drive belt keeps coming off transaxle pulley

[4girlsdad]

Howdy - I have a 1997 craftsman tractor with a 24hp kohler engine and hydro transmission - model #917.258910. The engine started shuddering when I put it drive (but reverse is ok), then it shredded the ground drive belt - which was very old.

I put on a new belt, after a half hour the tractor stopped, the engine stalled and the belt ended up in between the transaxle pulley and the transmission.

After this I noticed that the belt keeper above the transaxle pulley was missing, so I made a new one and installed it. Same think happen, only this time enough of the home-made belt-keeper was left that I could tell then the pulley had sheared it off - I can see 2 pulley tracks in the keeper. Belt also jumped off after a few minutes.

I'm sure that I'm threading the belt correctly, but I noticed that the pulley with the fan is not in the same vertical plane as the transaxle pulley, so I'm thinking that they're not aligned. The fan pulley does point directly to the transaxle pulley, but it comes to it at an angle.

I can't find anything about the correct alignment of the pulleys, and I'm afraid if I try to bend the fan pulley assembly so it's in line with the transaxle pulley I'll put it out of alignment with the engine idler pulley.

If anyone has a picture or diagram of the correct alignment I'd be much obliged.

I live in New Hampshire, use the tractor as my snowblower, and will be up to my eyeballs in snow soon if i don't get it fixed.

Thanks -

 

[Rivets]

From your description I'm suspecting multiple problems. Missing belt guides, poor belt alignment, bad pulleys, bad idler pulleys and frozen or sticking idler arm will all contribute to loosing belts. You are going to have to check each of these. Also on this system you are going to have to use any OEM belt, as the wrong length or pitch will cause the belt to jump, due to the change in belt angle. You will have to check everything and replace anything questionable. Page 24 of this manual might help.

http://www.managemylife.com/mmh/pd_download/lis_pdf/OWNM/L0805481.pdf

 

[reynoldston]

That is always my first question, are you using a OEM belt, when a job comes into my shop with that problem.

 

[4girlsdad]

I've been using craftsman belts -
the pulleys seem ok, no flat spots and they spin freely

the only thing that looks off to me is the angle of the pulley with the fan on it, but I don't know what it should look like

 

[reynoldston]

Hard to diagnose something like that over a forum. bad bearings, something loose, bent brackets, wrong belt, is the transaxle or engine loose on it mounts, you say the pulleys spin freely but a bad bearing will spin freely do they wobble ???

 

[bertsmobile1]

As I cant see it from here, so this is the slightly longer than necessary easy to understand & see method
Start by pulling the rear body work off and remove both rear wheels so you have a good clear view of the rear axel & transmission.
When viewed from directly above the pulley should be in the middle of the axels
So from either side the pulley spindle should be dead vertical from the transmission.
Grab the pulley & try pulling it up & down there should be no more than 1/4" of movement and the less the better.
Try moving it left - right & front - back. No movement at all in these directions is acceptable.

Rotate the pulley and check it runs true, if there is any wobble it is US.
If you find wobble look closely to see if it is in the pulley or shaft.
Down side is a lot of theses trannies are not repairable, principally because you can not get parts. Good side is replaccements are relatively cheap.
However the pulley itself & fan is replaceable and are a lot thinner than the old ones so they do bend or break rather than breaking the box itself.

Needless to say there should be zero movement between the tranny and the mower body, it must be rigidly bolted to the frame ( yes the bolts do drop out during use ).

From what you have said I would summise the belt keeper fell off & got jambed between the belt and pulley causing the shuddering.
This has either bent the pulley or input shaft which now has the pulley out of alignment

 

[SeniorCitizen]

Those with idler pulleys are usually the ones that take the beating and become out of alignment.

 

[mechanic mark]

CRAFTSMAN TRACTOR Parts | Model 917258910 | Sears PartsDirect Use OEM parts from sears. Rivets is correct, remove deck & check parts he mentioned for replacement.

 

[OldDuffus]

Howdy - I have a 1997 craftsman tractor with a 24hp kohler engine and hydro transmission - model #917.258910. The engine started shuddering when I put it drive (but reverse is ok), then it shredded the ground drive belt - which was very old.

I put on a new belt, after a half hour the tractor stopped, the engine stalled and the belt ended up in between the transaxle pulley and the transmission.

After this I noticed that the belt keeper above the transaxle pulley was missing, so I made a new one and installed it. Same think happen, only this time enough of the home-made belt-keeper was left that I could tell then the pulley had sheared it off - I can see 2 pulley tracks in the keeper. Belt also jumped off after a few minutes.

I'm sure that I'm threading the belt correctly, but I noticed that the pulley with the fan is not in the same vertical plane as the transaxle pulley, so I'm thinking that they're not aligned. The fan pulley does point directly to the transaxle pulley, but it comes to it at an angle.

I can't find anything about the correct alignment of the pulleys, and I'm afraid if I try to bend the fan pulley assembly so it's in line with the transaxle pulley I'll put it out of alignment with the engine idler pulley.

If anyone has a picture or diagram of the correct alignment I'd be much obliged.

I live in New Hampshire, use the tractor as my snowblower, and will be up to my eyeballs in snow soon if i don't get it fixed.

Thanks -

Bolts worked loose from the hydrostatic transmission (at least on one side) is what happened to your mower (as it did mine). In short, the bolts worked loose from the hydrostatic transmission on one side (right side in my case) allowing the aluminum body (the whole transmission on one side) to sag as evidenced by the outboard drive wheel leaning its top toward the mower like it is about to fall off. I saw exactly what you describe: the fan pulley was misaligned and was in a plane much lower than the idler pulley; they no longer lined up or no longer in the same plane. I hope this helps. I reduced the size of my photo so it would upload. Notice the significant gaps, between 3/4 inch and 1 inch at the bottom where the bolt boss on lower right should be drawn to the black weldment on the left and was tight before three bolts dropped out. The three missing bolts dropped out from the two lower bosses at bottom left of transmission one of them is hid further into plane of photo. Also, a thinner bolt dropped out of the vertical cylinder boss in upper middle of picture leaving a gap of about 1/2 to 3/4 inch between top of boss and the black angle bracket at picture top.

One more thing...When it comes time to replace a shredded or ruined hydrostatic belt (ground drive belt), ironically you will want to remove these same bolts to purposely force a sag in the transmission so as to rotate the pulleys with a fan on them inboard away from the mower framework or the belt cannot slip past to get it raised off of the transaxle pulleys.

 

[bertsmobile1]

Always worth revisiting but this is a 2015 thread & has been resolved .