trans rear seal replacement

[meridian]

I need to replace a leaking rear seal on my 36 DC. It is a BW on the back of a Lehman 120. Has anyone done this without pulling the engine/trans? I don't know if I have enough room.

[jleonard]

I don't know if you have room, but I could have room in my 40.
Maybe better done if you remove the trans and go thru it. Maybe you also could stand new clutch plates.
When you do replace the seal....remember to use RTV to seal the trheads before you re-torque the nut...which according to the BW distributor should always be replaced.
BTW, the trans on the Lehman can be removed without removing the engine. It weighs approx 125 pounds, not too bad. Replace the damper plate ($125) if you remove the trans. It is time to do it before it fails.
I rebyuilt my trans for about $450 5 years ago, and that included a manaul and a bench test before I put it back in the boat. Not a bad do it yourself job.
Cheers.

[mkh8911]

I just replaced the shaft in my 36 DC. You will probably need to haul the boat to get that seal out. The problem I had was the coupling is directly under a bulkhead and in a very tight place. If you slide the shaft back to the edge of the shaft tube you should be able to get a air impact on the tranny coupling nut and get to the seal. If don't mind laying on your belly like a reptile for extended periods, it should be doable with the tranny in place. The biggest challenge I had was getting the shaft coupling to slide back. It took 2 people (one inside, one outside) to get it moving. Hopefully yours will be more cooperative. Good Luck..

[meridian]

I'll be pulling the shaft out anyway to replace the cutless bearing and the packing gland.

[Shalamar]

I had leak at the rear of my transmission but it was not the seal, the oil was traveling down the spline to the coupling. The solution was to mark and disconnect the shaft and slide the shaft back. The large nut was removed(it was only slightly better than finger tight) and I put sealant on the end of the splin, inside the end of the coupling and on the washer then tightened the nut up to about 180 foot pounds. Spec calls for 240. That was two years ago and not a drop since. Mine is a 36 DC and there was lots of room to change the seal without removing the transmission.

[meridian]

how did you know it was the spline and not the seal?

[Shalamar]

I did not know it wasn't the seal until I had the coupling apart but I did have a suspicion it was the spline. The leak developed over a long period of time so I got a good long time to think and ask questions about a possible fix. The oil only leaked when underway and was always flung from the split in the coupling. (I had a splash hood over it in the end to limit the mess) There was no evidence of leakage when stopped. A friend of mine mentioned that he had seen a similar problem and found it to be the spline and he is a marine mechanic. I also found similar notes on the Internet about sealing the spline. I think JLeonard mentions it in his reply. Anyway I had the seal on hand when I did the job but it was not necessary.
Just for your consideration the nut on the end of my transmission is one and eleven sixteenths and the torque spec is over two hundred foot pounds so you will need some way to hold the shaft when removing and replacing it. I made up some tooling and got a cheap socket at Princess Auto(20$) including the adaptor. This would all be unnecessary if you have an impact gun. I did not put a new nut on but it may not be a bad idea, I just did not consider it.