John Deere 6410 Hydraulic system overheating

[JLA-SA_PY]

I'm having trouble with the hydraulic system overheating on a John Deere 6410 that was built in Germany. The whole transmission gets very hot to the touch, at times it has gotten so hot the transmission does not shift between forward and reverse anymore. Quit a bit of diagnostic work has been done by various individuals, and it seems the issue is that there is not sufficient hydraulic fluid flow through the cooler. A service man checked over the clutch packs and they were in good condition. When the transmission is hot to the touch on the outside, the lines going to the cooler are just a little warm. Running the tractor with the cooling loop open puts out very little oil, maybe about a gallon per minute. I understand the the cooling loop gets its oil from the bypass of the system pressure regular, so it seems like oil would be getting away somewhere inside the transmission and therefore there is not enough left over to run through the cooler and cool the system. The hydraulic pump inside the transmission in new. Would anyone be able to give any suggestions on where the oil might be getting away? Any certain ports we should check pressure on?

 

[Harry in Ky]

You might get better results if you mentioned what transmission your tractor has. How would anyone out here know where to start?

 

[JLA-SA_PY]

Sorry, I forgot to mention this tractor has the PowerQuad transmission with the mechanically activated reverser.