John Deere 35G Auxiliary Hydraulic Pressure Test / Adjustment for Thumb

[OptimizedPrime]

Hi all, I have a new to me 2014 JD 35G excavator and could really use some help. I put on a new thumb and it goes down when I turn the mini-ex on but it does not come back up with the stick controls. That leads me to believe I need to adjust my aux. hydraulic pressure either up or down (any insight?). Looking at the service manual (TM12891), I don't know whether I need to adjust the size H6 screw on one side (and which one) or both sides.

I can reach the adjustment screw on the #137 (pink link in bottom pic) but the #136 (purple) is almost impossible to get to and I have lifted the cab.

Do I adjust the pressure somewhere else or is this it? Any help would be appreciated. Thanks!

 

[mg2361]

Is your diverter valve set to two-way flow?

 

[OptimizedPrime]

Thanks @mg2361 for the reply and I appreciate the question, I've seen you help in other similar threads during my search. I do have the two-way flow set correctly and the thumb will not return.

I guess my question is, do I only need to adjust the auxiliary circuit reliefs (136, 137) for the correct pressure or do I adjust the main relief? If just the aux reliefs, how does one know which side to adjust?

 

[mg2361]

Factory settings of those reliefs are set higher than what the thumb is supposed to operate at. Are you sure it is working electrically?

The thumb "is" working in one direction? It will go over relief at the end of the stroke?

 

[OptimizedPrime]

@mg2361 Yes sir, I can put it into one-way mode > lift the thumb manually > put into two-way > start the excavator and it will push itself down.

Electrically, when I use pilot control Left and Right switch I can see the lines jump and hear the pump, it's less to non-existant when I try to raise the thumb.

Part of me thinks I may have to swap the cylinder or lines around. From the cab, the short hydraulic line on the right leads to the input near the cylinder mount to the boom. The longer line is installed on the fitting near the part that extends. This is how it looks installed.

 

[mg2361]

If it is moving on its own, I would suspect an issue with the auxiliary spool.

If you swap the lines at the cylinder and it moves the opposite direction when the engine starts, then you would have a spool that is stuck, or, one of the auxiliary solenoids are leaking moving the spool.

when I use pilot control Left and Right switch

You have a roller switch and are using that , correct?

 

[455c-driver]

This information compiled for reducing the clamping pressure on the thumb close to permit the bucket to override the thumb close circuit but may be helpful for your situation. The diagram number references are to the parts catalog diagrams for the relief valve manifold.

In this setup the piston side of the aux cylinder is on the right side of the boom when looking out from the cab. In that case, adjustment nut 136 is the setting for the thumb opening. 137 is for thumb closing and is accessible without tilting the cab by removing the small panel where the selector block for the aux mode is.

"

If the selector block is at 9 o’clock then you are in two-way flow mode or clam mode (snapshot from operator’s manual). In two-way flow mode (at 9 o’clock) flow is then sent thru line 37 that connects to the left side of the relief valve manifold. In two-way flow mode line 37 is in the circuit and pressurizes line 40. Therefore line 39 that connects to the right side of the relief valve manifold is not in the control valve circuit and is always on and in breaker mode is the only line pressurized. And line 39 connects to the auxiliary block on the left side of the stick. And line 40 connects to the auxiliary block on the right side of the stick. And line 40 (via selector block at 9 o’clock) connects to line 37 that connects to the left side of the relief valve manifold. Therefore relief pressure adjustments for line 40 are made for the auxiliary block on the right side of the stick. The right side auxiliary block is the test port side for line 40. And left side of valve no. 5 counting in from the blade side is the relief valve that is adjusted for line 40 relief pressure. Per operator’s manual (2-3-10) moving auxiliary switch left operates the hydraulic breaker. Because the hydraulic breaker is always on, switch left must pressurize line 39 that connects to the auxiliary block on the left side of the stick and that connects to the right side of the relief valve manifold. Therefore moving auxiliary switch right must operate the right side auxiliary block. And line 40 connects to the auxiliary block on the right side of the stick. And line 40 connects to line 37 that connects to the left side of the relief valve manifold. By field test, the thumb currently closes when the auxiliary switch is moved right. The right side hose connected to the right side auxiliary block is the piston side of the thumb cylinder. Field test confirms that auxiliary to the right pressurizes the right side auxiliary block connected to line 40 that connects to line 37 that connects to the left side of the relief valve manifold. Therefore adjust left side of valve no. 5 counting in from the blade side." ​

"The left side of the relief valve manifold is accessible by removing the access panel that covers the aux line selector.
"