JD 7520 hydraulic cooler flow

[Deere7520]

I posted earlier about my 1975 7520 having problems with the transmission overheating. I pinpointed where the heat is starting. The first point that heats up is the block on top of the transmission case front cover. The line that runs from the oil cooler in the front of the tractor runs to this block and is fairly hot the whole lenght. There are a couple tubes that connect at that block. One goes into the toruqe divider at the top. I'm guessing these are to circulate the trans fluid through the cooler. Is this run off the hydralic pump in the front of the tractor? All the hydraulic functions on the tractor work fine like steering brakes clutch ext. Is there a secondary pump that would feed or suck through this line or is it forced from the main hyd pump? Also are there any check valves or anything else that I should be looking for?
Thanks

 

[ihman73]

I'm not positive as I haven't dealt with the 20 series 4x4's much but it sounds like you have a blockage somewhere in the cooling circuit. Tim s could give you some better direction on these than I can. If you have a IR thermometer get it warmed up and shoot around and pinpoint the area where the temp changes and check it out. I'm assuming the cooler airflow is unrestricted.

 

[tim s]

The cooling oil comes from the oil that is returned from the actual oil cooler, sort of the bypass oil that the front pump is not using. Rarely is that oil flow a problem,,I'm still thinking a bearing or shaft is trying to gauld, and when it does that could be where it sets locked up tight...and those big ol Gals don't scoot well....I can see a complete transmission tear down in your future,,Darn it

 

[Deere7520]

Don't think I am questioning your thought of a transmission rebuild Tim. I'm sure you are right and it will need it soon. Honestly I don't have much money in the tractor and I am just trying to play around with it and get it running cool for now. I just thought it was weird how the tube would heat up more then the transmission case. If oil is pumped from transmission to the front pump then dumped through the oil cooler and back to the transmission I wonder why that tube would heat up first. There isn't any air restriction in the cooler. So if I start the tractor and let it idle and it would still heat up this line then would that make you think there is definetly a restriction? I haven't tried that yet but am thinking that could help me find the problem. I also might disconect this line that is heating up at the hinge and run a hose to a bucket and see how much oil it is moving. I'm not real concerned about breaking the tractor or having it locked up. I'm just using it in fields near the buildings now since I noticed the problem.

 

[4020guy]

I doubt an oil cooler restriction would bring that old 531 turboed and intercooled girl to her knees. Oil not only lubricates but cools as well. The sheer mass of the rear end is just slower to heat up than the 3/4 inch line. Like Tim sayes something is friction welding together inside the transmission. I'd pull it apart before you need another transmission case. I have a '75 7520 and feel for you. Good luck and keep us posted....Ron