Would like info. Please

[maine home 0]

Hi, I'm burning up PTO belts on a GT1600 mower. Could the pulleys by the tighter be worn out? The outside belt keeps jumping to the inside pulley?

Would also like to know what the adjustment on back of deck is for? 

Thank you 

Edited June 29 by maine home
Added pics

[peter lena 9,984]

@maine home  seams like  spindle bearing , lubrication failure  ,  incremental , bearing , stop / start  'probably causing  belt jump . not familiar  with your unit , would bet on combined rotational  drag  , what model mower do you have , brand ?   pete

[JCM 11,323]

  to   

[ebinmaine 79,893]

 

We don't use the mowing deck here but others will be along soon. 

 

@MainelyWheelhorse

@Blue Chips

@midpack

 

Another Mainer here.  

[Bill D 3,024]

Welcome.   Any pictures?  They are very helpful when diagnosing issues like this.

[midpack 1,147]

IIRC the adjuster on the back of the deck is to level it.

The belt jumping, is that in the mule drive?

Check that the pulleys were put on in the right order. I had one that was mixed up before I got it. I also had a rear discharge that I put on so that the blades were turning backwards. I finally put an arrow with magic marker on the deck to clarify which way to put the belt on

[MainelyWheelhorse 2,969]

1 hour ago, maine home said:

Hi, I'm burning up PTO belts on a GT1600 mower. Could the pulleys by the tighter be worn out? The outside belt keeps jumping to the inside pulley?

Would also like to know what the adjustment on back of deck is for? 

Thank you 

@maine home Hi fellow Mainer! What size is the mowing deck? Pictures of your setup should definitely help us figure out what’s wrong. There could be many things that could cause the belt to jump. The smaller 37’ inch deck use one belt from the PTO to the deck. The bigger ones like the 42” inch ones use two. One from the PTO to the front most middle pulley on the deck, and one just on the deck to run the mowing blades. The belt from the PTO to the deck is on the mule drive. If it’s jumping, something could be wrong with the pulleys. If it’s the mule drive it might not be tight enough, or something is off there. There’s a few possibilities.

Edited June 29 by MainelyWheelhorse

[Blue Chips 821]

Welcome, fellow Mainer. 

All of the above comments are worth considering. Post a picture or two if you can. Make sure the photos show how you're routing the belts.

This thread is reminding me that our front lawn is getting deep enough to hide a large groundhog and needs some attention from my mowing deck. 

[Ed Kennell 46,716]

to the   

[8ntruck 9,126]

to the forum.  

 

Make sure that your pulley bearings and center mower shaft bearings are not sloppy and spin freely.  Working from memory here, I think that the pulley spacers on the mule drive shaft are different lengths.  If you get them in the wrong place, belt alignment will be a bit off.  Sorry, but I don't remember right now which one goes where.

 

Belt tension should be in the neighborhood of having about 1/2" belt flex on each side of the belt halfway between the PTO and mule drive.

 

A remote possibility is that the mule drive shaft might be bent.  This would certainly mess with pulley alignment.

 

Good luck.  Please, when you find the solution, post it - share the knowledge.

[maine home 0]

I just edited my post. Added pics. The sparer is spit see pic. I need part number. 

[Handy Don 17,089]

At first glance, it looks like the engine-to-deck belt might be the right length but looks to me to be not the right width (or else it is extremely worn). 
A properly fitted belt should, when new, ride with the outer surface of the belt being very slightly above the edges of the V pulley. 

[maine home 0]

On 6/28/2026 at 8:38 PM, MainelyWheelhorse said:

@maine home Hi fellow Mainer! What size is the mowing deck? Pictures of your setup should definitely help us figure out what’s wrong. There could be many things that could cause the belt to jump. The smaller 37’ inch deck use one belt from the PTO to the deck. The bigger ones like the 42” inch ones use two. One from the PTO to the front most middle pulley on the deck, and one just on the deck to run the mowing blades. The belt from the PTO to the deck is on the mule drive. If it’s jumping, something could be wrong with the pulleys. If it’s the mule drive it might not be tight enough, or something is off there. There’s a few possibilities.

It's a new belt but it twisted when it jumped the pulley. Now it has a bad twist in it and will not work.

 

[maine home 0]

16 hours ago, 8ntruck said:

to the forum.  

 

Make sure that your pulley bearings and center mower shaft bearings are not sloppy and spin freely.  Working from memory here, I think that the pulley spacers on the mule drive shaft are different lengths.  If you get them in the wrong place, belt alignment will be a bit off.  Sorry, but I don't remember right now which one goes where.

 

Belt tension should be in the neighborhood of having about 1/2" belt flex on each side of the belt halfway between the PTO and mule drive.

 

A remote possibility is that the mule drive shaft might be bent.  This would certainly mess with pulley alignment.

 

Good luck.  Please, when you find the solution, post it - share the knowledge.

Check my pictures. The third spacer broke the weld spitted (see pic). That looks like the problem is?

[maine home 0]

On 6/28/2026 at 8:38 PM, MainelyWheelhorse said:

@maine home Hi fellow Mainer! What size is the mowing deck? Pictures of your setup should definitely help us figure out what’s wrong. There could be many things that could cause the belt to jump. The smaller 37’ inch deck use one belt from the PTO to the deck. The bigger ones like the 42” inch ones use two. One from the PTO to the front most middle pulley on the deck, and one just on the deck to run the mowing blades. The belt from the PTO to the deck is on the mule drive. If it’s jumping, something could be wrong with the pulleys. If it’s the mule drive it might not be tight enough, or something is off there. There’s a few possibilities.

36?

[peter lena 9,984]

@maine home those belts  are showing you the way  , looks like  total  collective drag failure , have any help on this ?  like someone  that  owns  a similar set up ? would also bet the mule drive bearings , and  pto  spindle needle bearing  is dry , hanging up , thats  typically the  engine heat  , destroying  lubrication ,  minimising  belt driven  spin up , actually not a  bad job , done a few , my experience , is to  change out  all related lubrication in every bearing , lucas x tra hd , green chassis grease ?  550 deg  flash point  , polyurea rated , to stay with bearings , done this on 3 decks  , never failed again , or make noise . you do not know what the bearing  lube is , original fill is based on cheap , dollar saving  stage  of  assembly, they will work , but  will soon be whyining  with  noise.  why not eliminate that stage ?  only  my experience on related failures , experienced helper  , will  really , save it , pete   

[peter lena 9,984]

@maine home  never look at a  rotational  anything , as a single area , fix / repair , to me thats a  glairing  mind set . that  deck pulley with  imploded bearing  , would have gotten after that  , from the start  , can imagine the related , pto lever set up , did this years ago , basic  functional improvement , at every stage  , makes this set up work , as it should ,  pete