Cub Cadet 129 won't move after sitting

wilypence · #1 01-30-2023, 08:21 PM

The Cub Cadet fever bit me again and I ended up with a 126 and 129 that I was able to get working. The 129 is my first hydro Cub, and well, the jury is still out if I prefer gear drive or this hydro.

I don't know the history on the 129, but it seemed like it was restored maybe 15 years ago and then it just sat unused. I rigged it to just see if I could get it running, and after that was successful I went through all the normal maintenance items on the engine: carburetor, fuel lines, ignition system, battery, oil, and going through all the maintenance items. It fired right up and everything worked 100% except for it was leaking hydraulic fluid pretty heavy, it turns out from the relief valves.

When I bought it the tunnel cover was missing which I was afraid was a bad sign. I replaced the hydro fan based on feedback from this forum since all the blades were broken off. While I had the driveshaft out I went ahead and replaced the flex disc and hub. I sent the relief valves to MachTech and after replacing those, pulling the rear cover, and replacing the fluid and filter, everything worked great and it hasn't leaked a drop of hydraulic fluid since. Over winter break I ran it all over the yard in forward and reverse and the hydro worked fantastic at all engine speeds. It never missed a beat since I serviced it and had the relief valves fixed.

However, it sat for about 2 weeks or so without being run. When I fired it up to mow the other day, it would not move in reverse or forward at all. I checked the normal things, making sure the hydraulic fluid was topped off, checking to make sure I could see the driveshaft on the output of the hydraulic pump was turning, etc. I pulled the relief valves and they look fine and free of debris. I even tried pouring some hydraulic fluid down those 2 holes where the relief valves install, and even tried some compressed air in the fill hole thinking the pump just wasn't priming. Still no movement at all, and I don't even notice any noises when I try and go forward or reverse. Someone converted it to foot control, and I confirmed the linkage is operating the lever going into the hydro unit properly when I work it through the range of motion. I pushed it (relief valves are the auto release style) a good 30 yards to see if that would help prime the pump.

The only thing I haven't tried is to pull the new filter I installed to see if it was blocked. When I originally pulled the rear cover the unit was actually very clean with no major debris in the bottom of the rear axle housing. I carefully wiped it out and made sure not to leave any paper towel remains behind. I used a Wix 51410 hydraulic filter and Traveller hydraulic fluid from Tractor Supply. I have a Napa 1410 hydraulic filter on order at my local store to swap the current one out.

I'm in south Florida and this winter it has gone from cold (nearly 30 degrees) to hot (got up to 80 degrees today) over the course of a couple days. I keep the current Cubs in a portable garage outside, and have noticed a lot of sweating on the outside of the rear axle from the temperature swings. It's possible that there's condensation on the inside, but I can't imagine there's a whole lot. Does anyone have any other ideas to try? I have a hard time accepting that there's an internal failure since it was working so well before being parked a couple weeks.

Oak · #2 01-31-2023, 06:27 AM

I would double check the pin on the rear coupler. Did you use the correct type? They need to be the coiled spring type like these.
https://www.mcmaster.com/spring-pins.../length~1-1-2/

Oh ya, welcome to OCC.

R Bedell · #3 01-31-2023, 06:39 AM

Welcome to OCC.........

What Oak said.....Item #36

Ambush · #4 01-31-2023, 11:10 AM

Check that the shaft at the rear of the pump is still turning when you move the lever into forward or reverse. Block the tires!

Does it have a hydraulic lift? If so and that works, that means your charge pump is working.

If everything worked fine when you parked it then the system is primed and that condition won't change by sitting.

Pull the release valves out and fill the holes with hyd oil. Moving the control lever back and forth should agitate the oil in the holes which will indicate the pump case has oil. That's the swash plate moving the oil.

It could also be the roll pin securing the pump swash lever to the swash plate.

Jack the back of the tractor up, run at mid range then very slowly move the shift lever. Does it turn at all?

wilypence · #5 02-01-2023, 10:50 AM

Thanks for all the feedback so far. When I pulled the driveshaft I slid the engine forward enough and unbolted the flex disc to just pull it out that way. The input side of the hydraulic pump is untouched. I pressed the pin out of the driveshaft on the engine side to replace the fan and had replaced the pin and hub since they were both worn. I confirmed that on the back side of the hydraulic pump the shaft is definitely turning.

Unfortunately this is not a ported pump and I don't have any other hydraulic accessories, just the drive.

I removed the release valves, filled the holes with hydraulic fluid, and when I work the forward/reverse it did agitate the fluid on both sides, so I'm assuming the swash plate is still attached to the control shaft.

I jacked up the rear axle and checked that the rear tires are not moving at all in forward or reverse. They won't even move with some assistance. I did verify that when I engage forward or reverse, the shaft is still turning on the back side of the hydraulic pump. It doesn't seem to slow at all when engaging.

I did however notice while fooling around this time that in mid RPMs I notice the engine bogs down slightly when I put it in forward or reverse, and I can hear a slight whining noise although it's hard to tell because everything rattles. I did get it to lurch forward a couple inches while fooling around with it.

I have not replaced the filter yet but do have a spare I picked up from Napa. I'm just not convinced it's clogged since the rear axle was so clean when I had replaced the fluid. I also noticed after running for a while, the hydraulic pump does warm up, so I would assume it is pumping. Is it possible that the hydraulic tube is clogged??

1711Cub · #6 02-01-2023, 10:57 AM

ANYTHING is possible. Some more likely than others. Cover all of the bases AFTER the filter is changed with a proper correct replacement. Many hydraulic issues can be traced back to cheap improper aftermarket filters, or clogged old filters.

wilypence · #7 02-01-2023, 12:11 PM

Only a couple months ago I did a fluid and filter change and it has been working fine until it sat. I just swapped out the filter again and that didn't make any difference. Filter is a Napa 1410 which cross references to the MTD part number and appears to be used by several people on here. The fluid is Traveler brand and states the Hy-Tran spec on the back label.

It lurched forward a couple times, but I'm still not sure if it's the hydraulic pump or if it's a problem on the drive side.

Ambush · #8 02-01-2023, 12:26 PM

That is the correct hyd filter.

Always best to start with he easiest and cheapest, one not always being the other.

Since you can't verify the charge pump is working because of no porting, then that would be my next try. Punch or paint mark the charge pump housing and remove the charge pump to make sure the drive pin is intact. Clean and file/sand any burrs off the shaft before sliding it off to prevent damage to the seal.

It is possible that the intake tube is plugged also. You may be able to get the elbow off to check that, but the oil has to be drained. Do that while the charge pump and filter is off so you can blow through to the filter inlet.

You might still have the swash control roll pin sheared inside, but that will usually break under a load.

wilypence · #9 02-01-2023, 01:45 PM

It sounds like it's time to go ahead and pull the driveshaft again and check the charge pump and then the whole pump assembly. I have a hard time believing that anything catastrophic happened because this thing appears to be a very low hour well cared for machine from everything else I've gone through. Heck, it even has the original seat that's in fantastic shape. I cleaned off a good amount of what appeared to be road salt from the rear axle, so it's possible it was used for plowing snow in a previous life.

I'm looking at the parts diagram in the service manual. How does the charge pump rotor fix itself onto the shaft? The shaft appears to be smooth and not splined in that part of the shaft. Is there just a roll pin that goes through it like the attached charge pump photo shows? Is that what may possibly be broken?

Is it worth trying to check the pressure before tearing it down? I have an oil pressure checker that should have the right fitting for the test port.

The one last thing I may check again are the release valves to see if they are stuck, but they were freshly rebuilt from MachTech only a couple months ago. It would be strange for them both to fail at the same time.

Ambush · #10 02-01-2023, 03:16 PM

Absolutely, if you have a gauge, that's the best test. The rotor is driven with a solid metal pin.

Another member here had a similar problem. Rebuilt release valves and ended up pulling the hydro apart multiple times. Turns out TWO sets of rebuild valves were bad. Put in an old set and away it went. Be worth a try before getting too serious and removing the hydro. Be odd to have both malfunction at the same time.

Check for a broken spring under the charge relief plug.