Mahindra 1538 HST Losing Drive Power

Longtime reader, first time poster. Thanks to the community for all the great info over the years. I couldn稚 decide if this post belongs in the general or Mahindra forums - I知 open to suggestions to move.

I致e a 2015 Mahindra 1538 HST Cab that I bought with 100 hrs on it, and added another 90 hrs over the past couple of years. This is my first tractor, and while I dabble in car and motorcycle maintenance, this is my first hydraulic system besides brake systems.

Over the past several months, it痴 been suffering from a loss of drive power: when I push the forward pedal down slightly, it will move forward very slowly. If I push the pedal further, past maybe ⅓, it loses all drive power and comes to a halt. It happens in L or M gear. In H it can稚 really move at all. It痴 been growing worse (less and less power available) and more frequent (it used to come and go, now it痴 pretty much always happening) all summer.

The engine itself seems to be running fine. I can set the RMP, and it stays right where it痴 set. So, I don稚 think it痴 issues with air, fuel or engine. During this power loss, the front end loader seems to move at its normal speeds, so this loss of power/pressure seems very specific to the transmission.

If I知 on an incline and push in the clutch or put it in neutral, it rolls just fine. Doesn稚 seem to be stuck brakes or something else dragging in the drive-train after the clutch.

The hydraulic fluid level is good, and I致e not found any sign of leaks. I changed all the filters and hydraulic fluid about 80 hrs ago, shortly after buying the tractor used.

Best I can tell, something about the hydraulic system can run slowly (or at low pressure?), but once I ask for more speed something is failing. I知 worried it痴 a dead transmission and that I値l have to have this trailered to the dealer and shell out big bucks. I知 hoping for tips on finding the exact problem, and suggestions on repairs.

The clutch could be slipping. Check the adjustment. But if you have been using it like that all summer the clutch may be too damaged and need replacement.

The other class of problems is hydraulic. If the loader is working normally with a load in it then it's probably not a clogged hydraulic screen or filter. Which would then indicate a damaged HST.

Clutch or HST replacement require splitting the tractor, which you'd probably want the dealer to do.

Check to make sure your rear tires are inflated properly and that the rear rims are not spinning inside the tire. This may seem like a dumb suggestion, but it happens to a lot of people and is often the last thing they would ever suspect or consider. If your rear tires are fluid filled, this exacerbates the problem as it makes the rims nice and slippery and lets the tire bead break loose.

Have you checked the linkage from the pedal to make sure nothing has come loose?

s219 said:

Check to make sure your rear tires are inflated properly and that the rear rims are not spinning inside the tire. This may seem like a dumb suggestion, but it happens to a lot of people and is often the last thing they would ever suspect or consider. If your rear tires are fluid filled, this exacerbates the problem as it makes the rims nice and slippery and lets the tire bead break loose.

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This. I do find it funny that many of us know about this but often it is the last thing we suggest. It should be first thing to check. Good job s219!

K5lwq said:

This. I do find it funny that many of us know about this but often it is the last thing we suggest. It should be first thing to check. Good job s219!

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I seem to recall a thread where someone was doing mechanical disassembly of the driveline looking for something stripped/slipping when the real problem was the tires slipping. It would probably be my inclination as well, if I hadn't seen so many slipping tire reports here on TBN. We often overlook the simple factors.

You can eliminate tire slippage quickly by observation on firm ground. I assume your doing your power evaluation in either low or mid range. Double check to insure brakes are not engaged. Check your forward pedal linkage, as your foot movement may not be conveyed to the accelerator by linkage out of adjustment.

Is there any possibility that air is entrapped in the system? You said you got the tractor with 100 hours on it and then changed the Hydraulic fluid. You then ran the tractor for some hours and slowly this problem creeped in. Is it possible there is air entrapped?

I didn't know about the tire business and I not suggesting that it is not the problem. But if you eliminate the tire issue, then what?

Someone mentioned a slipping clutch..

I am wondering what would happen if there was entrapped air in the system.

What filters did you use when you changed the hydraulic fluid? Some aftermarket filters have been known to cause problems. It may be worth paying for the OEM ones to eliminate this as a potential problem.

Thank you for all the quick responses. I didn't get a chance to go work on it until tonight.

ericm979 said:

The clutch could be slipping. Check the adjustment. But if you have been using it like that all summer the clutch may be too damaged and need replacement.

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I'm afraid you may be right. I tried adjusting the clutch pedal, but it didn't help. In fact, after making an adjustment I went to test things and, again, the tractor moved slowly forward but stopped moving once I pressed the drive pedal past maybe 1/3. I raised the engine's RPM and tried again. I didn't hear or feel anything let go, but after raising the RPM it wouldn't move at all. I lowered the RPM, and still nothing.

Something has changed, and now my tractor won't move at all. High or low RPM, minimal or max drive pedal position. I've adjusted the clutch pedal back to where I found it, but nothing. I tried adjusting the clutch pedal to the max (in either direction, just to be sure), and it didn't make a difference. Besides the clutch pedal adjustment, is there a clutch pressure adjustment I can make? Nothing in the owner's manual about that, only a pedal adjustment.

It's acting like the clutch is fully depressed, all the time. Even without touching the clutch pedal, I can freely shift between L, M, H. No resistance, no sound of grinding gears. It sounds like the mid and rear PTO's won't spin either, but the PTO levers freely move into place. I'm certainly open to the (sad) idea that I've burned up the clutch, but wouldn't I have smelled the clutch burning at some point?

As for other possibilities:

• the tires are definitely not spinning on the rims.
• the brakes are definitely not on. I can get out and push the tractor and it'll roll on the level concrete floor.
• I checked the drive pedal linkage, and it all looks normal to me. No loose or seized pivots that I can see, return springs look to all be in place. Things look to rotate properly up until I see a control shaft disappear toward the center of the tractor. I can't easily get under the tractor to take a close look from the bottom because the belly mower is on, and I can't get it off while the tractor won't move. I also can't pull the mower out sideways because my garage is too narrow for that.
• air could certainly be trapped in the hydraulic system, somewhere. Do you have suggestions on how to diagnose or fix that? The FEL still runs great, moving with the speeds I'd expect at high and low engine RPM. This makes me think it's not hydraulics.
• I used OEM filters from my local dealer when I changed the hydraulic fluid and filters.