Broke Hydrostat twice? Why?

[wheelsofsteele]

 

[texasranger556]

IMO It doesn't look too bad from the pics. If you can't find replacements I'd take a few thickness measurements of the plate with a mic to keep as reference then start lapping. Keep going until the whole face is a nice copper color with no grooves. Use progressively finer grit up to 2000 or so.

For reference, here is a valve plate out of a hustler zero turn that was too far gone.

 

[dfkrug]

IMO It doesn't look too bad from the pics.

It looks fixable to me as well. Hard to tell from the pix how deep the wear is, however. The
cause has to be found and corrected first, of course.

 

[texasranger556]

It looks fixable to me as well. Hard to tell from the pix how deep the wear is, however. The
cause has to be found and corrected first, of course.

Good point. Were you able to measure pressures before tearing into the hydro? Again, it's hard to tell depth from pics but it is somewhat surprising that the valve plate grooves alone were enough for you to suspect a drive shaft failure. Did the transmission chatter when pushing the fwd or rev pedal? Would it move at all?

If the trans has a built in charge pump I would inspect it closely while you have the trans apart.

If it's charged from the power steering pump like my 4400 then you'll have to put everything back together to measure the charge pressure.

 

[dfkrug]

Good point. Were you able to measure pressures before tearing into the hydro?

The OP, Bob, posted the data measured by the dealer when he took it in, 2.5y ago. It is in Post #1.

I got the bad HST only to do the post-mortem on it, after it had been replaced.

Maybe Bob will post an update on how his tractor is working?

 

[texasranger556]

The OP, Bob, posted the data measured by the dealer when he took it in, 2.5y ago. It is in Post #1.

I got the bad HST only to do the post-mortem on it, after it had been replaced.

Maybe Bob will post an update on how his tractor is working?

Sorry I meant to reply to wheelsoffsteel whether he checked anything before tearing it apart.

 

[fatjay]

The pistons are never supposed to have any surface movement. There's supposed to be a bottom ring + bearing ring + top ring and the top ring is what is supposed to hit the pistons. The top ring should freely slide on the bearing ring so that there's no friction between the top ring and the pistons.

The swash plate should have that sandwich of rings sitting on it. I recently did this and all the parts were available from messicks, it honestly wasn't hard. I will say, your pictures are infinitely better.

 

[texasranger556]

The pump slippers actually have radial surface movement against the top ring due to the changing geometry as you stroke​ the pump. When the swash plate is flat the slippers travel in a circle, but as the pump is stroked the circle turns into an ellipse with respect to the top ring.

 

[LouNY]

I just finished reading this entire thread from post #1 to #188.
This has been an interesting read and a fairly informative post.
To me it confirms the need for good filtration, quality fluids and preventive maintenance.
One thing missing is the huge importance of a warm up period in cold weather to avoid suction cavitation
and suction filter bypassing. Also high temperature will degrade the fluids, but it is also possible to keep the
temperatures to cold all fluids need to get warm enough to cook the moisture out of the system, people in the desert
might not have to worry about but any one in humid areas with varying temperatures has to worry about water
moisture in fluids from cavitation issues to ice crystals. I like to see temps getting into the 180 F range on the hottest return point
unless you are running a water absorbent filter in the system. A lot of heavier equipment use transmission and hydraulic heaters
in addition to block heaters to reduce cold start system issues.