Gear cover/crankshaft oil seal

dpauly · Jul 11, 2025

Greetings. Replacing the crankshaft oil seal located on the gear cover of a Kukje (Branson 3120R, 2011) A1500 engine. Anybody know if the seal should be driven only until outer surface is flush with the outside of the gear case (which leaves a gap on the inside of approx. 1/8" between inner surface of seal and bottom lip of the crank bore of the cover) OR, should it be driven until touching that 'bottom' (obviously recessing the seal's outer surface 1/8" lower than flush with the outside? (Personally I cannot see where it would make a big difference but there must be some reason it's that way.) Is there a rule of thumb for such situations? Thanks in advance.

flyerdan · Jul 12, 2025

Having a little leeway on that could help if you have a shaft that is scored from the seal. You should be able to tell where it ran based on the mark, even if it isn't scored, if it originally ran flush with the outside and setting it back can run on a smoother part of the shaft, go for that. Be sure and put a small amount of grease between the seal lips so it won't start out dry, will last longer and not as likely to cause scoring.
Of course if the shaft is bad enough to require a speedi-sleeve, it won't matter. I'd probably seat it all the way down so it was in more securely.
Another reason for seating it all the way might be for clearance on the pulley hub that goes on the shaft, you don't want that touching the seal when it's rotating.

dpauly · Jul 22, 2025

flyerdan said:
Having a little leeway on that could help if you have a shaft that is scored from the seal. You should be able to tell where it ran based on the mark, even if it isn't scored, if it originally ran flush with the outside and setting it back can run on a smoother part of the shaft, go for that. Be sure and put a small amount of grease between the seal lips so it won't start out dry, will last longer and not as likely to cause scoring.
Of course if the shaft is bad enough to require a speedi-sleeve, it won't matter. I'd probably seat it all the way down so it was in more securely.
Another reason for seating it all the way might be for clearance on the pulley hub that goes on the shaft, you don't want that touching the seal when it's rotating.

Thanks, flyerdan. Your reply makes sense.