Case 1845c drive issue

[Jhgabe]

Hello all new to the forum. I have read several post on similar issues. None I feel are quite the same. Just looking for some good advice. Problem is left side does not wanna go forward has low power. It goes fine in reverse. I have cleaned both office in the tandem pump. I have swapped relief valves and even swapped the spools. Nothing changed I have read on here about swapping lines to the drive motors. I have not done this however for fear of contaminating the other side. I did however swap hoses in the left motor. All this did was reverse left side controls. Does this indicate that left side motor is good and tandem pump is bad?

 

[phil314]

I did however swap hoses in the left motor. All this did was reverse left side controls. Does this indicate that left side motor is good and tandem pump is bad?

If you swapped the hoses on the left motor and it still did not want to go forward - that seems to indicates that it's is the left drive motor and not the pump.

 

[Vetech63]

Pressure checks would be in order. Just the charge pressure at standby and during drive will tell most everything you need to know.

 

[Jhgabe]

Thanks Phil 314 I was hopping it was the motor and not the pump due to $$. Motor was strong in reverse so I was fearing the worst that it was the pump. If I rebuild the motor and flush lines and drain and fill hydraulic tank with new filter would it be ok if it’s just seals leaking in motor?
Thanks vetech63 I checked charge pressure it was low I shimmed charge relief valve with some washers to get it up to spec. I also hooked gauge to left side forward port pressure is good until I push left control lever then pressure drops to like 1000 psi. Also when I hold left lever forward I lose right side. Obviously a major pressure leak just wanted to pick ur all brains if u thought motor or tandem pump. I just an ol farm boy trying to make it on ol junk
The owner showed a receipt where he had case put in a rebuilt pump but said it still wasn’t right

 

[Vetech63]

Hook up your charge pressure gauge and record the pressure in neutral at high engine idle. With the engine still at high idle, stroke each lever individually forward and reverse and record those readings of the charge pressure gauge. Im thinking charge pressure is between 200-300 psi on average. It shouldn't drop any or barely at full stroke on each lever in each direction

 

[Jhgabe]

I did manual says 390 to 415 it was like 300 I shimmed the relief valve with washers got pressure up to about 400 pressure stayed constant when I hit levers very little movement in gauge. Hooked gauge to left side forward port on tandem pump would be like 4500 as soon as I hit forward pressure would be like 1000 then recover quickly once I let off

 

[kshansen]

I have read on here about swapping lines to the drive motors. I have not done this however for fear of contaminating the other side. I did however swap hoses in the left motor. All this did was reverse left side controls. Does this indicate that left side motor is good and tandem pump is bad?

A little clarification. You swapped the lines going to the drive motor on the side that has this problem and now it drives good forward but not reverse? Or does it still drive good in reverse? Just trying to be 199% sure I'm following the description.

 

[Jhgabe]

Yes I swapped lines on drive side that was weak only. When I did it just swapped the controls. When I pushed forward on lever it would go in reverse fine. When I pulled back on left lever it would creep forward but just weak. I am kind of hesitant to swap lines to both motors for fear of bringing contamination to the right side and doubling the work load and cost thanks for replying

 

[Vetech63]

This doesn't sound like a motor problem. Have you checked the reliefs on the pump for that side? There should be 1 for forward and another for reverse. You could swap them and see if the problem moves

 

[Jhgabe]

Yes I did swap the reliefs condition stayed the same. I have gauge hooked to the left forward drive port. I am getting 4500 psi which I assume means the pump is good as soon as I hit lever forward pressure drops to around 1000. Could press be leaking off in drive motor which I feel would be odd because reverse works fine.

 

[Vetech63]

Some drive motors have a shuttle valve. Im not sure about yours. Something isn't making sense here

 

[phil314]

I might be wrong, double check my logic here.

If the motor works in reverse in both cases (when the hose are normal & reverse) this would indicate that the pump is working in both directions.
And since motor forward doesn't work in either case, then this would be a motor problem, not a pump problem.
???

 

[kshansen]

I might be wrong, double check my logic here.

If the motor works in reverse in both cases (when the hose are normal & reverse) this would indicate that the pump is working in both directions.
And since motor forward doesn't work in either case, then this would be a motor problem, not a pump problem.
???

Sounds like it to me too, but would have to dig into everything on the forward side of that motor including as Vetech says any valving in the system.

 

[Vetech63]

Take a pic of the pump and the drive motor and post them here. Your system should be a simple design because of the age of the machine. We can help you troubleshoot the problem but we need to see what type of system this is.

 

[Jhgabe]

Thanks again for all the help and replies Here is sum pics if they not good enough I will take more just let me know.
I was looking at seal kit for motor at L P S
One had Teflon seals one didn’t are the Teflon seals that much better? The yellow plastic thing on the side of pump is cap for my gauge I still have hooked up in toward drive port

 

[Jhgabe]

Some more pics thanks again

 

[Vetech63]

Looks like simple Danfoss gerotor hydraulic motors. The next test would be to remove both of the big hoses on the weak drive side motor and put your gauge in the end of each hose. The pump is a 2 way stroke so the oil will reverse direction depending on swash plate position. 1 hose will pressurized when stroked in one direction where the other is the return…switches direction when you stroke the other direction. You should see the same pressure going both directions but the pressure will switch to the other hose. 2 gauges would be better. The reliefs for both directions are in the pump……..1 for left side forward, 1 for left side reverse, 1 for right side forward, and 1 for right side reverse.

 

[scottwolowich]

Just a tip as well, make sure to note the timing of the motor through the process that vetech has outlined above - which orifice gets pressurized based on the rotation of the shaft. This will be useful if you end up having to take the motor apart because it does have a standard timing. I had this exact motor apart earlier this year, it's quite simple, but I didn't check the timing before disassembly. Of course you can just swap the hoses if you don't know what to set the timing to but it's good to know.

 

[Jhgabe]

Vetech63 thanks for the advice. Do I need to use a tee fitting for the gauge at the motor or can I just dead end the gauge on the line?

 

[Vetech63]

Vetech63 thanks for the advice. Do I need to use a tee fitting for the gauge at the motor or can I just dead end the gauge on the line?

Dead head the gauge in the line to completely eliminate the drive motor