RPMs vs Hydraulic fluid heat?

[MNBobcat]

Intermittent chattering of hyd's on CC system usually indicates insufficient supply oil to frt pump. Even though I know you stated post driver control valve had CC plug installed by dealer I suggest to remove male hyd tip on return hose. Aim this open return hose into hyd filler hole then with post driver valve in neutral engage tractor hyd control on dash & no oil should exit open hose. If no oil exits post driver hose during test then I'll suggest again to plumb your post driver directly to tractor hyd system by-passing the rear scv's. By passing scv's will give post driver more flow by putting return oil back into supply circuit.

I had to turn the pump back down to about 2000 pounds. At 2300 it chattered so bad it was unusable. I also checked the transmission filter and suction filter and they were both spotless.

The pounder is definitely set up with closed center and came off of a john deere tractor as well.

 

[Tx Jim]

I think setting stand-by to 2300 isn't the reason for chattering but possible lack of supply oil is more than likely the cause or internal high pressure leak. Just because post driver valve is stated to be for closed center operation does not mean it's a fact. Having been operated on a JD tractor doesn't prove it's for CC either.The o-ring inside of valve on end of CC conversion plug could have blown(see photo below). BTDT I still think you should perform the simple test of removing return hose male hyd tip activating tractor scv lever on dash and determine for sure that no oil comes out of hose when post driver control valve is in neutral.

 

[MNBobcat]

I think setting stand-by to 2300 isn't the reason for chattering but possible lack of supply oil is more than likely the cause or internal high pressure leak or worn stroke control valve seat. Just because post driver valve is stated to be for closed center operation does not mean it's a fact. Having been operated on a JD tractor doesn't prove it's for CC either.The o-ring inside of valve on end of CC conversion plug could have blown. I still think you should perform the simple test of removing return hose male hyd tip activating tractor scv lever on dash and determine for sure that no oil comes out of hose when post driver control valve is in neutral.

The manufacturer told me its set up for closed center. I did your test a week ago when I first set it up.

I agree the pump isn't getting enough oil. It seemed to me like I heard a bit of a knocking when I turned it up and i was wondering if the pump might be going bad.

 

[Tx Jim]

Knocking could be worn bushings in frt hyd pump drive coupling. Many frt pumps have been replaced on JD tractors only to find out it really wasn't the frt pump at fault. I'd suggest to check trans pump output which should be around 5 GPM.

 

[IceStationZebra]

Here is an interesting article discussing temperature effects on lubricants. 4570Man, you may be working above the critical temperature of your hydraulic fluid. The factory specs on my BX 25 are 113-131 degrees F. I cannot find the critical temp on Kubota SUDT2. Another question to track down an answer too. I have run my BH steady for 4 hours and the temp never gets to where I cannot put my hand on a cylinder. Do any tractors have a temp gauge for the HST? That may give a clue on range if it has a red line.

Temperature Stability of Lubricants and Hydraulic Fluids

Ron

Even though oil starts to break down around 140*F (specific addatives will vary, synthetic ~160) most systems can handle 180*F from time to time with a reasonable life. Cheap hoses and O-rings are usually the weak link. Piston pumps may also run into clearance and/or lubrication issues and result in lower limit. Usually 140-160 is the happy zone.

Hint - If you use an IR temp gun realize that chrome, zinc and trivalent plating (and possibly shiny aluminum) will give you false readings. Shoot painted or rubber parts and you cant go wrong.

ISZ