B7800 with 2 problems

[trentj]

I have a kubota b7800 with 2 problems. First when and only when in 4 wheel drive it
pulls severely to the right. The 4 wheel drive works it just pulls severely. Secondly the hydraulics overheats after an hour or so of cutting grass with a woods mower. I changed the fluid and filter I put kubota fluid and filter back. Any suggestions on what the problem is. is there one or 2 problems

 

[Russell King]

For the overheating problem check if your radiator and any other cooling coils are clean on the finned side. There may be screen in front that is clogged with grass, seeds and dust or the fins themselves may be clogged.

Blow out with low pressure air to avoid damage to fins and blow from fan side outward.

 

[85Hokie]

I have a kubota b7800 with 2 problems. First when and only when in 4 wheel drive it
pulls severely to the right. The 4 wheel drive works it just pulls severely. Secondly the hydraulics overheats after an hour or so of cutting grass with a woods mower. I changed the fluid and filter I put kubota fluid and filter back. Any suggestions on what the problem is. is there one or 2 problems

for the 4wd....... jack the front up - spin left side...... what happens to it and or the right side wheel? To me it sound as if the left side is locked up and the right side is spinning twice as fast as it should - the spin rate would be a sign of something locking up left and resulting of pulling hard to the right.

 

[Roadworthy]

I've read the B series Kubota (or is it the BX) has a fan underneath in a vulnerable location. I think it's for cooling the fluid.

 

[Dave_eng]

I have a kubota b7800 Secondly the hydraulics overheats after an hour or so of cutting grass with a woods mower. I changed the fluid and filter I put kubota fluid and filter back.

It is not uncommon for owners to post on the forum about overheating hydraulic systems. Generally they reach this conclusion by feel.

Hydraulic systems are designed and prefer to run at moderately hot temperatures.

For comparison purposes, 130F will feel very hot to the touch. Hydraulic systems can run at up to 180 F and even higher.

Kubota's spec's provide viscosity numbers at 201F or 100 Celsius:: Super UDT Viscosity @100C is cST =8.1

Dave

 

[lugbolt]

100 deg F over ambient is normal. Figure 220 deg max temp and if it runs at those temps for a long period, you'll have to change the oil more frequently. generally speaking they don't hardly ever run that hot even in this climate where it's 100 deg F (or close) often, and for many hours on end. As said check the coolers, check for restrictions in the cooler hoses, and all of the lines/pipes leading to the cooler. Also double check your 3ph feedback adjustment if it has one (don't remember if yours does or not, I don't see those tractors very often). Usually when I see a B7800 or a B2910 (close to the same tractor) they're usually very overworked. Hey, it's got a nice big powerful 4 cylinder engine, let's use every ounce of power it has....but the problem is, it's still just a B series tractor....

the pull...have no clue...drain the oil from the cases and see if there's any metal shavings in the drained oil. Also check & make sure the front to rear tire size bias is within spec. Anyone replaced the tires on it lately? If the fronts dont' "match" the designed bias, in other words if you had the original rears on it and put larger front tires on it, your bias is off and that in itself will cause a pull among many other things

the fan comment made me laugh. The fan underneath is only on BX series and some of the other lawn & garden equipment. B series has a cooler near the radiator.

 

[North Idaho Wolfman]

First issue sounds like a front axle issue, like either a broken axle or some other issue that is causing one side to get more power than the other. this could be caused by a bad bearing, some other broken / binding part or possibly an issue with the differential setup.

Second issue could be caused by the three point staying active because of a maladjusted feedback linkage.
this will cause the hydraulics to push against the relief valve for too long causing overheating.