2018 Mahindra HST 2555 Forward & Reverse Issues

[DWD Farms]

In late May of this year (2020) I bought a 2018 Mahindra 2555 HST with 264 hours on it. From the dealership it seemed to be a solid machine. With the tractor I bought a grapple so it took a couple of weeks to get that in and rigged out. I finally got the tractor to the farm to put it to work. Within the first two hours I started to have issues with forward and reverse, the tractor wouldn稚 go or would buck in either direction. Called the dealership and they said to check the two plugs on the right side under the floor board to see if they had water in them, we had a major down pour and the tractor was setting out in it. I got an air hose and blew out the plugs, replaced, and all was fine for the rest of that day, the very next day same thing. I repeated the procedure but this time it didn稚 change, the tractor still had moving issues. Loaded it up and took it back, after a couple of weeks they finally replaced the main HST module. Now the tractor has 304 hours on it and I am having the exact same issue. I cleaned the floor board plugs again and again the tractor ran all afternoon with no more issues, went out two days later and didn稚 get 400 yards when it stopped, wouldn稚 go forward or reverse. Took me a good 30 minutes to get it back to the barn. The warrantee has ran out and was the first time but because I had just bought the tractor they covered it. I don稚 think the HST module has gone bad again and now not sure if that was the issue in the first place. Any advice or help would be much appreciated. I really don稚 have time to let the tractor set in a shop.

 

[Reb954]

What are you blowing out of the plugs? If it is debris and/or water then change the oil and filters.

 

[DWD Farms]

Honestly I can't see anything. The plugs look clean and dry each time. I have even taken a shop towel to each end attempting to see if I can see any moisture. As of last night I bought some automotive electrical contact cleaner, opened up each plug and sprayed. Let that dry then replaced each one. I ran the tractor about 30 minutes with no issues.

 

[Reb954]

I don't have an HST and haven't been around one so I am shooting in the dark here but comparing it to an automatic transmission I would check the oil for a burnt smell to see if the transmission has been over heated. I would also change the oil, filters and clean any screens for the transmission. Beyond that, I don't know what to suggest.

 

[DWD Farms]

I am willing to try anything. I think the tractor is driven from the hydraulic system on the HST models. I can and will change filters and fluid

 

[Reb954]

Thinking more about it, I wasn't sure what you meant by plugs but in thinking it out you probably mean electrical plugs. With that in mind, add some dielectric grease to the plugs to help keep moisture out. Then following the wiring to find any other plugs that may need cleaned out and add the dielectric grease to them. The moisture could even be in the mechanisms operated by the foot pedals.

 

[DWD Farms]

You are correct, my bad for not being more clear. It is the electrical connections for the forward and reverse pedals. I have traced the harness and both go to the main HST module the best I can tell, those wires from each go into a larger bundle and head toward the front of the tractor which has two very large plugs, each have maybe 30 connectors (didn't count but it is large number), I pulled those plugs also but they look spotless but they should as that module was replaced by the dealership less than 50 hours back. I have tried to take notice of conditions like how long has the tractor been running, how hot is it, how humid is it, (Arkansas) what type of work am I doing with the machine but can't really tie any specific thing to the issue. I haven't applied any type of conductivity grease but again willing to try anything.

 

[mikeman1]

I put dielectric grease in all connections i could take apart and zip tied together so they wouldnt slip apart when i bought my 2555 new. now it has about 270 hours on it. all seems good. I also let mine sleep in the barn.

 

[DWD Farms]

I did that after the dealership put the new HST module on it in June, that was at 260 hours and the tractor made it to 300 before the next hick up. The last thing I tried was to clean out the dielectric grease the best I could and sprayed electrical contact cleaner on all the connectors both under the floorboard and on the new module. I have only put a few hours on it after that so to early to see if that has made any difference. It now stays under the shed out of the direct rains.

 

[DirtHauler]

Along with your grapple. did you buy an after market 3rd function valve (ie. W.R. Long) ?

 

[DWD Farms]

The grapple is a Mahindra brand. The third function valve has not one indication of manufacture so I just assumed it was built third party and sold to Mahindra.

 

[DWD Farms]

Now i have another potential issue. Running the brush hog on Saturday. Some of the meadow was a little thick, when I got to the thicker stuff the hog would wind down and even almost completely stop, I would have to lift the hog let it take off again. The question/issue, when the hog would do this i wouldn't notice any change in the engine tone like it wasn't putting a load on the engine at all. Running in low range at about 2200 RPM. Should I notice a load on the engine ??. With the the whole machine being hydrostat I don't know if this is normal or not.

 

[mikeman1]

Couple things come to mind, does yours have the load sensing switch on the dash? that might have something to do with it.
or if you have slip clutch on hog it might be too loose. but be careful if too tight you could break the gear box or pto shaft on your tractor. I hit a tire in the field with mine few weeks back and luckily the clutch on teh hog slipped, enough to make it smoke until i shut off the pto , pulled away and it cleared the tire and all was fine.

 

[LouNY]

If someone had the hydraulic schematic for your tractor it would be helpfull.
This thread in addition to your other makes me lean more to your tractor hydraulics.
If your pump is not maintaining good flow for your pto system and possible for the charge line of the hydrostatic pump it would explain many things.

What many people do not realize is that with your hydrostatic transmission you often have an external pump that provides makeup fluid for the hydrostatic drive which is a closed loop system.
Many times your tractor will have a pair of engine driven pump one of which is for your remotes and loader and a smaller one piggy backed to it which provides the fluid and pressure for hydraulic controls such as pto and steering as well as the makeup or charge line for the hydrostatic drive.

 

[DWD Farms]

I do have the load sensing button but haven't ever used it. The way I understand that is that is slows the travel speed as the tractor loads. In this case the motor never changes or loses RPM but the hog will completely stop, was out this evening and had the same issue like I thought it would fix itself. Also, my other issue came back on the travel, the tractor would just stop like I had taken my foot off the petal, the F light would blink as the tractor bucked. Took it to the barn sprayed the F & R electrical connectors again under the floor board and all was fine with the movement. It did seem as the tractor got up to full temperature through out the machine the less power the PTO had. Seems to lean toward the clutch assembly in the housing. Looks like a trip back to the dealership.....

 

[DWD Farms]

New issue, I am now told that I have a bad potentiometer. It is stuck with the forward light on so I can't even start the thing. Anyone ever replaced one and if so where can I find instructions for calibration after replacement.

 

[mikegatherall]

New issue, I am now told that I have a bad potentiometer. It is stuck with the forward light on so I can't even start the thing. Anyone ever replaced one and if so where can I find instructions for calibration after replacement.

Ours had some room for adjustment - mounting holes are ovaled.