B7200 HYDROSTATIC FORWARD/REVERSE INTERMITTENT ISSUE, HELP APPRECIATED

[CHARLESINMAINE]

The hydrostatic forward/reverse function works fine at times, other times not at all. Yes have manuals, changed oil, filters, cleaned strainers, check valves, high lo engaged not in neutral, oil flows to filter, linkage ok,
all hydraulics work fine,
has anyone else experienced intermittent hydrostatic function with no known differential between working and not working. I can walk up to it today and might work as new, 1/2 hour later no reaction to pedal forward or reverse, could it be an air or vacuum issue all hoses are new, tractor has 300 hrs .

ANY HELP MUCH APPRECIATED.

CHARLES

 

[torch]

Does the PTO spin? That would rule out a sticking clutch.

 

[CHARLESINMAINE]

Does the PTO spin? That would rule out a sticking clutch.

Yes PTO spins clutch is fine.
I believe it must be a hydraulic issue with hydrostatic trans. I can’t be the only owner that has experienced this?

 

[torch]

I have a B7100, not a B7200 and I'm not sure how similar they are. But I suspect the design principles don't vary much. With the B7100 there is a shaft sticking out the side of the transmission that is rotate by a plate connected to the pedals. Perhaps it could be intermittently grabbing if it's just clamped. But I think it's keyed. There is also a neutral adjuster with a lock-nut. Perhaps the nut has come loose and the adjustment is moving with the pedal?

There are also some internal relief valves to limit pressure. There's a charge relief and a high pressure relief. Perhaps one of those is sticking open. On the B7100 there are test ports to check the pressures when the pedals are operated. The FSM gives the procedures and expected pressures. There is also a vacuum specification on one port.

That's all I've got.

 

[rbargeron]

I'm with torch on this - there's a pinch bolt holding the arm on the shaft coming out of the HST case. I dunno if it's keyed - might be a just a serration that sometimes grabs, sometimes not. See if you can tighten the bolt?