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 ????

 

[Tx Jim]

I would take a WAG the problem would be a pressure control(relief) valve if tractor has one not the pump shaft. I'm not familiar with a 790 where is the hyd pump located(engine or trans)?

 

[dls790]

Toward front of left side of engine. Two pumps driven by one shaft and gears Any idea where the relief valve would be located? Also the screen had a plastic sleev over it is that normal?

 

[dls790]

Jim may I ask what the url is forthe 2 diagrams you sent me - I wanted to see if I could get the part numers for the various parts in each one. Thanks Dave S

 

[Tx Jim]

Sorry but I'm a computer dummy. I have no idea how to locate the url's. You can view the 790 parts catalog at JDparts.com. If you can't locate the PN's on JDparts.com I'll post them for you.

 

[dls790]

No problem - I own a computer service bureau (we specialize in circulation fulfillment-we keep the name/address info for magazines) and the best thing I can say about computers is I have some tech guys that fix what I mess up!!
I'll check out JDparts.com Thanks for your help. Dave S

 

[Tx Jim]

Check for PN's above with photo's.

 

[gpjones76]

I have the same problem.has this been solved?

 

[gpjones76]

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

Were you able to solve this issue,I have the same problem.

 

[beenthere]

gpjones76
Welcome to TBN.
You might send a PM to the members that might know that answer. Otherwise they may not "see" your question.
Member dls790 was last active May 2014, so been close to 10 years.
Maybe someone else will respond if you give a bit of up-to-date info of your problem, beyond "have the same problem". Tell a bit about the history of your problem, and what has been done to solve it by you. The more information about the situation, the better possibility of a member with a solution or suggestion for you.

 

[Fred Gerrells]

Toward front of left side of engine. Two pumps driven by one shaft and gears Any idea where the relief valve would be located? Also the screen had a plastic sleev over it is that normal?

Did you ever solve this issue? If so what did you do?