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TR2/3/3A tr3 rear main seal


Country flag
Hey tr3 people I recently started that engine that I built and the back is leaking a little. Do they all leak a little? I put this thing together the best I could and did a meticulous job. I cleaned every thing like a hospital then used Indian Head gasket sealer and felt. It looked good and correct. I really do not want to take this thing apart and install an after market rear seal. I have the trans and clutch in, but the body is off the frame. Any suggestions? Should I just live with a slight leak or perhaps pull the trany and play around with the little aluminum1/2 shells in seal. Perhaps I did not get that right or maybe they are not sealing or bent or something. I mean crab, I do not want pull the crank.


Senior Member
They all weep a little unless you fit the retrofit rear seal kit. How much is a little? Mine drips about 5-10 drops after being driven. I just have the car parked over a sheet of fiberglas and wipe it up now and then.


Country flag
I am not sure exactly how much it is leaking. I have only run the engine in place for about a half hour. The leak has not actually fallen to the ground. The oil is just starting to form on the clutch inspection plate. I removed the plate and there were few drops on it. I cleaned and replaced the plate and the drops came back.


Country flag
They leak. The factory type "seal" is a closely machined surface with a corkscrew machined into the crankshaft to sling the oil back into the engine while it's running. As you already know from having it apart, there is no actual "seal".
The bottom of the bellhousing has the cotterpin through the hole to keep it clear so the leaking oil dosen't pool in there.
The only way to stop the leak would be to do the retrofit to the rubber seal type .
A properly aligned original type seal will leak but it shoulden't leak profusely. several drops after a run is normal. a medium sized puddle is too much.
It's just part of the character of these old beasts


Senior Member
If you just rebuilt the motor, give it about 1000 miles to break in. You might be getting preasure in the crankcase from the rings not being seated, causing the oil to be forced out the seals. Also check your breather to make sure its clean.
You could also try the TR-4A PCV system. It helps with crankcase preasure.
There are also shops that will blue-print your existing seal to closer tolerences.



Luke Skywalker

There is a special alignment tool for the original rear "seal" on the 4-cyl. TRactor motor. It's only of moderate use as there will still be some leaks (as already noted), just in the nature of the design. If you can find the tool, it still would require re-doing the installation, which isn't any easier than converting to a modern lip seal. The most leak free solution is still that lip seal conversion.

One thing, with a fresh rebuild you are likely getting a lot of blow by initially, until the rings are well seated on the cylinder walls (assuming both are new or at least the rings are new and the cyl. walls have been honed). That will exacerbate oil leakage to some degree, so it might improve a lot after 500 miles or so once the rings are more fully seated. I'd suggest just drive it and keep an eye on the leaks, to see if they get better or worse. The key thing to watch would be that oil doesn't build up to the point it might foul the clutch disk. All the rest of it is affectionately known as "British undercoating".



Country flag
Thanks to all for their hopeful advice; I think I can move forward now. I was really getting discouraged. Yes the engine does have new rings and pistons………. In addition, I do have a tr3 daily driver, but I had a machine shop put that crank in 30 years ago. And, yes it does leak a little; but I always chalked that up to the breather pipe. I am going to follow the advice of driving it and seeing what happens. Now I am going to put my energy into sandblasting and dipping the body tub. It would have been hard for me to put my heart into the body tub thinking that the engine should come back out again.
Thanks a ton sp53
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