repairs for NH-LB-620 backhoe

bullandrambuilders · Jun 29, 2014

Id like to introduce myself and thank you for your time to help me beforehand. I am a builder who is getting into rammed earth construction / compressed earth block masonry methods. I have a new holland lb-620 backhoe that I have been working on that has a couple issues. As of now the backhoe has really strong hydraulics ..the hoe and loader work wonderfully. But I am having issues with the drive propulsion power. It is a shuttle shift machine.

1st- weak propulsion forward and backward. Mainly after the machine runs and gets warmed up. I can move forward and backward but it struggles to get up slightly steeper grades than level.

2nd- I noticed my hydroback/propulsion assembly near the front hydraulic pump off the engine has broke at the bolt I have a pic attached that shows the piece. I am not sure what the hydroback propulsion linkage operates. I assume that would be directly related to my propulsion issue.

Any help will be appreciative. I will monitor the thread to answer any needed info.

Thanks and god bless

Kernopelli · Jun 30, 2014

Looking at the parts diagram for it, it appears that could very well be your problem. Looks like that is the link for F/R drive control and the one on the other side of the pump is what returns it to neutral position. The way it looks, I am surprised you have any F/R drive at all. If you look at the parts diagrams, the cable that comes off the foot control pedal diagram ( #8 CABLE
propulsion, Includes Washer790615 ) is the same cable that snapped on the hydroback unit ( pump drive diagram ( # 13 CABLE propulsion, Includes Washer 790615) Your snapped cable is the cable that links the pedal to the hydroback unit that operates the F/R "propulsion". The 2 diagrams are simply showing each end of the same cable.

BTW....I had a push/pull cable break in a very similar manner. It operates my F/R on my Mitsubishi. New OEM cable was about $300. I could have one custom made for about $75. I decided to simply weld the broken piece back together and would have one made if it didn't work. That's been several years and several hundred hours of F/R shifts ago and it is still working fine.

bullandrambuilders · Jul 1, 2014

Kernopelli said:
Looking at the parts diagram for it, it appears that could very well be your problem. Looks like that is the link for F/R drive control and the one on the other side of the pump is what returns it to neutral position. The way it looks, I am surprised you have any F/R drive at all. If you look at the parts diagrams, the cable that comes off the foot control pedal diagram ( #8 CABLE
propulsion, Includes Washer790615 ) is the same cable that snapped on the hydroback unit ( pump drive diagram ( # 13 CABLE propulsion, Includes Washer 790615) Your snapped cable is the cable that links the pedal to the hydroback unit that operates the F/R "propulsion". The 2 diagrams are simply showing each end of the same cable.

BTW....I had a push/pull cable break in a very similar manner. It operates my F/R on my Mitsubishi. New OEM cable was about $300. I could have one custom made for about $75. I decided to simply weld the broken piece back together and would have one made if it didn't work. That's been several years and several hundred hours of F/R shifts ago and it is still working fine.

So I found a replacement threaded rod that was 1/4in unf threads to fix the hydroback propulsion linkage. And I found the microswitch assembly has two wire coming from it and its free no connections. I am wondering where I should be connecting these two wires from the hydroback microswitch? My manual doesnt go into depth about this wiring.

when I do re attach the hydroback propulsion arm how should it be adjusted so that it is neutral? I assume the arm should press the hydroback cam up slightly to have some tension. Am I wrong?

Mind you my machine I found is actually the original General lb620 and differs slightly in schematics from the new holland version. Same components but things may be flipped or different.

Kernopelli · Jul 2, 2014

I can't really help with specifics on anything. I'm not familiar with your machine. I would say, befor you disassenle the hydroback to repair it, put the broken rod back in place on the hydroback and see how it positioned the neutral control position.

I also assume the microswitch is a neutral safety switch. I have no idea on the wiring but also assume it's been this way since you got the machine, if it's not been an issue, I wouldn't worry about it. There is a wiring diagram on Messick NH parts website.....not sure if it's detailed enough to help but it does show a neutral safety switch that looks like it's wired from the starter relay to a main power leg off the battery.