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Classic, Vintage & Veteran For Coventry and Meriden Models. Anything pre-Hinckley goes.

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Old 08-30-2012, 08:50 PM   #1 (permalink)
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Gearbox Leak - is it possible...

I've read the various threads for gearbox leaking on the primary side and have taken the time to replace all seals, including stripping down my tranny to get to the shaft seal. I've re-assembled everything including a new o-ring seal on the front sprocket with a thick amount of high temp RTV sealant on the splines, before the o-ring, after the o-ring and after the washer+lock nut are re-installed.

i took the bike out last night for the first time in a month of trying to find time to work on it. ran great, parked it, let it cool down, went down to wrap up a few loose ends unrelated and immediately noticed a small amount of gearbox oil on my floor. FRUSTRATING!!!

before re-assembly I even replaced the large bearing in contact with the sprocket. however I did notice a little bit of play here between the sprocket on the tranny shaft and the bearing. should there be a little play here? could this be where my gearbox oil is STILL coming from? Could the front sprocket have worn down where it comes in contact with the bearing? I can't seem to think of anywhere else the gearbox oil is coming from...
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Old 08-30-2012, 10:52 PM   #2 (permalink)
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I had the same issue with my '66 and I finally took it to someone more in the know. They found that the rubber plug on the end of the tube that the altermator wires exit through was missing and that fixed it. I was really frustrated because of all the work I had in it but still leaking. I know your wires exit the primary in a different place than mine but worth a check.
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Old 08-31-2012, 02:37 AM   #3 (permalink)
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Toby, thx, my plug is there as well as the rubber boot inside the primary that the wire goes through. Definitely got gearbox oil dripping, not motor oil.
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Old 08-31-2012, 04:59 AM   #4 (permalink)
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Have you sealed the layshaft blind needle roller bearing?
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Old 08-31-2012, 06:35 AM   #5 (permalink)
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Give this a thought, there is no seal where the front sprocket go's on the main shaft high gear splines, I know it's a pain, but to seal this at least you don't have to take the tranny apart, just the primary, with the front sprocket off - clean it's splines and then the splines it slides onto, a very light coat of RTV on both sets of splines should clear up tranny oil coming out and getting whipped around by the chain making a mess.
I just went through all this myself.

Bill G.

Last edited by mtnbkr01201; 08-31-2012 at 06:41 AM.
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Old 08-31-2012, 01:20 PM   #6 (permalink)
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Quote:
Originally Posted by mtnbkr01201 View Post
Give this a thought, there is no seal where the front sprocket go's on the main shaft high gear splines, I know it's a pain, but to seal this at least you don't have to take the tranny apart, just the primary, with the front sprocket off - clean it's splines and then the splines it slides onto, a very light coat of RTV on both sets of splines should clear up tranny oil coming out and getting whipped around by the chain making a mess.
I just went through all this myself.

Bill G.
Bill - that's what I already did, I've RTV'd the hell out of the splines, pre-o-ring placement, post o-ring placement, pre-washer, post-washer and my year bike does have the o-ring seal - 76 T140.

Caulky - I did RTV the back of the blind needle bearing as well.

Forgot to mention the sprocket teeth are in great condition so its not like my sprocket truly needs to be replaced (at least that's what I thought after removing it). Seems weird that the area where the bearing and sprocket meet would wear before the teeth but it's the only place left I can think of that isn't a perfect seal when you really look at the design of this set-up.

The last time i rode the bike before breaking it down I had what appeared like an explosion of gearbox oil all over the side of the bike and the sidewall of the tire which is why I replaced every seal the main bearing and the needle bearing plus RTV'd the shiat out of everything.

Last edited by furious furball; 09-01-2012 at 02:11 AM.
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Old 11-17-2012, 06:14 PM   #7 (permalink)
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Still dealing with this gearbox issue, here's some recent pics after disassembling everything and recap:

Oil vomits all over the left side of my bike, tire, rear fender during ride. I've even got a chain guard but oil gets everywhere. I've replaced both seals (large sprocket one & small shaft one), the large bearing and the needle roller bearing under the sprocket. I've applied (as seen) RTV sealant on the splines of the sprocket/gearbox shaft as well as before & after the o-ring and over the backside of the roller bearing. When I touch the shaft it has a slight wiggle to it and am thinking thru the RPM range if this wiggles then perhaps oil is seeping out due to that - basically appears the large sprocket seal and sprocket aren't making contact when wiggled so perhaps the large oil seal isn't allowed to do its job. Anyone out there experience this as ripping into the gearbox with uncertainty isn't high on my like list?

Gearbox Leak - is it possible...-t140-gearbox-leak-1.jpg
Showing the RTV sealant over the sprocket assembly with nut.

Gearbox Leak - is it possible...-t140-gearbox-leak-2.jpg
Showing the RTV sealant behind the nut (nut removed) in the splines and around the o-ring.

Gearbox Leak - is it possible...-t140-gearbo-leak-4.jpg
O-ring, washer and sprocket removed, shows RTV in splines. This also shows something rubbed against the RTV over the needle bearing backside. After removal of RTV behind needle bearing nothing is damaged and no oil is seeping out of it. Oil shown is left over from running the bike.

http://youtu.be/KWuuNNhyeWk
Here's a video showing wiggle in the mainshaft high gear assembly - is this within spec? How tight should the fit between the high gear assembly and large bearing be?
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Old 11-17-2012, 06:56 PM   #8 (permalink)
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Your Youtube video reveals the problem - your mainshaft 5th gear or the roller bearing it runs in, or more likely both, are absolutely shot. That is miles too much movement in all directions, and will definitely let oil spew out - there can be barely a moment's 360 degree contact between the sprocket and the oil seal when the bike is moving, or even just running.

You're going to have to strip the gearbox I'm afraid. But don't worry about it - it is not difficult to do and you won't need any special tools beyond what you must already have. The genuine Triumph manual explains reasonably well how to do it all, and it is virtually impossible to reassemble it wrong.

If you want better pics and instructions, Plewsy's videos almost ecertainly include a gerabox strip & rebuild, and if you go onto the T140.com forum, you can find an excellent illustrated gearbox strip & rebuild on there.

Don't despair - you've got to the bottom of the problem, just hope that the 5th gear bearing hasn't spun in the housing as that would mean an expensive repair.

Good luck with it, and let us know how you get on!
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Old 11-17-2012, 08:12 PM   #9 (permalink)
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im surprised that didnt lock up and have you off.
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Old 11-17-2012, 08:57 PM   #10 (permalink)
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Quote:
Originally Posted by JohnA View Post
Your Youtube video reveals the problem - your mainshaft 5th gear or the roller bearing it runs in, or more likely both, are absolutely shot. That is miles too much movement in all directions, and will definitely let oil spew out - there can be barely a moment's 360 degree contact between the sprocket and the oil seal when the bike is moving, or even just running.

You're going to have to strip the gearbox I'm afraid. But don't worry about it - it is not difficult to do and you won't need any special tools beyond what you must already have. The genuine Triumph manual explains reasonably well how to do it all, and it is virtually impossible to reassemble it wrong.

If you want better pics and instructions, Plewsy's videos almost ecertainly include a gerabox strip & rebuild, and if you go onto the T140.com forum, you can find an excellent illustrated gearbox strip & rebuild on there.

Don't despair - you've got to the bottom of the problem, just hope that the 5th gear bearing hasn't spun in the housing as that would mean an expensive repair.

Good luck with it, and let us know how you get on!
Finally a real answer, you can see how long this post goes back, thanks John A!!

Luckily I've been in the gearbox already so I'm just on this side of seasoned and it's not terribly difficult - Plewsys vids are the best. i recently replaced the high speed large bearing and it was a super tight fit and since then haven't been able to put more than 50 miles on the bike so hopefully you're right and that hasn't changed as I can expect I'd either need custom machining or a new case.

I see the high speed gear assembly out there is approx $150, MapCycle offers what looks like 2 kits, I wonder what makes the MapCycle kit $239...I know they have a tendency to upgrade to sealed bearings on other kits I'll have to call them.
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