John Deere 318 420/430 Differential Series Part IV

Starting to tear into the hydrostatic pump off a 420. This is a Sundstrand Model 15U pump. Unfortunatly things did not go as planned! It seems as though there is more damage to this pump than I originally expected.
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[@williamriley2528]

My 1989 420's differential 2 speed selection lever seems to be frozen in the faster speed position. Any ideas as to how to free it up...??? So I can get it back into the slow speed range...???

[@skylerrath6021]

Is there a way I can contact you? I have a 420 I'm troubleshooting that does have the pressure release buttons on top of the pump which is throwing me off because you said the 420's don't have them. I have no hydraulic power whatsoever. I'm 90% sure the problem is the gerotor pin but I'm a little hesitant to tear it down before I get a second opinion. Thanks!

[@MichaelTJD60]

The charge pump is a gerotor-style pump, while the valve body inside the unit is a piston-style pump. I'm surprised that gerotor won't come off easily...usually I have more trouble putting them back together than taking them apart. The dowel pin that locks the gerotor to the shaft usually falls out.

[@mmrbeef]

That has been my experience as well... normally I'm chasing the little dowel pin around on the floor because it has fallen out. I have yet to get the gerotor off the shaft.... studied it and pulled on it... studied it some more and my conclusion is the vibrations have caused the pin to wear into the gear and I need a tool to push the pin back into place. Just have to find that tool.... I've already ruined a couple small screw drivers. Haha

[@mackendw]

question for ya beef...is that bolt you mention just in front of the 2 check valves on the 420 what you loosen to remove the pressure in the system when you want to store the tractor for months of inactivity? mine leaked a lot of fluid after having put it in the barn and I guess it was due the pressure in the lines pushing out fluid in spots where the gaskets/seals were weak.

[@mhoch1736]

Where does the pressure come from for power steering and lift?

[@mmrbeef]

It comes from the charge pump.

[@marinefirstsarge509]

I appreciate the effort and I love your channel but maybe reshoot the video when you can actually do the tear down...

[@mmrbeef]

I will eventually get there... The gerotor or the gear on the shaft is still creating issues for me.