Kubota RTV900 no forward or reverse
- Thread starter boyler
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Greenorange
New member
I wrote this on behalf of my dad, but I know he still has it apart. He changed the brass plates, and replaced the charge pump. The pressure is only reaching 50 PSI still, and like you said it should be around 100 PSI and more. Filters etc. Have been changed too but still same outcome.
Wow, he changed the charge pump? That's in the differential section of the transmission and as far as i can tell you have to pull the transmission from the vehicle to do. I tore mine down a couple days ago. The bearing was smashed on the most external pump. Parts on the way. This thing only has 17 hrs on it since I last tore it down a year ago (yeah its been sitting for a long time) I tested my forward and charge pressure. Charge i get about 50psi at idle and about 100ish at full throttle which is what you test it at. Forward I have about 3300. Reverse I couldn't get a good reading because it kept stalling the motor. I found out my relief valve was out of spec though, so much that it can be adding 900 additional psi, so I'm hoping that's why it was smashing pump bearings. I did notice my 2 inner pumps have some valveplate wear with 17hrs, felt some tiny imperfections on the back of the pumps, but at 360 a pump i have to just send it. We just got 2 tracked pioneer 1000s, so the kubota isn't as important anymore.
I think the book says 73 to 105 at full throttle, I'll double check. Have you guys tried driving it with the diff lock on? If it moves with the diff lock or 4x4 on then its a drive train problem. What are the F and R pressures? should be between 3200 and 3800. Keep in mind forward and reverse don't mean the gear selector, they are in respect to the hydrostatic, it switches between forward and reverse while the vehicle is moving forward based on conditions. The reverse pressure is harder to test because you have to take a linkage off and manually stroke the pump backwards with a lever. If he changed all three valve plates, and the charge pump he would have seen if anything was broken inside like i'm dealing with. I would test F and R pressures, then try the diff lock and 4x4, check all linkages. If it slowly died while driving that's indication of some HST failure like i pictured. If it just stopped, that's more indication of a failure in the drivetrain. If it is all apart I would inspect the differential and everything around it. Sometimes a sheared shaft or spline is difficult to see untill you start spinning things and watch where it stops.
