790 HP Reduction By John Deere

F350Lawman · Oct 16, 2003

The part number for the shims is AM875169. I believe the is the number. There is another number on the package (20030213DY4), but I think the first one is the part number. You need to order two of these packages. It is an assorted pack of shims that you can put in to increase the relief pressure. I first used one package, but that didn't seem to increase it very much, so I used two full packages. This really did the trick. Before my loader was so weak that it wouldn't pick up a full bucket of sand. Now it is just right. I will attempt to get some pics to post on here soon.

Just got a call today, the dealer has my shims. I need photos and some instructions. Please /forums/images/graemlins/smirk.gif

Whiskey · Oct 16, 2003

Scott:

I'm waiting to see if your's blows up before I try.. /forums/images/graemlins/smirk.gif
keep me posted, and I'm going to try the front wheel swap this weekend like I read somewhere you did, I'll see if I can get through it with all my fingers intact.. /forums/images/graemlins/blush.gif

What did you have to give for the parts....and did the dealer give you a "and what do you need these for" question????

Whiskey

Mark_D · Oct 20, 2003

OK, I'm going to try and post a picture with this email. Flip up the seat on your tractor and this is what you will see. You will notice there are three caps. The one on the right is where you will add the shims. Be careful when removing the cap because there are a couple of parts from inside the cap that can fall down and get lost. The shims get added to the inside of the cap, so as to push all of the other parts down slightly more. I originally said to add two full packages, but don't do this. I put mine on a guage and the PSI was way too high. Get a guage, start with one full package, and then work up from there. Keep in mind that the factory setting is 2050 PSI. I have mine at 2500 now with a modest increase in power. (3500 works really good, but don't ask how I know). When putting the cap back on, if it seems difficult, then reach in the hole and pull out the rubber o-ring and slip it over the threads on the cap. I will thread right in then.

F350Lawman · Oct 20, 2003

What reading did you get with one pack and how much extra lift do you think you got??

If hypothetically I did this, I think I'd like the results. I am curious what my hypothetical pressure might be.

Having it run at 3500lbs. and not blow indicates the built in safety factor and makes me feel much better about running at perhaps 2300-2500 for example. I think the hoses are rated for 3000 so 3500 sounds EXTREME but 2500 seem like a good compromise.

Mark_D · Oct 20, 2003

I didn't measure it w/just one pack. I had both packs in when I saw the 3500 (actually a little more...the guage was a 3500 psi guage). My brother, who is a diesel mechanic, said that there was danger of cracking the pump at that pressure. We took out part of one of the packs and came up w/2500. Most of the difference was in the second pack. I would buy two packs (they are very cheap) and add them accordingly. The factory rated 2050 psi is just a safety measure that JD has built into these tractors so that no one turns one over. The frame on the loader as well as the hydraulics are capable of much more than this. I would actually feel comfortable at 3000 PSI....2500 is very well within the safety margin. There is a modest increase in lift capacity w/2500. My tractor would not even pick up a full bucket of sand before.

F350Lawman · Oct 20, 2003

I am happy with the one pack right now. If I had a guage I might be more "adventerous" /forums/images/graemlins/smirk.gif

thanks for the idea and advice.

glalonde · Oct 23, 2003

Being new to this, I would rather not do this blindly but instead rely on a gauge.
Where do you connect this gauge and are they expensive (or can you rent them ) ?

Mark_D · Oct 23, 2003

You just need a guage with a fitting that will fit into one of your FEL hookups. You could probably borrow one if you know a mechanic.

mountain_man · Oct 23, 2003

Mark - Thanks for posting the modification which I'm considering for my 2000 790 (well past warranty). What issues should I be aware of /forums/images/graemlins/confused.gif. I'm guessing the potential for a burst hose, but what about bending something or the effect on the hydraulic pump? Also what effect does it have on the 3ph? Any thoughts?

Mark_D · Oct 24, 2003

If you go with a modest modification (I would say under 3000 PSI) you should have no problems. As stated, before I checked mine with a guage, I was operating at a little over 3500 PSI. It worked great, but at that pressure there was a chance of damaging the pump. Keep in mind the setting from the factory is 2050 PSI. You probably have the 70 loader on yours...mine has the newer 419 loader. If you went to 2500 PSI, in my eyes you have absolutely nothing to lose, only some lift power to gain. I believe that the reason they are "turned down" so much from the factory is for liability reasons. The more lift you have, the more inherent is the risk of tipping the tractor over. I feel comfortable with this and I use counterweight when necessary, stay off of hills, and always keep the bucket low to the ground. Does that answer your question? I don't think your tractor would give you any problems.

Also, the 3PH lift will be increased as well. The relief is for the whole system. It's exactly what the tractor needs.

Mark