790 - Needs a little more "umph - Got suggestions?

Henry · Feb 23, 2005

790 - Needs a little more \"umph - Got suggestions?

Gentlemen and elightened Tractor Ladies,

I've had my 790 for several years now and really love it. Currently, I use it mostly for mowing and relatively light loader work without any issues.

However, I've got a big driveway project coming up this summer and I'd really like to be able to do some snow plowing work next winter.

While I know that I ought to purchase a box blade for the driveway work and a reversable back-blade for the snow-plowing, I need some adivse on how to improve the performance of the loader and the basic abilities to handle heavier work.......

I need some advise on "umph" upgrades. Here's my initial thoughts & questions:

<ul type="square"> [*]Replace my turf tires with R4's - What are the basic considerations for doing this?
[*]Add a tooth-bar to my loader for the driveway work - Are they easy to install for a do-it-your-selfer?
[*]Adding shims to the hydraulic system scares me - If I do this, am I risking a major failure?
[/list]

Here's a picture of my driveway.

It's about 300 feet long, with a gentle up hill slope. It's gotten badly rutted and needs to be resurfaced (with gravel) and some sloping done to handle the drainage issues.

Jim_Fisher · Feb 24, 2005

Re: 790 - Needs a little more \"umph - Got suggestions?

Henry,

( I need some advise on "umph" upgrades. Here's my initial thoughts & questions:

* Replace my turf tires with R4's - What are the basic considerations for doing this? )

My driveway has a fairly steep hill with a sharp curve about a third of the way up. My tractor, a 4300, weighs about 800 lbs more than your 790. I have a seven foot Meyer snow plow that I modified to mount on my loader in place of the bucket. With two wheel weights per rear tire, a 600 lb ballast box, and a set of standard ladder chains on the rear, traction is rarely an issue. Like you, I have turf tires.

How much ballast (loaded tires, wheel weights, ballast box) do you currently run? You'll need sufficient ballast no matter what type of tire you run.

Aside from the obvious safety factors involved, ballast behind the tractor in the form of a ballast box or heavy implement is especially important when using a loader to carry a heavy load. Without it, you'll place an undue amount of strain on the steering axle which can result in premature seal and bearing failure.

If you're planning to purchase a box blade, you might want to consider using it as ballast while you are using the loader.

( * Add a tooth-bar to my loader for the driveway work - Are they easy to install for a do-it-your-selfer? )

A tooth bar will certainly increase your ability to excavate with your loader. Search the forums for "tooth bar". You'll find lots of information.

( * Adding shims to the hydraulic system scares me - If I do this, am I risking a major failure? )

If the pressure relief valve is set substantially below spec (check it with a pressure gauge), then adding shims to bring it up to spec is certainly acceptable. Adding shims to the relief valve for the purpose of raising the pressure above spec will likely be costly in the long run. The relief valve is there to protect both the hydraulic and mechanical components of the tractor and attachments. Better to make two trips then bend or break something trying to carry a lazy man's load.

_RaT_ · Feb 24, 2005

Re: 790 - Needs a little more \"umph - Got suggestions?

Henry, you really need to look up the internet site that explains how to repair gravel roads. It will help you to figure out what you need and when you need to do it. Working the road when it is dry is not advisable, likewise, a road that is rainsoaked will create problems. Your basically going to need to rip the pot holes which in your case, may be the whole road. For that, you would need a boxscraper, but don't skimp on a light duty or even medium duty if you want some umph. I wish I could remember the site for gravel road repair, perhaps someone will refresh us.

creeper · Feb 24, 2005

Re: 790 - Needs a little more \"umph - Got suggestions?

[You could consider asking the dealer to install some shims and he would be able to check press with a gauge at minimal cost.I installed 1 pack and havn't had any trouble,but can't comment on long term.For implements.... I find you need a variety, as sometimes a blade will work better to move a high crown back to the edges.The box blade works better for loosening the entire drive and re-dragging it.I use a 5' frontier blade on a 790 and really haven't neede more power.The best time to do it is during or after a light rain.

rockyridgefarm · Feb 24, 2005

Re: 790 - Needs a little more \"umph - Got suggestions?

Well, O Great Ratto , is this the link?

Maine camp Road Manual

It sure has helped me!!!

tomrscott · Feb 25, 2005

Re: 790 - Needs a little more \"umph - Got suggestions?

I have added the shims to my system and am ABSOLUTELY convinced it is not a problem.

JD limits the pressure to limit how top-heavy a load you can lift for reasons of stability, and legal liability, NOT because the hydraulic components cannot stand the pressure. I am confident that the system components can all handle well over 3000 psi. I built a peak-reading pressure gauge because I wanted to see what the FEL system was really seeing when you drive into a load of gravel, and use the bucket tilt to pry loose a large load. Even without the shims, your hydraulic cylinders and lines can see 3000+ psi due to these transient stresses that are not powered by the valve spools. In other words, if you have your valve centered, the pressure relief is not active. If you then drop a ton load in the bucket, the hydraulics are going to see the stress. Not all loads are caused by pump power.

I have (well, had... As I've posted pictures, I've been cutting it up into wheel weights and other scrap) a large steel plate that was over 2000 pounds that I needed to move. I couldn't even unstick it from the ground with stock system, felt downright "impotent", but with the shim kit in place, I could lift one end of it about three feet off the ground and managed to drag it by lifting one end and rolling it over firewood rounds. The biggest challenge moving it after the shim kit was the lack of ballast making traction difficult (working on fixing that though).

The shim kit is definitely the way to go.

The next thing I am tempted to do is to replace the lift cylinders with 2" bore cylinders. That way, with no pressure increase you get a large increase in lift capacity. The only concern then is being sure you are lifting straight. At some point the structural rigidity of the loader frame might come into question, but that could be reinforced too for that matter.

In my humble opinion, the pressure relief setting on a stock JD790 is a lawyer-imposed limit that has nothing to do with system strength. The service manual even says something to that effect, that the pressure relief setting is to prevent users from lifting a load that would be unstable for the lightweight tractor. Having said that, you do have a responsibility to get proper ballast on the tractor. It only weighs a little over 2000 pounds and ought to weigh more like 3000 pounds for the horsepower it has. I am adding about a thousand pounds of wheel weights to my R4s because I have a very steep hill to grade and need all the traction I can get, so I am not very worried about lifting a top heavy load.

tomrscott · Feb 25, 2005

Re: 790 - Needs a little more \"umph - Got suggestions?

Also, remember that the shim kit adds no additional stress to your system under normal operation with average work. The only time it has ANY EFFECT is in those rare instances when you are lifting a maximum weight load. The shim kit allows the system to develop about 400 or 500 psi more pressure before the pressure relief valve bypasses the pressure. This is really a very small increase relative to the safety factors in hydraulic components, even if the system were near its design limits to begin with, which it isn't. I think some people envision a system that is always running with increased pressure in the lines as a result of the shim kit, where it might continually accumulate long term stress, but that is just not the case.

If you go to the safety forum you can read about people who have burst steel hydraulic lines, not because they increased the pressure of their system, but because they encountered transient loads while scraping with the scoop down and working a load with the tilt cylinder. The pressure actually encountered during such activity, which you can still experience (even without the shim kit added to a 790) can easily exceed 4000 or 5000 psi if you aren't careful. I have seen in excess of 3000 psi BEFORE adding the shim kit without half trying. The shim kit just allows the system to develop about 2500 psi or so while lifting a load, this is not going to cause premature disaster.

But then I may be full of !@#$%^&*( too!

Sorry, but the lawyers in this world just get my blood boiling.

A lot of people have installed the shim kit with no problems, I have not heard of one documented case of damage that can reasonably be attributed to the installation of a shim kit, just a lot of folks arguing against it on principle. That would be fine if we were talking about a system limit designed by JD engineers and not JD lawyers. /forums/images/graemlins/smirk.gif

Get a shim kit, cheapest performance increase you'll ever get, and will never again worry about. /forums/images/graemlins/wink.gif

RoyJackson · Feb 25, 2005

Re: 790 - Needs a little more \"umph - Got suggestions?

"A lot of people have installed the shim kit with no problems, I have not heard of one documented case of damage that can reasonably be attributed to the installation of a shim kit, just a lot of folks arguing against it on principle."

I installed the shim kit...kit, not kits!

Although I was a bit leery at first, when I went to order them (on the Deere parts website), they were shown installed in the illustrated parts breakdown.
My question (rhetorical) was, "if they're shown in the parts catalog, why aren't they installed by the factory?"

Anyway, I've had them installed for about 6 months with no adverse affect.

If anyone does install the kit (not KITS), there are components that can fall out when the cap is removed (two spacers and an o-ring), so be aware of that.

Henry's original post asked these questions:

Replace my turf tires with R4's - What are the basic considerations for doing this?

You'll probably need the wheels as well as the tires. I had turfs (bar turfs) on my 670. The R-4's on my 790 don't do any more damage to the lawn if you use common sense.

Add a tooth-bar to my loader for the driveway work - Are they easy to install for a do-it-your-selfer?

This is an easy install job. It's going to help a heck of a lot, but it's not going to make your 790 a 10000 lb Industrial Front End Loader

Adding shims to the hydraulic system scares me - If I do this, am I risking a major failure?

Nope...read above (again, this comment assumes a modicum of common sense). However, for most the tasks Henry described, the shims aren't going to help much. It sounds like the biggest bang for the buck for those tasks is more weight for more traction. If Henry goes for the R-4's, he'll definitely want them filled.

By the way, Henry...I'm just SE of York....where abouts in PA are you?

_RaT_ · Feb 25, 2005

Re: 790 - Needs a little more \"umph - Got suggestions?

Also note how much a gauge will spike when you back drag and the bucket hits a rock or when you go forward with the bucket tilted down and do the same, it is one way to break open a line as the forces are huge, but this happens regardless of anyone adding a shim to boost pressure. I have watched my gauge get pegged at 5000 PSI when not carefully back dragging an area with my loader.

Henry · Feb 26, 2005

Re: 790 - Needs a little more \"umph - Got suggestions?

All of you guys provide great advice..... Thanks a bunch. I guess I'll need to do a little more reading about the shims and talk to my local dealer.