BILLYFNEW
New member
Can some one point me to this thread. I have tried using the search to locate it but can't seem to get far enough back. Thanks so much,
790 - Raising Hydraulic Pressure
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tomrscott
Gold Member
I have seen a thread somewhere about this also. My JD dealer is very negative on the subject, but I guess they have to be. Apparently they had a customer that jacked it up beyond 3000 psi, the tech thought it might have reached 3800 psi, but I don't know if that is even possible. Anyway, they claim that after a few months the machine was blowing seals and the customer was unhappy. Don't know how much of that is accurate, but I suppose it is possible.
On the other hand, I would be very surprised if 2500 psi would cause any problems at all. I am very tempted to put the shims in mine.
I just took delivery today, so I will probably wait awhile and make sure everything seems fine first. But I do have a big chunk of steel I'd like to pick up that I have estimated to weigh 1500 pounds or so. With adequate ballast, I think a 790 ought to be able to lift that safely, but I am pretty sure the stock hydraulics won't get the job done. I can probably pick up one end at a time and drag it around, but I'd like to be able to put my forks under the middle and carry it.
One thing I think I will do, either way, is to install a pressure gauge. I thought I would get one that went to 3000 psi full scale, panel mount, with the hydraulic fitting on the back and see if there is some good place to add it to the console. I want to be able to monitor how high the pressure gets and not be guessing.
On the other hand, I would be very surprised if 2500 psi would cause any problems at all. I am very tempted to put the shims in mine.
I just took delivery today, so I will probably wait awhile and make sure everything seems fine first. But I do have a big chunk of steel I'd like to pick up that I have estimated to weigh 1500 pounds or so. With adequate ballast, I think a 790 ought to be able to lift that safely, but I am pretty sure the stock hydraulics won't get the job done. I can probably pick up one end at a time and drag it around, but I'd like to be able to put my forks under the middle and carry it.
One thing I think I will do, either way, is to install a pressure gauge. I thought I would get one that went to 3000 psi full scale, panel mount, with the hydraulic fitting on the back and see if there is some good place to add it to the console. I want to be able to monitor how high the pressure gets and not be guessing.
I owen a 2003 JD 790 W/ 419 loader at 30 hrs I did the hydraulic boost w/ the shims (one pack) .... And it works GREAT!!! ...I now have 70 plus hrs on it most of witch have been loader work ...before the boost ,I was very disappointed in the loader ... would not even lift the rear of my Ford Ranger . /forums/images/graemlins/mad.gif..Now it's no problem... would do it again .... Loader will pick up the front of the tractor now without cruling the bucket...... for more info got to tractorpoint.com ....all I can say is that it works for me!!!!!! /forums/images/graemlins/grin.gif
tomrscott
Gold Member
Did you measure the peak pressure increase?
What is that Shim Kit part number?
What is that Shim Kit part number?
The increse in pressure is about 20%..... before adding the shims... max pressure was 2045 psi .... after installing the shims ....max pressure is right at 2500 psi ....from the notes that I made ..... The part # for the shim pack is AM 875169 that's a JD # ....IF you decide too install the shims I think you'll be glad you did ... /forums/images/graemlins/smile.gif but only install one pack ... I have heard of people installing more that one pack and razing pressure to 3000psi or more ... anything over 2500 is too high /forums/images/graemlins/blush.gif.....besides the one pack is all you need....it will make a big inprovement .........Best of luck ...Great little tractor...congrads on your new 790 /forums/images/graemlins/grin.gif
yugo
Bronze Member
Mr. Scott - I know you didn't ask me, BUT, I worked on hydraulic systems for 30 years. Increasing the pressure over factory specs will create a lot of trouble in the near future. The hydraulic pump and drive, plus any and all seals in the entire system will be likely to have early failure. In the perfect world, it's best to set the hydraulic pressure down, for longer maintenance free use. Example: You can haul over a ton of material in a half ton pickup - but for how long. Good luck - Yugo
If you want more info on it go to tractorpoint.com and do some research on it ...theres alot of owners on there that have done it and have alot more hrs than myself ..... like I said the shims made a big improvement on my tractor .... I would do it again in a heart beat.... it's your choice and your tractor ,...best of luck on whatever you decide... /forums/images/graemlins/wink.gif
tomrscott
Gold Member
Yugo,
You said raising pressure over "factory specs", and generally I would agree, but I think this may be a different situation. I believe all of the components in the 790 and 419 FEL are rated as components to be useable at far more than the 2050 psi that JD sets the pressure relief on the 790. I believe the lowest rated parts are rated for use to at least 2500psi, but they may all be rated to over 3000psi. All of the hoses and other fittings are rated for use at well over 3000psi. I am not talking about cutting into the safety margin either, I am talking about the recomended safe operating specs.
I believe that JD sets the pressure relief so low on the 790 because their lawyers have run amuck with excessive caution over risks of liability litigation and become convinced that the tractor should not be able to lift enough weight that an unballasted tractor could tip over on a side slope, with the loader at max lift. Rather than tell you you need X amount of ballast if you are going to lift Y pounds, at some slope angle, maybe a safe operating limits chart, JD sells a 30hp tractor is only rated to lift a little over 600 pounds! They set the hydraulic relief valve to a such a low value in an effort to make it very difficult to get in trouble. It's like a "governor" on the throttle of a go-kart track at an amusement park to keep inexperienced drivers from getting in trouble. It isn't that the system can't safely perform better, but they don't want to be responsible if you don't know what you're doing.
The trouble is, some folks get carried away with this and decide if 2500 is nice, 3800 is even better. Then I agree they are asking for trouble, but I have a hard time believing that 2500 psi will cause a problem. JD has just become excessively cautious. I really don't believe this is an issue of overloading components past safe operating limits, but some lawyer's idea of making a "safe" tractor. Those of you who are firearms enthusiasts will recognize this from the talk we've heard about making "safe" guns and "safe" bullets. It is truly a whacky world we live in.
If I add about 1000 pounds of ballast, bringing the tractor over 3000 pounds gross weight. at that point I should be fine picking up considerably more than 600 pounds. I know enough not to be very careful if I lift a max load very high, or on a slope. I am happy to take responsibility for what I do with the tractor and wish the lawyers would stay the heck out of it. Today I tried to lift one end of a 19' steel plate that I've calculated to weigh about 1500 pounds, and I couldn't even lift one end of it six inches. With a completely unballasted tractor, I couldn't even get the back wheels off the ground lifting with the loader. I could just barely unstick the steel plate from the ground and shove it around. I just think that is silly for a 30 hp tractor.
You said raising pressure over "factory specs", and generally I would agree, but I think this may be a different situation. I believe all of the components in the 790 and 419 FEL are rated as components to be useable at far more than the 2050 psi that JD sets the pressure relief on the 790. I believe the lowest rated parts are rated for use to at least 2500psi, but they may all be rated to over 3000psi. All of the hoses and other fittings are rated for use at well over 3000psi. I am not talking about cutting into the safety margin either, I am talking about the recomended safe operating specs.
I believe that JD sets the pressure relief so low on the 790 because their lawyers have run amuck with excessive caution over risks of liability litigation and become convinced that the tractor should not be able to lift enough weight that an unballasted tractor could tip over on a side slope, with the loader at max lift. Rather than tell you you need X amount of ballast if you are going to lift Y pounds, at some slope angle, maybe a safe operating limits chart, JD sells a 30hp tractor is only rated to lift a little over 600 pounds! They set the hydraulic relief valve to a such a low value in an effort to make it very difficult to get in trouble. It's like a "governor" on the throttle of a go-kart track at an amusement park to keep inexperienced drivers from getting in trouble. It isn't that the system can't safely perform better, but they don't want to be responsible if you don't know what you're doing.
The trouble is, some folks get carried away with this and decide if 2500 is nice, 3800 is even better. Then I agree they are asking for trouble, but I have a hard time believing that 2500 psi will cause a problem. JD has just become excessively cautious. I really don't believe this is an issue of overloading components past safe operating limits, but some lawyer's idea of making a "safe" tractor. Those of you who are firearms enthusiasts will recognize this from the talk we've heard about making "safe" guns and "safe" bullets. It is truly a whacky world we live in.
If I add about 1000 pounds of ballast, bringing the tractor over 3000 pounds gross weight. at that point I should be fine picking up considerably more than 600 pounds. I know enough not to be very careful if I lift a max load very high, or on a slope. I am happy to take responsibility for what I do with the tractor and wish the lawyers would stay the heck out of it. Today I tried to lift one end of a 19' steel plate that I've calculated to weigh about 1500 pounds, and I couldn't even lift one end of it six inches. With a completely unballasted tractor, I couldn't even get the back wheels off the ground lifting with the loader. I could just barely unstick the steel plate from the ground and shove it around. I just think that is silly for a 30 hp tractor.
I totally agree. I've never seen any hydraulic components that were rated for less than 2500 max working PSI. I remember reading somewhere on a post here that the part number of the hydraulic pump on the 790 is the same as one of JD's other models that has a higher relief pressure. That being said, I feel safe pumping 2500 PSI to the cylinders. I also know the hoses can handle it. The only part that I don't absolutely "know" can handle 2500 PSI is the SCV, but I tend to think that it's not a problem.
The 790 has a shorter wheel base than some of it's different colored bretheren. Therefore, it is more apt to tip forwards without rear ballast. The low working PSI of the system was JD's way of making a safe tractor. I totally think that 2500 would be fine given you know what you are doing.
I know that it really "woke my tractor up" when I added a pack of shims. The loader is actually able to lift itself out of a pile of rock now....
The 790 has a shorter wheel base than some of it's different colored bretheren. Therefore, it is more apt to tip forwards without rear ballast. The low working PSI of the system was JD's way of making a safe tractor. I totally think that 2500 would be fine given you know what you are doing.
I know that it really "woke my tractor up" when I added a pack of shims. The loader is actually able to lift itself out of a pile of rock now....
JerryG
Super Member
Not to anyone individually. Some of the problem might be with the front axle. I know that is why you can't put the new NH loader on the older TCs.
