743B RH Steer malfunction

[123ignitionusa]

I have a 743B SER#509324953. It has a little over 4000 hrs.
I recently rebuilt the steering and drive motors as a result of the chaincase filling with Hyd oil.
It was working fine until recently, now the right hand stick loses forward power. I get reverse but no forward. Sometimes I can rock the lever back and forth and get it to work.
I have been contemplating the Replenishing valve but hate to just throw money at something. Are the valves serviceable? Does the type of hydraulic fluid make a difference? Any help diagnosing this would be appreciated.

 

[123ignitionusa]

Does this look to be the right part?

 

[123ignitionusa]

What is the difference between this poppet 6513432 from what I see they go into the same place as the high pressure valve above

 

[123ignitionusa]

Hope this helps someone. Problem Solved!
As mentioned I had recently rebuilt my drive motors in March of 2022. By about July the steering malfunction started showing up. I replaced the High pressure replenishing valve thinkin it couldn't be the Drive motor, it was just rebuilt. Wrong! So I contacted LPS (Loader Parts Source) James sent me a pdf of how to isolate the drive motor from the rest of the system. It is called a pump dead head test. The two large caps you need are a JIC12. I bought 4 plugs and 4 caps from Discount Hydraulics Direct (Click the active link) When you do the test the pump should stall the motor. Mine did so I knew the problem was in the drive motor. It is not a difficult job. I found that one of the three o-rings installed in March had disappeared. It is the one in the center with the wide flat retainer ring that covers it. In the kit it is slightly off color. Took about 1.5 hrs start to finish. All is working good.

 

[dfb]

Hope this helps someone. Problem Solved!
As mentioned I had recently rebuilt my drive motors in March of 2022. By about July the steering malfunction started showing up. I replaced the High pressure replenishing valve thinkin it couldn't be the Drive motor, it was just rebuilt. Wrong! So I contacted LPS (Loader Parts Source) James sent me a pdf of how to isolate the drive motor from the rest of the system. It is called a pump dead head test. The two large caps you need are a JIC12. I bought 4 plugs and 4 caps from Discount Hydraulics Direct (Click the active link) When you do the test the pump should stall the motor. Mine did so I knew the problem was in the drive motor. It is not a difficult job. I found that one of the three o-rings installed in March had disappeared. It is the one in the center with the wide flat retainer ring that covers it. In the kit it is slightly off color. Took about 1.5 hrs start to finish. All is working good.

Thanks for the info and update! I had drive problems with my 742B and narrowed it to a motor by swapping the motor side to side. I had a local h
hydraulic shop rebuild the problem motor[All is well} then had them do the 2nd one.....then the problems began. I had a 2nd shop redo the motor and there were seals out of place. It can happen for whatever reason, glad you got it straightened out.

 

[123ignitionusa]

Just wondering what could have caused this o-ring to disappear in the motor. When I did the rebuild originally in March the retainer was cracked and the o-ring was in pieces and partially gone. (Ref 21 and 22) This time the retainer was still there and un harmed but no sign of the 0-ring. Could Hydraulic oil cause the o-ring to break down or something else?

 

[hobbyfarm743B]

Thx for sharing.
My drives were rebuilt and all was working well. The right drive quit and going to have seals replaced again.
Also going to order all new inline filters, fluid change.
Gonna pull engine, clean and replace hard lines under.
Last time drives rebuilt, seals were fragmented or missing. All filters flushed out and new fluid.