Overheating hydralic oil JD 7810

This problem started last May pulling 4 row striptill rig. Hydraulic oil overheat alarm went off. We changed filters with no change. Changed sensors and no change. Carried it to Dealer shop and they rebuilt SCV couplers with no change. Back to dealer and they rebuild SCV control valves with no change. Mechanic came to field and said fan clutch was weak. Changed it and engine ran cooler but hydo oil still hot. We finished planting without finding the problem. This summer all the tractor did was run rotary mower with no problem. Put harrow on yesterday and in two hours alarm went off. The transmission is quad range and I was working in B 4. I let it cool till the alarm went off and changed to C 3 and ran same speed at 1600 RPMs with no problem. Changed to C 2 and ran 1950 RPMs with no problem. Changed back to B 4 and in 20 minutes alarm went off. Immediately changed to C 2 with alarm still flashing and in two minutes alarm quit and never heated up again. We pull the planter in B 3. The next thing the dealer wants to do is rebuild the transmission to the tune of $8000.00. Any opinions out there of what the problem might be. The dealer seems to be fixing possible causes with out really knowing what the problem is.
 
Sounds like there is a HIGH PRESSURE LEAK . The steering , SCV boxes , rockshaft thermo relief valve, transmission clutch valve housing o-rings , PTO o-rings . Don't overlook the PTO valve . Start the tractor cold , feel the valve boxes for early heating .Usually but not always you can find the source . Push comes to shove start plugging feed lines . I don't see what a transmission overhaul would prove as there should be slippage in the two speed or the clutch if there is a leak there . Sounds like the dealer is a parts exchanger and not a diagnose and repair shop .
 
Dealer should be able to run a diagnostic pressure test. Should show if there is a high pressure leak in the transmission. By far cheaper than them throwing parts at it.
 
I agree with donmyeil..buy or borrow a hand held infra red heat detector,,locate a few key locations on the valves and transmission case,,you may even want to mark them with a paint stick with numbers start working the tractor and stop to do a reading,, mark this info down on a check list..then you can make some "educated" guesses..it will help narrow down the problem..
 
Probably the air pump Part of the transmission pump requires removing the front pump cover to access can be done with out splitting but not fun . The air pump helps push all of the trans oil back through the oil cooler
 
I'm thinking this has a pressure and flow compensated hydraulic system, which should operate at relatively low pressure when there's no hydraulic demand. (Probably in the 450-700 PSI range.)

Find out what the standby pressure is supposed to be for sure and check to see what it actually is on your tractor.

If the pump isn't destroking, likely it's pounding along at close 3000 psi, heating the oil.
 
If its a hydraulic system problem why does it only overheat in B range?? It did over heat 4 times in the ten mile drive to the dealer shop last year. It also ran probably 75 hours over the summer on the mower and that was in B range but not at full throttle with no problems. The dealer did run diagnosts on it as there was a stack of printouts in the cab when I picked it up. It pulls and shifts fine so its hard to believe its in the transmission unless there is someplace for a high pressure leak only when in B range.
 
I am assuming you have a 16 or 20 speed power Quad transmission. You say it only does it in "B" range. What power shift gear are you in??? When you running in "C" rage what power shift gear are you in???

The reason I am asking this question is this. The A,B,C,D and or/E are all mechanical ranges. They would not effect the hydraulics in any way. Now the 1-4 Power shift part is hydraulically operated. So if the transmission is only over heating in "B" range does it do it at all speed range selections??? So if it does it in B4 then running it in C2 and it does not then the trouble would seem to be in the 4 hydraulic shift. So you would need to be running in C4 to check that out.

Also you saying the warning light is going off. Is the oil actually over heating or is just the light/sensor saying it is over heating. You could have an electric issue rather than a hydraulic one.
 
The gears I was using are covered in my first post. Its 16 speed. It over heats in B 3 and 4 but not in C 2 and 3. I was not running the engine full throttle in C range so as to maintain same ground speed. The dealer used a temperature reader and it was hot. You could also smell it. I did not check it last week. The sensors were replaced last year with no change. Last year when it got really hot it would not move in any gear. It pulls good in all gears with no slipping now.
 
The most likely cause if oil is truly heating was correctly stated by Mr. 430wlpg. The air pump inside transmission PQ module normally builds pressure to transfers oil from the front of transmission back to the rear differential compartment. At higher road and planetary speeds the extra oil in the PQ module is being pulverized by moving parts which creates drag, friction and allot of heat. If problem occurs fairly fast at road speeds I bet your air pump inside of transmission needs attention. Good Luck, DW
 
I appreciate all the responses. I understand the workings of the transmission better now. The air pump is new to me but now I can ask the dealer shop about that. I just don't want to let them do an $8000.00 transmission rebuild if its not needed.
 
air pump is definitely a possibility, we had a 7800 power shift come in that was overheating the hydraulics when going down the road a couple years ago. if i remember correctly we actually had part of the air pump come out the drain plug or screen when we drained the oil and checked the screen. we pulled the transmission and went through it instead of trying to replace the pump with transmission in place.
 
Hi, we have the same problem with our 7810. We have had the gear box, 4wd box, air pump and hydraulic pump repaired/ new. still not solved the problem. Doesn't make any difference if the PTO is in gear or not, but only seems to do it with engine over 1700 RPM. had it on a little baler over the summer with hydraulic belt sledge but didn't get hot using that. Just wondering if you ever found the problem?
 
(quoted from post at 20:23:06 01/22/18) I appreciate all the responses. I understand the workings of the transmission better now. The air pump is new to me but now I can ask the dealer shop about that. I just don't want to let them do an $8000.00 transmission rebuild if its not needed.

How about another dealer that performs trouble shooting rather than guesses ?
 

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