Total noob here trying to understand my tractor

[rScotty]

I actually have a call in to John Deere last night they are looking into the parts for a power beyond for me. I know that's what I want to do long term I was just wondering if maybe there was a way to get it going now in the interim. Let's see what the dealer gets back to me with. Anybody have an idea of what a power beyond kit costs?

Why do you want power beyond? What do you plan to do with it. The flow rate is going to be very low.

Your 790 has an "open center" hydraulic system. In fact, the entire tractor is very similar to the Yanmar YM330 built circa 1980. Same engine, same transmission, same frame, and same hydraulics except for the addition of power steering. That's not surprising, since Yanmar built the 790 for JD. It was a darn good tractor, and Yanmar was able to give the design a second life by rebadging them.

With any luck, your dealer will be able to help. But keep in mind that many JD dealers are not too familiar with the open center hydraulic systems of their old compact tractor line. That may be partly because larger JD tractors use a more complex and unique "closed center" type of hydraulic system that does require special knowledge. And parts for the closed center system are specific to JD and rather expensive. Luckily, that doesn't apply to yours. Those old open center systems like yours are all about the same and there are lots of suppliers for parts.

Since you have a loader, there is a good chance that you already have most of "power beyond" already available. Most loader control valves - the two-lever valve you work with your right hand - have a port built into them where Power Beyond fluid is available. Take a look at yours. See if one of the unused or blocked off ports on the valve body has the initials PB cast into the valve body. Alternately, find the model and maker info off of your loader valve and we can go from there.

The challenge with your system will come about because the limited amount of hydraulic fluid is already being prioritized for the power steering, three point hitch, and the loader - not much left over for PB.
luck,
rScotty

 

[texasranger556]

He said he wants a backhoe. 790 main pump is open center rated at 5.4 GPM, 2050 psi according to tractordata.com. Power steering is rated at 4.2 GPM, and the parts diagram lists two different hydraulic pumps so there are two hydraulic circuits. The 5.4 GPM pump likely supplies the loader then 3 point hitch through the loader valve power beyond port. A factory power beyond kit diverts the loader power beyond port to a quick coupler on the rear of the tractor with a loop hose that normally feeds the 3 point hitch. When a backhoe is mounted, the loop hose is disconnected and the pressure hose of the backhoe is connected instead. The return of the backhoe dumps to tank. In this configuration the 3 point hitch is not usable. The loader and backhoe both see full 5.4 GPM flow. The caveat is you can't use the loader and backhoe simultaneously, which isn't a problem when digging a trench.

5.4 GPM is plenty for a small backhoe. My 4400 is rated for 8.3 and when digging with the backhoe I normally run the engine about half throttle, so probably about 4-5 GPM range.

 

[waygeekierthanu]

Pictures

 

[waygeekierthanu]

He said he wants a backhoe. 790 main pump is open center rated at 5.4 GPM, 2050 psi according to tractordata.com. Power steering is rated at 4.2 GPM, and the parts diagram lists two different hydraulic pumps so there are two hydraulic circuits. The 5.4 GPM pump likely supplies the loader then 3 point hitch through the loader valve power beyond port. A factory power beyond kit diverts the loader power beyond port to a quick coupler on the rear of the tractor with a loop hose that normally feeds the 3 point hitch. When a backhoe is mounted, the loop hose is disconnected and the pressure hose of the backhoe is connected instead. The return of the backhoe dumps to tank. In this configuration the 3 point hitch is not usable. The loader and backhoe both see full 5.4 GPM flow. The caveat is you can't use the loader and backhoe simultaneously, which isn't a problem when digging a trench.

5.4 GPM is plenty for a small backhoe. My 4400 is rated for 8.3 and when digging with the backhoe I normally run the engine about half throttle, so probably about 4-5 GPM range.

Exactly, so you think I need the power beyond right? Quote from dealer was 500 shipped

 

[Peter 315]

To run the JD backhoe you will need the power beyond kit

 

[rScotty]

Exactly, so you think I need the power beyond right? Quote from dealer was 500 shipped

That tractor looks real nice in the Photos, congrats.

There's about half a dozen different ways to get hydraulic pressure flow to outboard implements, but they all cost some money. That is why we all hoped the BH came with a PTO pump system.

Looking at your photos, I see that you already have some nice shaped hard OEM pressure lines and terminations rather than hoses, I'd recommend same as the ranger that you go with the offer from the dealer. At least it is painless and it does preserve those nice hard steel hydraulic lines. With more experience you could probably save a few hundred dollars....but it isn't worth it.
Only downsides I can see to the dealer's offer are slight. One is that without knowing more about the hoe we don't know how fast the 5+ gal/minute will operate the backhoe. It is homebuilt so all bets are off. The other is that by using a plug in power beyond you are letting yourself in for some extra monkey motion required to hook up the backhoe while losing loader functions. I like to reposition my hoe a lot, so that would bother me. But it will work.

I don't know if you also lose 3pt functions when backhoe is on. You don't really need or want 3pt functions with the backhoe mounted, though it might be handy initially just to get the pins to line up while mounting the BH.

Another possibility worth considering is to make up your own PTO-driven hydraulic pump. For that you only need the pump with PTO splined fitting (around $500) Two hoses - one pressure & one return ($75), and a reservoir ($100). Then you have to figure some way to mount the reservoir onto the backhoe frame. Reservoirs are usually mounted under the seat & roughly on the same level as the PTO pump. The PTO pump does have some suction, but it is nicest if you have the reservoir just enough higher than the pump to maintain the prime. Here is a link to some pumps, Tractor Supply Co has a 5 gal res. for under $100.
PTO Pumps | Hydraulic Pumps | Hydraulics | www.surpluscenter.com
rScotty

 

[Peter 315]

You loose the 3 point functions with the backhoe connected there is a metal flat bar that holds the arms up on the rock shaft

 

[waygeekierthanu]

Works!!

 

[Peter 315]

Nice looks good

 

[waygeekierthanu]

I totally cheated, I went to the hydraulic line place and had them make up two hoses. I then simply disconnected the bucket tilt hydraulic lines both of them and use those for the backhoe like with extensions. so I just lock the three-point in place because I don't want it moving, the bucket can still go up and down it just can't tilt. Works for me! I will say though, my first project might have been a little aggressive. This tree stump is a monster! Gosh I love my tractor. Bought it from a neighbor that was moving for 5 grand even with only 80 hours on it. Everything I have now I'm still out less than 7 grand total.