790 lift Capacity

SteveH_CT · Apr 16, 2004

Hi Folks - I can't seem to find the thread that talked in some detail about boosting a 790's lift capacity. A friend of mine recently bought a 790 and they are interested in learning about this modification to the FEL system. If anyone has access to this info I'd appreciate getting pointed in the right direction.

Thanks,

zuiko · Apr 16, 2004

There are shims you can get to boost the capacity. Don't know the part number.

I'm also wondering if you can remove the orfice in the hose to increase the capacity, assuming there is one. With the 990 there is, and the loader capacities are a little less than the same loader on the 4x10 series. I wonder if that's why and if there's a good reason for it besides marketing.

SteveH_CT · Apr 16, 2004

Thanks Zuiko - Now I remember the reference to shims, maybe I'll try a search on that.

I appreciate the information,

Tractors4u · Apr 16, 2004

Here is the beginning of that discussion on 790 pressure modifications by Mark_D. This can be found on page 2 of the link below along with follow up comments.

( 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.
)

790 Shims discussion

SteveH_CT · Apr 16, 2004

As always - Thanks for the help - I'm passing the information on tonight - I'll be interested to see how this works out for them. It seems like such a simple process to boost the system 20%.

Bellville · Apr 16, 2004

Steve, please post the results, it sure seems to have worked well for others.

Thanks

SteveH_CT · Apr 16, 2004

I'll be sure to do that!

Thanks,

harleyx142 · Apr 17, 2004

How sure are we this shim thing is safe? /forums/images/graemlins/confused.gif

RoyJackson · Apr 17, 2004

"How sure are we this shim thing is safe?"

Shimming will increase the operating pressures which will increase lift.
As I'm sure there is a margin of safety built into the hydraulics, a little more pressure shouldn't hurt, but the risk of damage lies strictly on the operator who does the change.

I'm reading that the 419 loader has less lifting capacity then the 70 loader had.

Here's how a dealer explained in to be:

The 419 Loader appears that it will not lift as much as the 70 but they are actually very similar. The Lift height for the 70 was rated at 77" while the lift height for the 419 is 88". The higher a loader progresses through the arc will reduce the lift capacity. Therefore, since the 419 is raising another 11" the lift capacity will be less than the 70 loader at a different lift height.

Loader specs:
JD 70 (77" Lift Height, 755 Lbs. Capacity)
JD 419 Loader (88" Lift Height, 610 Lbs. Capacity)


So, is the 419 loader really less capable then the 70, or are we just looking at the numbers and making certain assumptions?

I've got a #60 loader on my 670. But for those of you 790 owners, what is the lifting capacity at the lowest height(s) on your #70 or 419 loader? What is the breakout force?

zuiko · Apr 17, 2004

I think the biggest risk is damage to the pump if you set the pressure too high. If I was doing this I would see if I could get a hold of a meter to measure the pressure or be conservative about it.