Serious RK37SC Hydraulic System Questions

[timebak]

My RK37 is the Shuttle Shift version, and the FEL hydraulics are sloooooow. After adjusting the flow control knob, below the front of the seat, to what is a good speed for lowering the loader, it takes 8 to 10 seconds to dump the bucket, even heaped with chert or gravel and everything warmed up good. Open the valve some more and you can get the bucket to dump in about 5 seconds, but the loader falls out of the sky like a crashing plane. And the 3-pt hitch lift controls are, by far, the worst I've ever experienced in 60 years of running tractors. My tractor has 30 hours on it. And, I've checked all hoses for kinks and pinches, and there aren't any leaks.

First: What is the actual PROPER fluid that goes into the port (with the yellow cap) on the rear of the tractor to the upper left of the PTO shaft that then shows up on the sight glass to the lower right of the PTO shaft??

The operator's manual says that is "transmission fluid" and in at least two places specifies "THF 80W (API GL-4 Grade, Gear Oil 80W)". HOWEVER, the dealer says that's where you put in the hydraulic fluid and it takes J20C hydraulic fluid. So, which is correct?? If that is NOT the hydraulic fluid fill port, then where IS it? These are two vastly different fluids, and the wrong choice will ruin the tractor. The manual has no reference anywhere to true hydraulic fluid.

Second: When raising implements attached to the 3-pt hitch, all of the lift happens in the last three-quarters of an inch of the lift handle's travel, and it's extremely abrupt and jerky, to say the least. Is this normal for these tractors???

At that point, the handle (called the "position lever" in the manual) is all the way to the rear and is very difficult to control. It makes controling a rear blade, box blade, or anything requiring height or depth control exceedingly difficult, if not impossible.

Thanks,
Tim

 

[DonRybak]

Tim, I have to admit that the manual leaves me confused too. From the way I read your manual the shuttle shift uses the same fluid for the transmission and hydraulics as the hydrostatic does. I can't find anywhere that they are separate systems. If they are the same as my hydrostatic then both systems use what they call trans/hydraulic oil. It's clear rather than red like hydraulic fluid. That was an RK mechanic that told you they were different? As far as the knob in front of the seat, I thought that only controlled the speed of the 3 point. Good luck on finding the correct answer......Don

 

[dusty3030]

Something is plumbed wrong. The three point hitch (rockshaft) adjustment shouldn't affect on the FEL valve at all.
I'm not an RK owner but I promise what your tractor is doing is not what it was intended to do. Neither the FEL or the position lever for your three point hitch. Something is plumbed wrong.

Yes, the transmission oil and hydraulic oil are one in the same. Think of the transmission itself as the hydraulic tank / sump.

Your tractor is an open center hydraulic system. Everything other than power steering is plumbed in a series. The power steering is the only standalone.

The hydraulic pump is running when the engine is running. It will suck fluid out of the sump (bottom of transmission housing) and pump it first to the FEL valve, then to any rear remote hydraulic valves you might have, and lastly to the three point hitch (position control) valve.

Your FEL valve should have one line coming in straight from the hydraulic pump. It will have 4 lines going out to the FEL cylinders (two control the lift / lower and two control the curl / dump). It should have one line coming out that dumps non pressurized fluid directly into the top of the transmission somewhere (tank port) and a power beyond line that caries the pressurized fluid to the next valve in the series. If you have rear remotes it will be your rear remote if not it will go directly to the rockshaft control valve for your three point.

The rate of drop for the FEL should be controlled only by the FEL control valve.

 

[dusty3030]

Had some more time and looked up some stuff on your tractor.
From what I read you have a position control for your three point but no draft control right beside it correct?
You also have one set of rear remotes standard correct?

I've been trying to think through your loader symptoms and I'm wondering did they omit the tank line on your loader valve or did they plumb it to the wrong place. You have to have a non pressurized line from the valve back to the sump to have a place for fluid to go for certain parts of the valves function. Example, when you lower the loader you are allowing pressurized fluid to enter one side of the cylinders, but the fluid in the other side has to have somewhere to go and that is the tank port. For the most part gravity is lowering the loader when you have it up in the air and you move your joystick forward. Normal operation is you don't have to press it forward very far to get it to lower then when its on the ground if you push it further you are putting the fluid in under more pressure and it will actually lift the front of the tractor off the ground. Pressing the stick forward opens up the valve to put pressurized fluid into the cylinder. The further you push it the faster it goes down. There is no restriction to the fluid that is being pushed out of the other side of the cylinder it should have a non pressurized non restricted path back to the sump. Same for your bucket cylinders. The rate of drop adjustment for your three point should have absolutely nothing at all to do with the loader function.

 

[DonRybak]

Timebak, did you ever come up with a solution to the FEL issue?

 

[LS Tractor Owner]

Check to see if one of the remote levers is in "detent" position. If one of the remotes is dead-heading, it will affect the loader hydraulic operation as you described.

Make sure all the hydraulic levers are centered.

 

[timebak]

Timebak, did you ever come up with a solution to the FEL issue?

Check to see if one of the remote levers is in "detent" position. If one of the remotes is dead-heading, it will affect the loader hydraulic operation as you described.

Make sure all the hydraulic levers are centered.

Ok, Took it back to the dealer (local RK store). The tractor manager was brand new to RK, but has about 30 yrs in the Ag equipment business, and is like a pit bull after a ham bone when tracking down a problem.

First thing we did was check all levers to make sure they were centered. I found the little lever that controls the rear remote ports (the lever behind the right rear corner of the seat, next to the floor) wedged over all the way in one direction by a ball of plastic wrap jammed down in the slot where the lever travels and part of the floor mat corner was wadded up in the slot behind the lever also. I had noticed in the past that the lever didn't move, but didn't check it out or give it any further thought because I wasn't using it.

So, we fixed that and all hydraulics ran a LOT better. But he wanted to check things further, and kept the tractor overnight so he could talk to one of the national or regional troubleshooter service specialists. After talking to that guy, they re-routed at least one hose and changed the angles of some of the 90 degree hose end connectors. Plus, I could see where they had added Ty-wraps in some places and removed them in others. The FEL worked noticably better.

The other important thing he learned from the regional guy and then showed me is that the 3pt hitch position control system has about 10, maybe 20, distinct positions. You move the lever a little and nothing much happens, but move it a little more and the hitch will move up or down precisely about an inch or so (didn't measure it), and will maintain that position with no drift.

I didn't think I liked the idea of that. But after using it quite a bit over the past couple of months, I like it a whole lot. It makes maintaining a consistent depth of cut or height much easier.

In addition, we learned that the proper transmission fluid for sure is the Providence Premium J20C Trans Hydraulic Fluid.

 

[sengli]

My is slow as well. Had a bobcat tractor before this and it was worlds faster than this one on the hydraulics.