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TR2/3/3A TR3 Rear Main Seal


Jedi Hopeful
I realize this topic has been beaten to death over time but still could use some information. It turns out my transmission in my car that I've finally gotten running about half right isn't much good. There is a noise in reverse and it is difficult to get into 2nd gear, All others are okay. I've decided to swap it out this winter for a TR4 transmission my buddy has. The question is can I also renew the rear main in the engine with the transmission out and the engine in place? The engine is a fresh rebuild by the previous owner and leaks rather badly. I've read her of others having the same problems with new seals. I believe I will go with the seal that sells for a hundred dollars (got the name somewhere).

Thanks, Donnie


Great Pumpkin - R.I.P
I don't believe there is any practical method of installing the rear seal correctly with the engine still in the car. The problem is that you really need to have the crankshaft out to either use the setting mandrel, or to wrap the lip-type seal around the crank surface.

To get the crankshaft out, you have to first remove the fan, so you can remove the dog bolt, front hub, timing cover, timing chain, etc. While it might marginally be possible to remove the fan by moving the radiator as far forward as possible and then working between it and the fan, I kind of doubt it.

Then the next problem is removing the dog bolt and working it out through the hole in the radiator. Again, it might be possible but I doubt it.

Then the crossbrace has to come out. I have done it with the apron on, but it wasn't easy.

Now you have to remove the front hub without banging into the radiator or bending the pulley flanges.

I think by now, you are already past the point where you might as well pull the front apron and radiator; and then pull the engine & transmission as a unit. Doing the gearbox R&R with the engine in place is kind of a hassle too.


Geo Hahn

Country flag
What he said, plus...

oxendine said:
...The engine is a fresh rebuild by the previous owner and leaks rather badly...

Do you know what sort of seal was used at the time of the rebuild? There for a few years (not long ago) there was a modern-type seal conversion offered that required machining the crank. I've heard that many of these kits specified a machined crank diameter that was too small, resulting in a modern seal that leaked much worse than the original scroll-type.

Before you order a replacement I think you will want to know what's in there now -- either by inspection, documentation or asking the prior owner (if that does not require a Ouija Baord).


Great Pumpkin - R.I.P
Good point, Geo. I believe the latest "improved" seal, the "Viton" design by Chris "Mad" Marx can be used with a crank that was mis-machined for the earlier lip seal. However to get maximum sealing effect, it really needs to be used with an unmodified crank. If you want to go that way and your crank has had the scroll ground off, it might make sense to look for another crank.

AFAIK the Chris Marx seal is only available through ARE (Joe Alexander) and TRF in the US. Other vendors (Moss et al) are still selling the "machining required" seal. And I have heard some folks say that even the current instructions have too small a diameter specified for machining the crank.


Jedi Trainee
Country flag
I thought The Roadster Factory offered a rear seal kit that did not require modification to the crank. The kit included a modified oil seal assembly.
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