In Reply to: Re: 641 Hydraulics posted by Tom on December 26, 2020 at 09:30:32:
The shaft seal is in the gear housing adapter. You have to remove the pumpfrom the tractor then remove the housing from the body (4 hex bolts). It is under spring pressure from the pistons. Dont loose any springs or pistons when you get it loose.
Once the gear housing is separated you have to unbolt the gear and drive the wobble shaft out from the tachometer drive opening. Then you can drive the seal out from the same opening. Dont damage the needle bearing in the nose in the process.
Its a bit of a bear to get that seal out. Check to make sure the wobble shaft bearing race is not obstructing the edge of the opening in the gear housing. If it is you will have to remove it as well. The back side of the race is tough to get to so I lay a cold weld around the face to shrink them so the will drop out. Drive in the new seal and reverse the process.
I would thoroughly check and eluminate all of the oring seals on the hydraulic manifolds before I tore into the pump. I would also replace the needle and wobble shaft bearing and race along with the seal. Expect to spend several hours on the seal job. And there is always the possibility the pump is simply worn internally.