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790 HP Reduction By John Deere
- Thread starter Mrwurm
- Start date
- Views: 9344
The rockshaft assembly has the relief valve in it for the entire hydraulic system. That means by increasing the relief pressure there, then you increase the lifting ability of both the three PH and the loader. There is a little cap under the seat that you remove and you add shims to increase the pressure. The shims come in an assorted package (about $2.50). I added two packages worth. The system is set at 2050 PSI from the factory. I'm not sure how much I've increased it by, because I haven't put a guage to it yet, but I don't think it was too much because the relief will not stall the engine at an idle. The loader will now pick the back end of the tractor off of the ground (with fluid in the rear tires). It is now comparable to my brother's New Holland 1720 tractor. Keep in mind that JD would probably void your warranty and there are obvious safety considerations in doing this, but in my opinion it was WELL worth it. I will post more later, including the part numbers for the shims and possibly a picture. It is a very easy modification that only takes about 5 minutes to do. My guess is that I have increased the relief pressure by about 200-300 PSI. That is still within the specs of all hydraulic cylinders that I know of. As stated, I will post more later.
OP
Mrwurm
Veteran Member
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- Jan 20, 2002
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- South East Michigan
- Tractor
- New Holland TC30 Hydro 4x4, Gravely Zero Turn Mower
Mark D, thanks for being a renegade. I don't feel so lonely now. You are sure to hear some disparaging comments about this thread. /forums/images/graemlins/blush.gif I increased the relief pressure to my FEL on my NH by turning a little screw that is part of the valve.
F350Lawman
Gold Member
Thanks, I look foward to the pictures and part #s.
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.
cowboydoc
Super Member
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- Dec 23, 2000
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- JD 8320 MFWD, JD 6415 MFWD, FEL, and cab, John Deere MFWD 4600, John Deere 4020, John Deere 4430, John Deere 455 mower, Deutz, and Gehl 4610 perkins skidsteer
REally what you need to look at is pto hp. On bigger tractors they don't even post anything but pto hp. If you only went from 25 to 24 hp you didn't lose much. Losing 3 hp out of your base doesn't mean anything. It's what you put to the pto that matters.
You can compare two tractors. Say one has 30 hp and 22 hp pto. The other tractor has 27 hp and 24 pto hp. You are going to want the 27 hp and 24 pto hp tractor for sure. This is a common mistake people make when looking at tractors. They pay attention to the full hp and not the pto hp.
You can compare two tractors. Say one has 30 hp and 22 hp pto. The other tractor has 27 hp and 24 pto hp. You are going to want the 27 hp and 24 pto hp tractor for sure. This is a common mistake people make when looking at tractors. They pay attention to the full hp and not the pto hp.
yellowsocks93
Veteran Member
Thats very true Coyboydoc. The nice thing about John Deere is that they actually put out the advertised PTO horsepower.
smilingreen
Silver Member
Ok, WE WANT PICTURES!!!!!! /forums/images/graemlins/cool.gif /forums/images/graemlins/cool.gif /forums/images/graemlins/cool.gif /forums/images/graemlins/cool.gif /forums/images/graemlins/cool.gif
mainetreeman
New member
</font><font color="blue" class="small">( I did a little tweaking on the hydraulic system relief pressure and now it's got some power!!
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Hehe...I did some tweaking on my 790 w/ 70 loader too. I traded it in for a 4710 w/460 loader. Of course it cost me about 15k more than the shims. But I gotta say I really, really, really, like the lift capacity now.....lol Sorry just got my new 4710 and couldn't resist gloating a bit....
My 790 was a great tractor. It did alot of work that it probably wasn't designed to do. Did you know that 790's will start right back up after tipping over?? Don't ask how I know its a long story. But I used my 790 last year to haul out my christmas trees. I have a Christmas Tree Farm. I was towing a 16' equipment trailer with about 50 trees, up and down hills in the snow, and mud. Course I had chains on it but it did the job well. Except the transition from flat to slope was a little unconfortable when the trailer started pushing the tractor around. Thats the main reason I decided to go with a larger heavier tractor....
)</font>
Hehe...I did some tweaking on my 790 w/ 70 loader too. I traded it in for a 4710 w/460 loader. Of course it cost me about 15k more than the shims. But I gotta say I really, really, really, like the lift capacity now.....lol Sorry just got my new 4710 and couldn't resist gloating a bit....
My 790 was a great tractor. It did alot of work that it probably wasn't designed to do. Did you know that 790's will start right back up after tipping over?? Don't ask how I know its a long story. But I used my 790 last year to haul out my christmas trees. I have a Christmas Tree Farm. I was towing a 16' equipment trailer with about 50 trees, up and down hills in the snow, and mud. Course I had chains on it but it did the job well. Except the transition from flat to slope was a little unconfortable when the trailer started pushing the tractor around. Thats the main reason I decided to go with a larger heavier tractor....
JimmyD
Bronze Member
I think JD is now using the engine for the 790 that they put in the 4210. If they didn't do it to save cost they may have done it because of availability. The high demand for the 4310, which is a higher profit unit for them, may have played into their decision. My dealer was not aware of the change until I told him about it.
