sub compact 755 john deere help

[barrentine934]

89 JD 755 compact tractor. Bought it from a man and he said it just quit pulling. It sat up for a while and the FEL,3 PT hitch and power steering didnt work. First thing I did was drained fluid and cleaned screen whith was very dirty. I put new low vis hi gard in and filter and I started tractor up.The FEL ,power steering and 3pt hitch worked fine but it still would not go backward or fwd.From what I understand the pump sucks the oil up through the suction line and into the hydrostat transmission? I broke the line loose where it connects the the hydrostat and there was not oil in the line.But my FEL and power steering works. Someone pls explain this and thanks in advance

 

[RustyA]

Is it possible the HST has a separate reservoir and filter?

 

[ROUSTABOUT]

Lost its prime. Hole in the line? Other screen for it or filter? If that screen was dirty I imagine other screens and things were dirty. Bit it sounds like a starvation problem or the pump is burnt up. Same pump does it all? I don't want answers, just giving suggestions for you to check. Sounds like there is another screen you haven't found yet. That stuff is made pretty tough. But if you keep playing with it and running it with the trans pump dry...

 

[jd110]

Is the lever next to your right leg in gear? It is a high low range lever, but there is a neutral in the middle of high and low. If that is in a gear, then my next guess would be you may have a broken bolt on the hydro drive gear. Hydro needs to be removed to repair, but a fairly simple fix. Worst part of job is fishing out the broken bolt head and washer that falls down inside the transmission. A long flexible magnet and a lot of patience will usually find the broken bolt and washer. If broken bolt and washer are left inside, there is a risk they will cause major damage if they get caught in some gears. There are other things that can cause your problems but I have seen this bolt broken more often than any other thing in my experience.

 

[barrentine934]

I removed the transmission and the bolt that you are talking about is fine. I did see that on another forum and it is in gear. I have tried both high and low. There is some reason that the oil is not getting to the charge pump. I havent found a leak in any of the lines that would cause it to loose vacuum. I did use a substitute for the low vis-hi gard oil. It may br too heavy to pull the oil thru?

 

[pmsmechanic]

"It may br too heavy to pull the oil thru?"

Not in summer. There is a problem somewhere else I would think.

 

[beenthere]

Has the strainer been inspected and cleaned?
Part Number M800489

 

[TractorGuy]

This is what the manual says for bleeding.

HYDRAULIC SYSTEM BLEED PROCEDURE
After installing a repaired or replacement part, air must
be purged from the system.
1. Fill transaxle with 17 L (4.5 gal) of John Deere
Lo-Viscosity HY-GARD® oil.
2. Start engine and run at half throttle.
3. Cycle all hydraulic lever functions several times.
4. Shut engine off and inspect hydraulic components and
fittings for leaks.
5. Check transaxle oil level again and add required
amount to bring it up to the full mark.

 

[jthibodeau89]

Looks like the 755 has a flow divider. Something is preventing the supply to the HST. Need a manual and gages to properly diagnose. My biggest concern would that the HST was run oil starved for a while. If the the cause of the oil stsrvstion was sudden, maybe no problem. HST charge pressure is on the order of 150psi.

 

[Dwellonroof]

I had a 755 and the hose #14 was sucking in air being cracked because of age.