John Deere LT155 Hydrostatic Transmission Freewheeling Issue

[JBASport]

I have posted before, but struggling to understand what is wrong with my John Deere LT155. The mower was becoming sluggish, so thought I would try changing the oil. I removed the transmission, drained the old oil and replaced with new. I took the opportunity to replace the drive belt too. I made sure I located the axle keys on the shaft to secure the wheels, as I know that can be a problem if they drop out. I started the mower and there was no drive, either with the freewheeling lever in or out. I am at a loss as to know what to do next. I have gone over all the things I did and cannot find anything obvious I might have done to cause this issue. However I am now wondering if there is something I have or have nor done in refitting the transmission into the mower.
With the back wheels free to turn, they rotate freely, regardless of whether the freewheeling lever is in or out. Should that be the case? I am just trying to work through the options to troubleshoot the problem, thanks, Terry

 

[bertsmobile1]

Have you purged the air from the transmission ?

 

[JBASport]

I soun the fan blade around

Have you purged the air from the transmission ?

When it was out of the mower, is that what you mean, or does it need something more mechanical? Thanks for your help.

 

[bertsmobile1]

Air gets trapped in the cylinders of the pump & motor.
So you jack the mower up with the rear wheels off the ground.
Start the engine and let it run for a few minutes then throttle down as low as the engine will run
With the bypass valve open ( push mode ) move the pedals slowly from full forward to full reverse till the wheels respond full speed which may be anything up to 20+ cycles .
Then engage the bypass valve ( drive mode ) and repeat above

You may need to repeat these steps a few times
Drop the mower onto the ground & go for a test run.

 

[JBASport]

T

Air gets trapped in the cylinders of the pump & motor.
So you jack the mower up with the rear wheels off the ground.
Start the engine and let it run for a few minutes then throttle down as low as the engine will run
With the bypass valve open ( push mode ) move the pedals slowly from full forward to full reverse till the wheels respond full speed which may be anything up to 20+ cycles .
Then engage the bypass valve ( drive mode ) and repeat above

You may need to repeat these steps a few times
Drop the mower onto the ground & go for a test run.

Thanks for that, will give that a go. Appreciate your help. Terry

 

[JBASport]

T

Thanks for that, will give that a go. Appreciate your help. Terry

Hi, I have tried to do as you say, but it looks as though I have a further issue I need to sort first, With the mower jacked up, it looks as though I have a tensioing problem with the main drive belt. It is spinning on the main engine pulley, so not rotating through any of the pulleys and transmission unit. I have checked the routing and looks exactly as it came off. As it is a new belt, I need to see whether it is the correct one for the mower (do you check the length by measuring the inside or outside of the belt) Also one of the pulleys had a elogated slot for adjustment. I wondered as I had to take it off to route the belt, I may have located it at the wrong end of the slot (I slid it towards the other pulley, to the rear). Once I get the drive sorted I can look at purging it. Thanks again for your help. Terry

 

[JBASport]

Hi, just an update. I have managed to adjust the belt tension and it is driving the transmission blade ok now. However, I have tried to purge the transmission as you suggested and cannot get the wheels to move, with either the freewheeling lever in or out. I have taken a video but it seems to be too large to upload. Will try and reduce its size and if successful will upload it. Thanks again, Terry

Hi, I have tried to do as you say, but it looks as though I have a further issue I need to sort first, With the mower jacked up, it looks as though I have a tensioing problem with the main drive belt. It is spinning on the main engine pulley, so not rotating through any of the pulleys and transmission unit. I have checked the routing and looks exactly as it came off. As it is a new belt, I need to see whether it is the correct one for the mower (do you check the length by measuring the inside or outside of the belt) Also one of the pulleys had a elogated slot for adjustment. I wondered as I had to take it off to route the belt, I may have located it at the wrong end of the slot (I slid it towards the other pulley, to the rear). Once I get the drive sorted I can look at purging it. Thanks again for your help. Terry

 

[Rivets]

This is my procedure on purging hydros, same as Bert’s, just a little more in-depth.

This is how I do it and I warn you this may take some time. Minimum of two hours unless you get real lucky.

1. Block both front wheels so the unit can’t roll forward.
2. Jack up the rear end and put on jack stands so the wheels are at least 2” off the floor.
3. Start up the unit, run just above idle and push the sticks forward about halfway and hold for 30 seconds.
4. Bring sticks back to neutral and let it run there for 30 seconds.
5. Pull back on the sticks about halfway and hold for 30 seconds.
6. Bring sticks back to neutral and let it run there for 30 seconds.
7. Repeat steps 3-6 a half dozen times.
8. Shut off unit and let it sit for 15-20 minutes.

During these steps the wheels should be turning slowly, but may turn faster as you go through each cycle. I have had units which the wheels don’t start turning until the fifth or sixth cycle.

9. Repeat steps 3-8, but this time move sticks to full travel and hold for 1 minute.

If you are lucky your wheels should be turning much faster. If they do not turn faster repeat step 9. Now is when you need patience. Why? Depending on how much air is in the system, you may have to going through the steps 5-10 times before you get all the air out. It will be helpful if you have an assistant who can put his foot on the wheels to see if he can stop the wheels from turning. I’ve had a couple of units I’ve had to let the unit sit over night and repeat the steps the next day, because I couldn’t get it to push out all the air.

10. Now that your wheels are turning fast and you can’t stop them, cycle 6 times through left and right turns at all speeds.

If everything looks good, drop the unit off the stands and test the unit.

REMINDER: KEEP YOUR EYES ON THE FLUID RESERVOIR OR FLUID HEIGHT, AS YOU MAY HAVE TO ADD EACH TIME YOU SHUT THE UNIT OFF. LOW FLUID WILL RESULT IN POOR OPERATION. AS YOU REMOVE AIR WHO NEED TO REPLACE WITH FLUID.

There are other ways to do this, depending on your equipment, but this is how I do it. Also, not uncommon for one pump having more air than the other, so you must keep checking both each time.

Forgot to ask; did you use the fluid recommended by the manufacturer? If not, this could add to the problem.

Good Luck, have PATIENCE.

 

[JBASport]

Hi, just an update. I have managed to adjust the belt tension and it is driving the transmission blade ok now. However, I have tried to purge the transmission as you suggested and cannot get the wheels to move, with either the freewheeling lever in or out. I have taken a video but it seems to be too large to upload. will try and reduce its size and if sucessful will upload it. Thanks again, Terry

Hi, I have tried to do as you say, but it looks as though I have a further issue I need to sort first, With the mower jacked up, it looks as though I have a tensioing problem with the main drive belt. It is spinning on the main engine pulley, so not rotating through any of the pulleys and transmission unit. I have checked the routing and looks exactly as it came off. As it is a new belt, I need to see whether it is the correct one for the mower (do you check the length by measuring the inside or outside of the belt) Also one of the pulleys had a elogated slot for adjustment. I wondered as I had to take it off to route the belt, I may have located it at the wrong end of the slot (I slid it towards the other pulley, to the rear). Once I get the drive sorted I can look at purging it. Thanks again for your help. Terry

This is my procedure on purging hydros, same as Bert’s, just a little more in-depth.

This is how I do it and I warn you this may take some time. Minimum of two hours unless you get real lucky.

1. Block both front wheels so the unit can’t roll forward.
2. Jack up the rear end and put on jack stands so the wheels are at least 2” off the floor.
3. Start up the unit, run just above idle and push the sticks forward about halfway and hold for 30 seconds.
4. Bring sticks back to neutral and let it run there for 30 seconds.
5. Pull back on the sticks about halfway and hold for 30 seconds.
6. Bring sticks back to neutral and let it run there for 30 seconds.
7. Repeat steps 3-6 a half dozen times.
8. Shut off unit and let it sit for 15-20 minutes.

During these steps the wheels should be turning slowly, but may turn faster as you go through each cycle. I have had units which the wheels don’t start turning until the fifth or sixth cycle.

9. Repeat steps 3-8, but this time move sticks to full travel and hold for 1 minute.

If you are lucky your wheels should be turning much faster. If they do not turn faster repeat step 9. Now is when you need patience. Why? Depending on how much air is in the system, you may have to going through the steps 5-10 times before you get all the air out. It will be helpful if you have an assistant who can put his foot on the wheels to see if he can stop the wheels from turning. I’ve had a couple of units I’ve had to let the unit sit over night and repeat the steps the next day, because I couldn’t get it to push out all the air.

10. Now that your wheels are turning fast and you can’t stop them, cycle 6 times through left and right turns at all speeds.

If everything looks good, drop the unit off the stands and test the unit.

REMINDER: KEEP YOUR EYES ON THE FLUID RESERVOIR OR FLUID HEIGHT, AS YOU MAY HAVE TO ADD EACH TIME YOU SHUT THE UNIT OFF. LOW FLUID WILL RESULT IN POOR OPERATION. AS YOU REMOVE AIR WHO NEED TO REPLACE WITH FLUID.

There are other ways to do this, depending on your equipment, but this is how I do it. Also, not uncommon for one pump having more air than the other, so you must keep checking both each time.

Forgot to ask; did you use the fluid recommended by the manufacturer? If not, this could add to the problem.

Good Luck, have PATIENCE.

Thanks for that. When you mention put the sticks forward, do you mean the forward and reverse pedals?
It is really difficult to access the top up fluid on these Tuff Torq units as I gather they are supposed to be none serviceable! I am sure I will find a way to do it though.
Yes, I have used the fluid (TRIAX Trans Zero 20W-50 Full Synthetic HydroStatic Transmission Oil)

Many thanks, Terry