totalloss of hydraulics 790

[dls790]

I have a 10 year old JD 790 with a bucket & finish mower on it - was mowing today (12 acres) put it in reverse then tried to put in 2nd but it stayed in reverse. Now steering won't work, bucket & mower won't lift. The JD dealer said it could be a number of things and to bring it in.m I was wondering if it is the hydraulic pump died as it happened so suddenly. Any way to test it or any ideas what it may be? I hate to just take it in and be at the mercy of dealer that may take a few weeks to even look at it. Any help would be much appreciated. I tried the search but must be doing something wrong as no results Thanks Dave S

 

[dirt ditch]

Low oil level in the transmission could cause the problems your having. Are you using the right fluid in the transmission? JD calls for Low Viscosity Hi-Guard .

 

[dls790]

Low oil level in the transmission could cause the problems your having. Are you using the right fluid in the transmission? JD calls for Low Viscosity Hi-Guard .

The oil level was good and using JD HYGRADE. I was mowing and stopped to pick up a load of fallen tree branches that did not weight much when I tried to put it in gear it stayed in reverse then would not steer or lift bucket. Do you know any way to test shaft that runs the two pumps without taking the whole front end off the tractor.

 

[Tx Jim]

How long since hyd filter was changed and sump screen cleaned?

 

[dls790]

How long since hyd filter was changed and sump screen cleaned?

Pulled screen and it was clean. Putting new filter on. Tractor only has 390 hours on it. I doubt it was clogged filter as it was so sudden a disruption. Running fine put in reverse backed up a few feet then tried to put in 2 jd and it stayed in reverse with no steering or bucket hydraulics. I'm just at a loss. I pulled two pumps and they seem fine but haven't attempted to pull front end so I can get to pump. Drive shaft. That looks like a big job. Thanks for diagram that helps. Dave s

 

[bigbull338]

i would think the hydro pump went out.but you could try the simple things 1st and see if that fixes the problem.

 

[Tx Jim]

Yep I was taught years ago while employed at a JD dealership to "always try the simple,easiest things 1st"

 

[dls790]

i would think the hydro pump went out.but you could try the simple things 1st and see if that fixes the problem.

I checked oil level and using correct fluid checked screen and it was clean. What other simple things are there ????

 

[Tx Jim]

Change hyd filter and check pressure or lack of with a gauge.

 

[dls790]

Ok and if no pressure what do you think it would be ? The pump drive shaft or ????