Slipping “twin belted drive pulley"

Sun Oct 26, 2008 5:50 pm

International 154 Lo-Boy
S/N 20001121-U1 32373
Age 1974

While mowing today – I noticed the PTO shaft slipping where the “twin belted drive pulley” off the main drive attaches to the PTO shaft –

I tightened the PTO adjuster shaft (nut) at the yoke assembly - this tightened the twin belts –

When I engaged the PTO the engine died -

I loosened the PTO adjuster shaft nut at the yoke assembly – the PTO shaft started slipping again –

I’m unable to adjust the “PTO adjuster shaft nut at the yoke assembly” in such a manner to allow the PTO to engage to allow the mower deck blades to turn –

What am I missing -

Thanks –

Mark T 154

Re: Slipping “twin belted drive pulley"

Tue Oct 28, 2008 9:31 am

When problems occur its good to check everything out and then we can figure out what the problem is exactly. To me it sounds like you tightened the belts too tight.


1. What kind of condition are the PTO belts in? Do they need replacement?

2. How hard are the mower deck spindles to turn? Grease the deck...

3. Do the mule drive pulleys turn free? Replace the bearings if necessary

4. Are the PTO shaft bearings free and in good condition? Does the shaft turn freely? I would loosen up the belts and see how hard the pto shaft is to turn.

On my int154 my pto belts were slipping and i removed the side cover and loosened the binder bolt on the slotted hinged plate and tightened up the belt tention nut just a little at a time until the pto stopped slipping. I didn't want to over tighten it then bearing problems can occur. Once i adjusted the PTO drive belts properly its been ok for two years now.

Re: Slipping “twin belted drive pulley"

Tue Oct 28, 2008 4:54 pm

The twin PTO belts look fine (no cracks) –

The mower deck spindles (3) and the pulleys (2) turn with ease –

I worked on this again tonight – it seems I can’t find the “sweet spot” between slipping and over tight -

We’ll continue the process -

Thanks –

Mark T

Re: Slipping “twin belted drive pulley"

Wed Oct 29, 2008 7:33 am

Sounds like something is binding up.
One of the times when you have the belt "too tight", shut down the tractor, remove the mower deck belt from the PTO, restart the engine and see if the engine dies when you engage the PTO. If it still dies then there is something binding or excessively worn in the PTO assembly.
This just eliminates the mower deck from the equation.

Re: Slipping “twin belted drive pulley"

Wed Oct 29, 2008 7:55 pm

Mine did the same thing ... cept the belts were just old and kept stretching as I adjusted them to the point of breakage ... I replaced them with kevlar re-inforced belts and they have been perfect since ... and I run some tough applications ... I.E. tiller and snowblower ....

Re: Slipping “twin belted drive pulley"

Wed Oct 29, 2008 9:13 pm

I worked on this "again" tonight -

Yep - I tried the deck issue -

Still can't find a balance on tightning the twin belts -

Took a mirror - checked the inside and the sides of he belts -

Next step is to replace the belts - this appears to be interesting - how do they come off?

Better yet - they'll come off easy with a "knife" - how do I put the replacements on - do I need to "split" the tractor?


Mark T

Re: Slipping “twin belted drive pulley"

Thu Oct 30, 2008 10:17 am

You should be able to tighten the belts until they are ready to break and the shaft should still turn (don't do that but you cannot tighten the belt enough to stall the engine unless something else is wrong). Adjust according to the owner's manual and that is the correct tennsion. There is no sweet spot.

Loosen the belts, grab the shaft and wiggle looking for looseness. If the shaft moves side to side or up and down then there is a bad bearing and the tight belt is just causing the bearing to bind. If the shaft does not move, turn the shaft, it should turn easily with the belts loose. If not then look for the source of binding either the front bearing near the double pulley or the problem is toward the PTO clutch. If the shaft turns easily then engage the PTO clutch with out anything on the PTO output shaft, i.e. loosen the mower belt. Everything should turn freely, if not then likely the problem is in the PTO clutch. Since it dies when the PTO is engaged the problem may well be one of the 4 PTO clutch bearings. You said the mower turns easily so unlikely the mower is the problem.
The PTO clutch has a pilot bearing, 2 "throwout bearings", and one shaft support bearing. A bad pilot bearing should not cause this problem, the other bearings may cause this type of problem.

If the problem is in the PTO clutch, the remove the clutch, should take only 10 minutes or so and it should be evident which bearing is bad.
I expect the PTO clutch has a bad "throwout" bearing.

Don't replace the belts yet, they may not be the problem.