I should source a replacement?

 

[martx-5]

Looking at the teeth to the left of the broken one, it looks to me that there is wear on the right side of those teeth. If that is the case, I wouldn't use that shaft.

 

[TR4nut]

I think it is mostly an illusion from the picture - the tooth is not cupped as it appears.

 

[tdskip]

Why mess around with it Randy?

 

[14dna]

JMHO;
I would replace it. If it is weak enough to break one tooth, how long before the others follow.
Would be a shame to have to do it over again.
Remember, this is just my thoughts.
Hope that helps.

Dave

 

[bgbassplyr]

I'd vote for the 'broke when dropped', because of the clean break. The rest of the gear teeth look pretty good with no abnormal wear that I can see and the broken tooth is for the syncro.

So, unless you are gong to race it or drive and shift like a wild man, I'd vote to use it.

But do what you think best.

 

[TR4nut]

Why mess around with it Randy?

Mainly because I don't want to go through the headache of sourcing another. If I had another on the bench I would of course swap it out just out of good practice.

Sourcing another one is doable, and I'll do it if needed - but I guess I'm questioning if this is truly on the verge of future failure. If you actually use the clutch properly, those little teeth shouldn't grind - and once they are in the sliding hub assembly its statically locked so I was wondering if I basically would be running with a gearbox that is about 29/30 or 97% of its original strength?

 

[TR3driver]

So, unless you are gong to race it or drive and shift like a wild man, I'd vote to use it.

 

[DougF]

Should you decide to replace it, Team Triumph should have a used input shaft. -Call Scott Harper @ (330)392-7176.

 

[glemon]

I would probably be leaning the asme way in your shoes, I might file or grind down where it broke off, it looks like the break might have left bits sticking out where they weren't before (but hard to tell for sure from the pic), just to make sure you don't get any interference or bits breaking off.

 

[TR6oldtimer]

I would clean it up a bit, use it, and not look back.

 

[TexasKnucklehead]

Randy... asking for opinions... here? What were you thinking?

My opinion is that's not really a tooth that is broken. When I think of a tooth, I think of a protrusion that mates with another (or a few) at any given time. That's more like a section of a spline, since all those 'teeth' mate with the shift collar at the same instance in time. At no time does any one "tooth" have any more stress than all the others, no matter how hard you shift.

Looking at the picture, it does look like it was dropped. It appears to be a clean break. If so, that explains why you found no debris inside. It was OK before and will probably be OK for another 50 years.

-but that's just my opinion.

As long as I'm giving my opinion, the lights tour last night was big fun. I was pleased to see that we're not the only ones silly enough to do that sort of thing on a cold night with the tops down. Thanks for organizing.

Jer

 

[TR4nut]

Thanks Jer-

Yeah, right now I'm definitely leaning hard to just putting it back together and seeing what happens.

And I appreciate the comment on the lights tour - we had fun although I'm surprised I lost about 75% of the group. Guess they couldn't keep up with the TR4. Or I shouldn't have told them where the pub was before the lights tour finished..

Randy