juniur

Member
I've got an 8630 w/ dual power. The problem is the dual power is not shifting. I have checked the floor switch and it's working properly. When I pressure test the low pressure system I have 200-250 depending on engine speed. And when you hit the floor switch the pressure changes ( momentarily drops then returns) which would make me think the control valve is working. However there is no difference in ground speed or the slight" jerk" that you normally feel when one shift. Do you have any suggestions on where to look next?
 
Hmmmm...very interesting. Are you certain the pressure oscillates every time you hit the switch - you've done this multiple times? Does the pressure always come back up to the exact same number every time? I ask this because in normal operation, it is typical to see a few PSI drop when shifting from low to high, and then vice versa when shifting from high to low. This is because the direct drive clutch pack (high) has some normal internal leakage that the underdrive (low) clutch does not.

If the pressures always come back to the exact same number every time you shift, then I'm thinking something is wrong with the solenoid valve. Somehow it's starting the shift process, but can't complete it, so it reverts back to where it started.

I'd also suggest verifying the electrical portion of this by checking current flow with an amp clamp or ammeter to make certain that you have current flow to that solenoid when you're in high range. Just because the lights on the dash change from turtle to rabbit does not mean the solenoid is actually being energized, although the gauge flicker would seem to indicate that it is. Just because you have voltage going to the solenoid, it does not necessarily mean that you have current flow.


One more thing: Can you kill the engine with the brakes in BOTH ranges?
 

Couldn't be simply wear of the sealing rings and the sleeve that they ride in? The flow through the control valve will keep the direct drive engaged even though there is leak by, until suddenly the leakage is too much. I assume that it stays in under drive.
 
Bern,
Your theory about starting the shift process but not completing it is what I'm thinking also. I replaced the control valve and solenoid and got the same results. So then I bench tested both control valves. Mounted it upside down in a vice. Removed the end cap so I could see spool movement. Put air into the port that the solenoid controls. With out power the spool moves and when energized the spool doesn't move. And I realize that air isn't the same as oil but it does verify operation of the solenoid and spool movement.
As far as your question about stalling in both ranges I can't get it to shift out of under drive, so I can not do a stall test in both ranges.
My theory is the direct drive oil port is blocked and not allowing the shift, causing there not to be enough difference in pressure on one side of the spool so it doesn't move completely. But that's just a theory.
 
If we assume for a moment that the solenoid is good (because you tried another one and got the exact same results), then I'm leaning towards an electrical issue. I suspect that, even though the turtle and rabbit lights are switching on the dash every time you push the button, you have an open circuit somewhere before the solenoid, preventing its operation.

As I said in my last post, get a small amp clamp or an ammeter, and check for CURRENT flow in the wire going to the DP solenoid. If you use an ammeter, you'll need to break the circuit and insert the ammeter in series. You should see current flow (likely an amp or two) with the DP in high range, and none in low range. I really do think this is an electrical issue, such as maybe an open circuit in a cab connector somewhere.

If the above tests check out, maybe it's slipping just enough in high range to give you the illusion that it's not shifting. This is why I asked in my last post if you could stall the engine with the brakes. Get the tractor rolling with the transmission in 5th or 6th gear, run it at about 1800 RPM or so, and drag the brakes until the engine almost dies. Do this is both ranges. Do you get the same result? If you do, it's got to be an electrical problem in my mind. On the other hand, if you get a difference in the two ranges, then you have a mechanical issue inside the DP, assuming your pressure stays high in that range.

One more thing that I asked in my last post, is the pressure EXACTLY the same in both ranges? It shouldn't be. High range is generally 2-3 PSI less than low range, in normal operation. Note that I'm not talking about the dip in pressure during a shift, I'm talking about what the pressure stabilizes at after a shift is made.
 
Another question.... are you using a manual gauge for testing or an electric gauge? If you're using an electric gauge, other electrical load variations may cause a dip/spike in the gauge that causes you to think it is shifting...
I tend to agree with Bern that you likely have an electric issue somewhere. I find it hard to believe that there is a scenario where you would have firm drive in both ranges and maintain operating pressure.... unless perhaps the direct drive plates have completely delaminated. That will be an ugly mess to clean up if they have.

Rod
 
I did the current test initially when I began checking it and with an amp clamp hooked to my scope I'm showing 1.5 amps when energized. The instrument cluster doesn't work so no rabbit and turtle light. Power to solenoid or no power is verified by test light I hooked into the circuit.
I just took the control valve off again. There are 4 oil passages in the side of the DP housing. Putting air in 3 of them I hear them leaking internally. The 4th passage is restricted as I get blow back when I release the air pressure.
And as I said the tractor will stall with the brakes but since it's not shifting you can't check both ranges.
 
Ok. I fished a piece of wire down the hole that was blocked and got the passage clear. Put everything back together and the dual power works.
 
Brake material is my guess. Right side was repaired recently. Correct me if I'm wrong but I don't remember anything other than a suction screen on the low pressure side of that system. But you're right it would have had to travel through a lot of places to get there. I wonder if it was an accumulation of fine particles.
 
That screen was only installed at the factory for a certain number of years ( I think). Either way this tractor doesn't have one.
 

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