851 PTO Seal Bushing R R. (Long Post)

I have the center housing on the bench, stripped of pinion gear assembly , the axle housings and the ring gear assembly. The seal seat has a shoulder to the rear so the seal can only be driven out from rear toward the front of the housing. It was not easy to remove and as a result the seal was destroyed during the removal process. I don’t think I could have removed this seal if the housing was still attached to the tractor. The seal diameter is larger than the bushing. Each has to come out alone.

Directly behind the seal was the bushing that the PTO shaft runs in. This bushing (Part # NAA-798-A from NH) had to be pressed out of its location using a bushing tool attached to a hydraulic press. I don’t think I could have pressed this bushing out if the center housing was still attached to the tractor. Note, do not use the new bushing to press out the old. You will damage it. I used a bushing pressing tool and a hydraulic press. The bushing was already sized to fit the new PTO shaft so no additional sizing was required.

Next, the new seal was pressed into place. I was able to use a large hammer and seal-seating tool to install this seal. Again, it appeared to be much easier having the center housing on the bench.

All time involved to remove and replace new ran over an hour, I work slow and methodical.

Note, if the seal is leaking, more than likely the bushing is shot, allowing the shaft to wobble and damage the seal. Plan on replacing both.

That is about all I can think of to report on this project. I also replaced the outer seals, cones, cups, and collar on the rear axles today. If anybody wants a blow by blow on this project, I will fill you in upon request.

Could you describe some of the details for the ring and pinion removal etc. ? There must be some techniques or safety concerns you could shed light on.