PTO belt help

[our1vue 0]

I have a 2011 315-8 tractor connected to a 48" mower. I'm having problems with the mower belt slipping on the PTO pulley.  It seems like the belt is riding on the bottom of the pulley groove instead of the sides of the pulley groove. It is almost like when they machined  the grooves in the PTO pulley, they made them too wide. The only way I've been able

to get it to work is to run a 5/8" belt in the 1/2" pulley groves. But the belt sticks out of the groove about 1/8".  I think the tractor uses 1/2" belts so any factory belt I buy will have the same problem. The only other idea is to get another PTO and hope it has a narrower groove.  Has any one else ever seen this problem or have an idea of how to fix it ?

  One more thing, the down side to using a 5/8" belt is it can jump out of the groove and knock the belt that drives the wheels out of its groove (which is what happened). 

To replace the drive belt, do I just remove the side cover or does something else have to be removed ?  Is there a shop manual that shows how to do this ?

Thanks for any help you can offer.

[troutbum70 857]

I don't have an answer as to why your belt is slipping unless the sides of the belt are wore enough to allow it to run deeper in the pulley. To get the belt back on, if you remove the rear wheel and with the belt back on engine pulley you should be able to get the belt back on at the rear drive pulley. Get the belt back on tensioner and then push tensioner as far forward as it will go this will allow the belt to be placed back on drive pulley. GOOD LUCK

[daveoman1966 3,745]

Do you have the belt on the OUTER 'V' of the PTO pulley?  If so, that is WRONG.  The deck drive belt MUST be on the INNER 'V' of the PTO pulley.  

[peter lena 8,583]

can you send us some pictures? that could easily find the answer, sounds like a combo of worn pulleys and worn belt. daveoman  is on the right track , but pictures will verify your issue , pete 

[wallfish 16,985]

pics would certainly help for internet diagnostics.

I'm still trying to figure out how the attachment belt coming off can get to the drive belt and dislodge it. The drive belt should be behind the big plate of the PTO clutch.

[The Tuul Crib 7,336]

to

 

[our1vue 0]

Daveoman,

   The belt was on the inner V

Wallfish,

  I have the cost reduced version   The drive pulley is right next to the pulley that drives the mower.

I've attached 2 pictures.  One before the drive belt was put put back in its groove and one after.  You can

see how the bottom of the pulley that runs the mower is polished.  If you have any questions, please let me know.

Thanks again for all your help.

 

[gwest_ca-(File Mod) 11,033]

What is the model number and serial number of this 315-8?

 

Garry

[our1vue 0]

Garry,

    The model is 73450,  SN 240000494.  I think what I need is a 9/16 belt .

[gwest_ca-(File Mod) 11,033]

I forget why I wanted to check your model and serial. Might have been to look for any service bulletins on the subject but found none.

 

For those following along this model uses and electric clutch on the CH-Series engine.

I can see where the mower belt has been running up against the side of the transmission drive pulley. That is what you have to stop from happening.

Belts have the uncanny ability to climb a pulley to it's highest point. If you had a pulley with an inverted V for the belt to run on it would stay on top of the V. Hard to believe but they do.

I would look for misalignment of the pulleys. The front idler assembly should have the V-idler on the inside and flat idler on the outside.

A 5/8" wide belt is already out of the groove somewhat so that will make it climb out easier.

A 1/2" wide belt may have not been tight enough allowing it to climb out of the pulley. Then it climbs the transmission drive pulley until it comes off taking the transmission belt with it.

One can see how smooth the transmission drive pulley is were the belt runs. Is the pto pulley that smooth? Needs to be. I have polished the grooves with emery paper wrapped around a stick with the engine running and pto engaged. Rust on the groove surface is OK - it just needs to be smooth. Be careful.

 

Picture a drive belt around a bicycle tire. As round as they are that belt will stay in the center of that tire even if the other pulley has a fair amount of misalignment with the tire. If the tire had a flat tread surface the belt would be off in a heartbeat because it has no higher surface to run to.

Anyone that has a bandsaw is likely aware of this phenomenon and I have 6 of them.

 

Garry

 

 

[our1vue 0]

Garry,

    Thanks for the append.   Here is a little history with the tractor...

    When I got the tractor everything was fine.  But after a while the belt would slip when mowing deep grass.  I thought

it was because the belt was stretched, so I would adjust it tighter.  But no matter how tight I made it, it would still slip. I put on a kevlar belt.  That

also lasted a while and then that started slipping.  If you looked at the belts, they weren't glazed, but they still slipped no matter how

tight they were. I then noticed that the bottom of the 1/2" pulley on the PTO was shinny and realized why the belt was slipping and why tightening it up

never fixed it.  Most of the other pulleys on the tractor have V bottoms, so there no flat bottom for the belts to slip on. I looked at using a 5/8" belt

in the 1/2" pulley and since the belt was wider, there was no way it was going make contact with the bottom of the pulley. I also looked into putting

the 5/8" belt in the 5/8" pulley on the PTO, but noticed there was not that much space between the bottom of the belt and the bottom of the

pulley.  I was afraid it would only be a matter of time before the belt  would be slipping on the bottom of that pulley.

  Given all that, I figured my best option was a 5/8" belt in the 1/2" pulleys.  The belt doesn't slip in the deep grass, but I have to be careful

it doesn't jump the pulley.

  I still think the belt grooves in the PTO are slightly too wide and any belt wear causes the belts to slip on the bottom of the groove.

Probably most people aren't seeing this because they are not mowing too deep grass.  But with all the rain we get around here,

that is not an option.

Thank you all for your help

[1995 520H+96+97 937]

Is your belt cloth covered, and correct length?

Are the mule drive pulleys and spacers assembled correctly?

Is the mower deck mounted correctly in the mid attach a matic?

Pictures is what we like.

[Stormin 9,981]

  You say your mowing deep/long grass. I have the same problem over here with too much rain. What speed are you mowing at? With my C-125 if the grass is dry and shortish, I mow in 1st high. When longish and wet, 3rd low.

  Also I find that the deck drive belt loosens off after a few yards as it settles. I just readjust and it stays tensioned.

[our1vue 0]

Stormin,

   I mow in 2nd High. If the engine bogs down too much, then I change to 1st high.  By deep grass I mean 8" tall (20 cm for you metric folks )  I have checked the belt after running a bit and it is tight.

1995520H,

  Everything is attached and mounted correctly. The belt is the right length and can be tightened using the adjustment knob on the front of the tractor.

I've attached a picture of the old belt and it looks cloth covered to me.  In any case, I had a kevlar belt (the ones that are red) which I could see the cloth covering and that slipped. The picture is of my 5/8" belt, but my 1/2" had the same construction.

  I'm beginning to wonder of Toro made the grooves too wide to limit how much force they apply to the belt. I'm sure if I were to mow in a lower

gear, the 1/2" belt would not slip. But the engine has more than enough power to do the work if it can get that power to the mower blades which

it can using the 5/8" belt. 

Thanks again to everyone for the help.

 

Edited August 18, 2019 by our1vue

[Lee1977 6,647]

Comparing the 5/8" drive pullet to the others they look too wide for a 1/2" belt. I measured the bottom of a manual PTO pulley and it's 3/16" flat in the bottom. They either designed it for a 5/8" belt or someone changed the electric PTO.

[our1vue 0]

Lee1977,

  I bought the tractor new, so hopefully no one switched the PTO.  What are you measuring ?  There are 3 grooves in the PTO. Starting from the

engine side, there is a 5/8" groove for the traction belt (I think that is what you call the belt that drives the wheels).  Next is a 1/2" groove for the belt that

goes to the mower deck. Lastly there is a 5/8" groove for the belt goes to a snowblower ???   It looks like the 1/2" groove is too wide or too shallow

for a 1/2" belt.  So I'm running a 5/8" belt in that 1/2" groove. If you measure the 1/2" groove, is that the right size for a 1/2" belt ?

Another question to any 315-8 owners.  If you tried to mow really really deep grass what happens first, the belt slips or the engine stalls ?

 

[Lee1977 6,647]

I measured the very bottom flat part of the manual PTO pulley for a 1/2" belt.

Going too fast in heavy grass will stald the deck out. The reason is not the like of power it's because the grass can not get out from under the deck fast enough. I have a 18 HP Briggs Vanguard on my C-120. I can't stall the engine , But if I hear the belt squeal I have to disengage the PTO quick or it will smoke the belt. The basic design of Wheel Horse decks has been the same for the last 50 years. They changed the attachment in 1973 but the deck shell has stay the same. The decks on zero turn have a lot more room under the deck with bigger shutes to get the grass out.