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My rear main bearing seal is shot in my 51 235. The manual says the crank has to be pulled to replace the top half of the seal. Has anyone found a way to replace the seal without pulling the crank?

You shouldn't have to pull the crank to change the rear main. If it still has the old rope seal, it'll be kinda tricky getting it out because they tend to fall apart. I had to dig mine out with a small pick. Change over to the neoprene seal. You can change those without dropping the tranny and clutch. Good luck, because I've had about 4 of them in my 61 and can't get them to quit leaking!

There is a thread on this subject and I think an instruction under TECH. Part of the instruction involves providing a small amount of clearance to get the old one out. I tried this and I was unsuccessful. I was about to do a total rebuild so it was just an experiement for me. I don't see how the rear of the crankshft can move enough if the pilot bushing is in good shape.

prayer and patience try dropping the other mains a little also why does it leak?It is a good idea to replace the bearing

GEC52,

It is possible, but is a job that requires some proficiency to be done. Not all that hard, but can be done. You'll have to pull the oil pa(i)n, loose all the main caps bolts in a way that the first and second front main cap does not fall, remove the other (3 & 4) main caps, the crank will go down a li'l, then You'll have to remove the upper rope using a lot of patience, a thick wire may help a lot, try to clean the channel completely, You may use a small plastic bottle with querosene/gasoline/thinner to make sure it's clean, spraying the cleaner in there. Or any other stuff like carb cleaner. After it's all done, make it dry, slip a new neoprene seal, put new bearings on it, remove the ones in the engine, they should be worned out, and assemble it all carefully. remember to torque carefully the main caps, should be a good idea to replace the rod bearings also and prepare yurself to put the oil pa(i)n gasket carefully, so it does not leak and You'll be fooled thinking all this job took you into another oil puddle!
Hope it has helped.

Truckernix

It will go down a decent amount when You unbolt the main caps. There is a fair amount of play in the input shaft bearing, and remember the pilot is not all that tight into the clutch disc and into the bearing. In such a situation 1 or 2 extra milimiters - .040" to .080" is a lot of space to play. In fact it will go down much more.
I'd go the neoprene route also, would put a dab of glue between it and the block, and would also change the main bearings. Of course Dude that's what I'd do, and obviuosly I can be wrong! Just my 0.02.

Thanks guys,
That takes a big load off me. One thing though. Aren't the main bearings babbit also?

I would caution you about replacing all the bearings. There are a lot of factors to be considered there. If there is uneven wear on the crankshaft, the new bearings may not work out too well.

You asked about the bearings being babbitt ? Is your engine a low pressure model or a more modern one? The low pressure design had babbitt right in the rods and they had shims under the caps for adjustment. There is a procedure in the manual for this.

GEC52, I wasn't able to lower my crank sufficiently but that is in my estimation. Probably with some solvent, I might have gotten it out. In the end, I was doing a complete rebuild so I removed the crank and did it the easy way.

Maybe I was lucky but I recently changed mine and was able to grab the end of the upper seal with needle nose pliers and slowly pull it out. I replaced it with a neoprene seal, replaced the oil pan gasket and no leaks so far on a 30 mile trip. HLW