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Kevin, Technician
Category: Small Engine
Satisfied Customers: 714
Experience:  Over 10 years as a Deere Service Tech.
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How do I adjust the drive belt tension on a John Deere LT155

Resolved Question:

How do I adjust the drive belt tension on a John Deere LT155? Mine slips and won't make it up any kind of incline. I need it to push snow this winter and there's no way the way that it is running right now.
Submitted: 5 years ago.
Category: Small Engine
Expert:  Kevin replied 5 years ago.

Hello, my name is XXXXX XXXXX I can help you with your question.


The belt on your mower is spring tensioned although it does have a slotted adjustment up at the drive pulley end. I suspect that there is most likely another issue causing the problem you describe.


I have a couple of questions about your mower that will help me narrow down the source of your problem.


  1. When you first start your mower does it seem to drive with good power for the first few minutes and then start to become sluggish or weak?
  2. When you notice the low power problem do you hear the belt squealing or smell it burning a little?

Let me know when you get a chance and I will do my best to help you resolve the issue.




Customer: replied 5 years ago.

1. A little bit. Seems to be a little worse as it warms up but still at first it can't make it up the hills.

2. I've noticed a slight squeeling sound a few times and have smelled the rubber burning smell.

Also, when it won't go up the hill (even small ones) if you rock a little bit it seems to grab and go a little better.

Expert:  Kevin replied 5 years ago.

Thank You for helping me out with the details. Theres nothing worse then steering some one in the wrong direction due to lack of information.


Based on your description I would highly recommend replacing the belt. Once the belt has slipped it gets a hard glaze on it that prevents it from ever being able to hold as it should.


Replacing the traction drive belt is a relatively simple task. Use the following steps to install the new belt.

  1. Engage the parking brake, this will move the tensioner assembly back making it easier to install the new belt.
  2. Loosen the nut retaining idler pulley #32 in the diagram, this will allow you room to put the belt on the pulley.
  3. You will need to slide the belt adjusting pulley #24 towards the engine pulley but note its previous location so it can be placed back in the same spot later.
  4. You may need to remove the steering rod from the bell crank in order to route the new belt in place.
  5. Route the new belt as depicted in the diagram and tighten the #32 idler while making sure the belt guide does not hit the belt.
  6. slide the #25 idler back to its previous location and tighten down.
  7. Install the previously removed steering link from the bell crank.
  8. Start the engine and disengage the parking brake, make sure the new belt isn't rubbing on anything.

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If all checks out good, you should be all set.


If my answer has completely answered your question please hit the green "Accept" button so that I can get paid for helping you. If you need further assistance please respond to this message and I would be happy to help you out.






Customer: replied 5 years ago.
I've replaced the belt before and it seems to help for a while but does not seem to fully fix the problem. I've taken it in to the local John Deere dealer and they've done something that tightened the belt and did not replace it to my knowledge.
Customer: replied 5 years ago.
Any other suggestions? If that's the only advice you have it to change the belt, I'd like to try that first to see if it works before I accept your answer. Would that be alright?
Expert:  Kevin replied 5 years ago.

There are a couple of things to look at that could prevent the belt from staying tight or let the belt slip. The belt tensioner bracket pivots on a pair of plastic bushings #6. It is possible that the bracket has become stiff at the pivot point preventing it from maintaining tension. When you depress the parking brake pedal it moves this tensioner an de-tension's the belt. Make sure that the brake pedal moves freely, it would also be a good idea to spray some lube on the pivot point of the bracket. Secondly the #24 idler should be moved furthest away from the drive pulley to ensure full tension.


Since you have smelled and heard the belt slipping I assumed that the hydro unit was not the issue. It may be worth wile to check the oil level in the hydro. Unfortunately they claim your hydro to be service free and made checking the oil very difficult. The hydro will squeal when it bypass internally so it is possible you could have a hydro problem.


In order to check the oil level you need to remove the vent plug (#7 in the attached diagram). The oil should be only about an inch down from the top of the vent plug hole. You will find that the vent plug itself is very difficult to access and even more difficult to add oil if needed. The recommended oil is Low Viscosity HyGard oil. If you slightly over fill the oil level it might leak out the vent plug after the transaxle gets hot but won't hurt anything.


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If you find that the oil level is ok then it is most likely that the transaxle is worn internally. Rather then discard the transaxle for a pricey new unit you can often get a little more life out of it by draining the oil and filling with 10w30 engine oil. The 10w30 engine oil is thicker and won't leak past the worn internal components as fast. The catch is that the transaxle is not equipped with a drain plug so the transaxle must be removed from the tractor and the oil drained from the vent plug #7 hole. This is not a permanent fix but it might get you by for another mowing season.


Hope this helps,


Kevin, Technician
Category: Small Engine
Satisfied Customers: 714
Experience: Over 10 years as a Deere Service Tech.
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