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evaluating gearbox prior to rebuild

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mcoomey Avatar
mcoomey Silver Member Michael Coomey
Paxton, MA, USA   USA
I acquired the pictured gearbox that I'm told came out of a '67 TR4A and it's been inside on my shelf since 1982. I have no other history on it, but I hope to use it in my '57 TR3.

I measured the synchro clearances to be 0.038 and 0.040 which is well within spec. Is there anything more that I can do to evaluate its condition without further disassembling it? I'm trying to decide how far to go with the rebuild. Do I just replace oil seals, o-rings, and gaskets and hope for the best -- or do I do a complete break-down and check bearings, bushings, shafts, springs, etc.?

As with my engine (for those who have followed all my inquiries), this will be my first attempt at a gearbox and the thought of pulling it all apart and getting it back together is a bit daunting.



Michael Coomey
Paxton, MA

'57 TR3

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tr4a_gearbox.jpg    41.7 KB
tr4a_gearbox.jpg

tr4a_gears.jpg    50.7 KB
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CJD john durant
Southlake, Texas, USA   USA
The weakest part of these boxes is the countershaft roller bearings. If the box is out of the car you should replace those as a minimum. The bad news...everything has to come out to get to them.

Other than that, you have checked all you can easily check. You could easily replace the input shaft seal. Other than that run it and see what you’ve got.



John
Southlake, TX

'55 TR2

titanic Berry P
Albany, Oregon, USA   USA
Michael-You might find these tech articles on the gearbox rebuild helpful (if you don't already have them). The same site has articles on the overdrive, too.

http://www.buckeyetriumphs.org/technical/Gearbox/GearboxDisassembly/gearboxdisassembly.htm



Edited 1 time(s). Last edit at 2017-10-01 10:33 PM by titanic.

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mcoomey Avatar
mcoomey Silver Member Michael Coomey
Paxton, MA, USA   USA
Berry,

Thanks so much for the link to the articles. I just took a glance at them and think they're just what I needed to give me the confidence to undertake the full rebuild.



Michael Coomey
Paxton, MA

'57 TR3

TR3barton Avatar
TR3barton John Taylor
Greenfield, MA, USA   USA
Hello,

That gearbox looks like it has a TR3 shifter. Since you had the top off is it a 4sp synchro?

You can tell if it is a TR3/4 box by the letters in front of the number.......sorry I do not know the"key"

mcoomey Avatar
mcoomey Silver Member Michael Coomey
Paxton, MA, USA   USA
I'm not sure about the shifter. If this is a TR4 gearbox it seems that the shifter must have been changed. Don't TR4's have an angled handle?

I'm assuming that it's a 4 speed synchro, but I'm a complete newbie here. I see 4 progressively larger main gears with 4 synchro rings. Does that confirm it?

The gearbox number is CT57990. I know that TR4 commission numbers start with CT but I'm not sure if that was consistent with the gearbox numbering.



Michael Coomey
Paxton, MA

'57 TR3


Attachments:
gearbox_number.jpg    35.7 KB
gearbox_number.jpg

mgruber921 Avatar
mgruber921 Marvin Gruber
Florence, Alabama, USA   USA
That is a full snych trans. Easiest way to tell other than the CT serial number is the rounded bulge on the trans body on left side. Non snych will have a flat oval there. They are pretty tough. If gears look good and snycros check ok I would install and use it.
Marv

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mcoomey Avatar
mcoomey Silver Member Michael Coomey
Paxton, MA, USA   USA
Thanks, Marvin. I think I'm going to take your advice and just clean it up, reassemble it and use it. I just removed the countershaft for inspection and it looks perfect, so I have to assume the bearings are in good shape also.



Michael Coomey
Paxton, MA

'57 TR3

titanic Berry P
Albany, Oregon, USA   USA
Michael-I would also check the 2nd gear "top hat" bushing, as they are prone to break at the brim. And while the gearbox is out, might as well check the clutch fork pin and cross drill the fork for a 1/4" bolt. The Buckeye site also has some excellent articles on the clutch (although they pertain to the diaphragm clutch used on TR4A-6). Also, the o rings in the top cover are prone to leak, so might as well replace them. Maybe ujoints and transmission mount. The party never ends.
Berry

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mcoomey Avatar
mcoomey Silver Member Michael Coomey
Paxton, MA, USA   USA
Berry,

Thanks for the additional advice. I was hoping to avoid removing the main shaft, but I don't see any other way to inspect the top hat bushing. I suppose it would be better to bite the bullet now that it's out of the car than to have it fail later.

I'm planning to replace the o-rings if I can ever get the lever cap off! It seems to have "become one" with the cover and a replacement doesn't seem to be sourced anywhere.

I've already removed the clutch fork and was happy to find that the pin was intact. By "cross drilling" the fork do you mean to drill completely through it and replace the pin with a bolt? Is this standard practice for a rebuild? I'd be concerned that it might weaken the fork.



Michael Coomey
Paxton, MA

'57 TR3

titanic Berry P
Albany, Oregon, USA   USA
Michael-Sorry if I gave you too much information or pushed your project beyond your intentions. The cap can be a pain because it is steel and the top cover is AL. Others will chime in on their favorite method to remove it. I don't think they are available new, but Marv probably has a box of used ones. The addional bolt on the clutch fork is shown in this (whatelse) Buckeye article on the clutch. It also discusses the cause of the pin frequently breaking. http://www.buckeyetriumphs.org/technical/clutch/ClutchShaft/ClutchShaft.htm
Berry

mcoomey Avatar
mcoomey Silver Member Michael Coomey
Paxton, MA, USA   USA
Berry,
No need to be sorry. Your advice is spot on. Of course I should inspect and improve the thing while I've got it mostly apart. I'm just being a little cowardly when I look at all those gears and think of the damage I could cause!



Michael Coomey
Paxton, MA

'57 TR3

CJD john durant
Southlake, Texas, USA   USA
Maybe you’ll find help here:

http://www.britishcarforum.com/bcf/showthread.php?100241-TR2-3-Gearbox-Rebuild



John
Southlake, TX

'55 TR2

mcoomey Avatar
mcoomey Silver Member Michael Coomey
Paxton, MA, USA   USA
Thanks, John. More good info and great photos!



Michael Coomey
Paxton, MA

'57 TR3

glcaines Avatar
glcaines Silver Member Gary Caines
Hiawassee, Georgia, USA   USA
Don't be afraid to tackle a rebuild of that transmission. I rebuilt my first TR3 transmission when I was in the 11th grade in 1967. I didn't even have a manual. The transmission had a tooth broken off a gear and when in 1st or reverse or both, I can't remember, it sounded like someone was hammering on the transmission with a sledge hammer. The local Triumph dealer sold me the parts he recommended that I replace in addition to the broken gear. I took a lot of photos while disassembling the transmission. The hardest part was getting all of the metal pieces cleaned out. Those photos were invaluable when reassembling. With digital cameras today it is much easier. The transmission had over 250K miles on it when I sold the car with no issues whatsoever. All of that being said, it is so easy to remove the transmission on a TR3 that I would likely just install it and see if it has any problems.



Current: 1973 TR6 W/Overdrive

Previous:
1963 TR3B W/Overdrive
1962 TR3A
1961 TR3A
1960 TR3A
1960 TR3A

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