JD 755

[EdMaine]

My 1988 JD 755 4WD will not move. I parked it on a hill (front uphill) overnight and when I went back to work the next day it would not move forward or back. The bucket works and the backhoe works so I have hydraulic power. When I lift the wheels, the front spin freely by hand (4WD is engaged) but the rear seem locked. The only issue prior to not moving was a slight chatter that began after I replaced a hydraulic hose. I didn't bleed the hydraulics after replacing hose, so the chatter is likely air in the system. Any suggested solutions will be appreciated. Thanks, <font color="blue"> </font>

 

[RobS]

Ed, does your tractor have HST or gear transmission? I can't help you either way but that information may trigger a thought for someone else /forums/images/graemlins/smile.gif

 

[EdMaine]

Thanks for the suggestion. The transmission is a Hydrostatic 2-range. I checked the hydraulic fluid level & it was fine.

 

[RobS]

I kind of suspected that it was a Hydro, and of course now I'm even less help for you /forums/images/graemlins/confused.gif

Did you check all the usual suspects though: safety switches ok, range/gear levers fully engaged etc /forums/images/graemlins/smile.gif

 

[Hambone]

Sometimes we miss the obvious. Parking brake released all the way? I had mine stick once, I released it but the pedal did not come up all the way.

Might look under for linkage that came undone (range select?)

Does it make any kind of noise when you are trying to move? Engine grunt ect??

Tried engaging diff lock?

 

[755inNY]

EdMaine,

I have never experienced this on my 755. Does the engine lug down when you step on the hydro pedal or is there no difference at all in RPM?

The manual only lists the following for "Tractor will not move with engine running"
>Park brake locked
>Transmission oil level low
>Transmission oil cold
>Engine cold
>Two speed axle shift lever in neutral

There is a seat interlock on the tractor. It will limit movement of the tractor if it is not engaged but I have never had mine prevent the tractor from moving at all. The interlock is a vertical shaft on the right side directly under the seat. It has a plastic hex top. The weight of the operator in the seat presses the shaft down allowing the hydro pedals to move. Every once in a while, in the winter, this shaft will get frozen in place and I have to bang on it to break it free. Maybe a combination of this interlock not working properly and cold or low fluid is preventing the tractor from moving.

Jeff

 

[tdenny]

Rob,

Just FYI the X55 series are all hydros.

 

[EdMaine]

Thanks to everyone for their help--this is a great site! I hope to really dig in to the problem this weekend. When I try to go forward or back nothing much happens and as I mentioned in my orginal post, the rear wheels will not move when off the ground while the front do (even with 4WD engaged) so a stuck brake is a maybe. Safety switches seem to be ok and all levers seem to be engaged as they should be Hambone&755inNY--no the engine doesn't grunt or lug down nor is there any noticeable noise when I am trying to move (a slight indication that it's trying to do something --but very faint). Seat interlock seems to be fine & it was not that cold (I've use the 755 for plowing in many of very cold Maine winters without an issue.

Hopfully, this weekend will shed some light on problem -- hope it's not major /forums/images/graemlins/confused.gif <font color="blue"> Thanks again for all the suggestions.</font>

 

[OkieG]

Ed,
Did you try both High and Low range? The "cover plate" that has the detent slots (Rabbit, Neutral, Turtle), can sometimes slip. If the cover plate slips up or down a bit, it could move the detent slot to where the transmission is disengaged.

I've not had that happen on the Hi-Lo Range Selection lever, but have had it happen on the PTO Selection lever. If that is the problem, the cover plate is easy to adjust to get the lever back in proper alignment.

OkieG

 

[tdenny]

I've had the same problem as Okie with my PTO selector. The only time the tractor wouldn't move when I depressed on of the hydro pedals is when I had the loader dug in and forgot to raise it. Gosh I hate to admit that one. /forums/images/graemlins/grin.gif

 

[ibboatin28]

The parking brake does stick sometimes on mine. But if this is what it is the pedels are hard to push and the engine pulls down. Hope this helps.

 

[BigEddy]

My 855 is essentially the same tractor. Here's what I would do.
First - Try the stuff already listed. Make sure the parking brake is off. Put it on, take it off, make sure it is working.
Make sure the range selector isn't in neutral, try it in high and in low.
Make sure you are sitting on the seat, as it controls the safety switch already mentioned.
All the obvious stuff.

Then if this doesn't work, look at your Hydro pedal linkages. Do they move or not. If you follow the linkage back, the pedals connect to a lever on the actual hydro tranny. On mine, I had the bolt break and fall out. So I could move the pedals, but the tractor wouldn't move. Replaced the bolt and things were fine. Nice thing about these tractors is by looking under them it's pretty obvious what's connected to what.

Still not working, use the outriggers to lift the tractor, put it in neutral, and try to spin the rear wheels by hand. Has to be in neutral or the hydro will hold the wheels. Spins - brakes are fine, Stuck - most likely brakes. Front wheels aren't a good indication, as the diff will allow them to move even if the trans is jammed. Then put it in 2wd, low, and use the trans to try to turn the raised wheels.

Should give you lots to start with. I'm assuming it worked fine when you parked it, and nothing "happened" that you noticed.