I used to struggle to get the PTO belt on by myself. I have a 108 that I've been using for 41 years. Same deck and frame and tractor (other than model number as you).

Decades ago, I'd thread the belt on the pulleys and sit in front of the tractor and push the deck back with my feet hoping one of the hanger latches would pop into a hole in the support frame. It was always a struggle.

About 20 years ago I discovered that I could put the belt over the pto, thread it through the mule drive and without removing the deck, work it over the deck central pulley by rotating the pulley by hand, working the belt into the pulley groove. That's how I do it on all my Cub mowers now---a couple 1450s, a 108 and a 128.

I learned just a couple years ago that the support frames are different for the triangular decks (38 and 42) than for the stamped decks (44, 50) and are not interchangeable. They fit, but the specified belts don't. I knew the mule drives were different (tilted pulleys for the 44/50 decks) but didn't realize the support frames were different as well.

It looks like you have the proper frame for that deck. The specified belt should fit unless the support frame has been modified somehow? Or the mule drive is not fully seated in the QA notches? Or the tension spring is too stiff? Or the tensioning bolt has been cut short--so you can't slacken the belt enough--running out of thread? Or the center pulley has been changed to a different size?

Some folks have tried to put a 1/2 x80 inch belt on when the specified belt is 3/8 x 80. The narrower belt sits down in the pulley grooves further so it can be shorter than a 1/2 inch belt would need to be. BTW, 1/2 inch belts pretty much suck in this application, they roll out of the pulleys, don't contact the pulley sides correctly, and generally fail as a result.

Frank...I'd love to see a video of that method! That is one I've not tried. I usually start at the PTO, then put it on the spindle, making sure there are no twists (I've done that more than once) then just adjust those front pulleys till I get the belt on both.

Regarding the tensioning bolt - I sort of think part of it may have broken off at one point now that you mention it, and so, as you say, is now shorter. There must have been some other issue with it as well cause I have two nuts on it. I seem to recall that it used to slip otherwise (worn threads?) So one nut tightens up on the other. So much has happened on this tractor over the past 40 years, and I didn't write down everything I ever did to it. I must make a correction to an earlier post in that I just noticed the right pulley (in the front) is white and thus a replacement, so whether or not it is exactly the same size as the left one is uncertain without taking off the mule drive. Where the spring hooks into the hole at the front of the drive actually wore all the way through just the other year, and so had to take it to a welding shop to be repaired. I have no doubt that not all is exactly, shall we say, copacetic. The underside of the deck is a trainwreck in that there are no longer any baffles. They've all worn away. Remaining are a few jagged pieces that do absolutely nothing. There's also a pretty impressive hole on the back of the deck as well. At one point I drilled some small holes on either side of it and attached - with small nuts and bolts - a small strip that I cut from a section of spouting, but it never held up. I don't do any welding...never have...so the spouting seemed like a workable solution. Now, I no longer worry about it. Doesn't take long till the hole simply gets clogged with clumps of grass - and then it can happily stay that way till fall! Hole hasn't gotten any bigger, so, it's all good. There is some play in the spindles but really not bad. Thankfully this 129 is no longer in use for my lawn mowing. Bought a new John Deere X590 the other year (I know...such a terrible thing to even mention on a vintage cub forum) so use that to mow the lawn. The cub no longer plows snow either. It has earned a well-deserved retirement from all jobs other than mowing a few walking paths in the woods across from my house on PA Fish and Boat property (long complicated story). I must say, though, that I love the power steering and shorter turning radius on the JD. Actually wish I would have bought it or something like it years ago. Gets the job done so much faster - plus it's a larger deck. The cub steers like a Mack truck in comparison.

I have done it the same as Frank has been doing it, just be sure you watch your fingers.

Oh, Lordy...have I ever gotten my fingers pinched, and cut, and whatever else...over the years. Worst thing ever was when I had the tractor separated 2 years ago to do both a cork gasket job and put in a new engine (talk about a long, complicated story). I had the hydro on a jack (for probably about 3 months in all) and at one point when moving it around it nearly slipped off the jack. Had a whole managerie of boards wedged under the thing all sorts of ways to try and shore it up. That was the only time I ever separated the tractor and hopefully the last. What was REALLY crazy was that, with the old engine AND trans out of the frame at the same time, there was essentially no weight left, so I actually had the thing wedged against my workbench (again, with an assortment of boards, hollywood blocks, whatever - to prevent it from moving around. Put the trans back in first, then the engine. Probably the most complex mechanical undertaking I've ever embarked on. Even crazier...while the hydro was on the jack all that time, for a few weeks we were away on a cruise ship that nearly ran aground off the coast of Norway (google Viking Sky March 23, 2019). My wife and I, along with 400+ passengers, had to be evacuated off the top deck of the ship by helicopter during a bomb cyclone. So after that incident, coming back home to get back to work on the cub seemed like a treat! Luckily, the trans was still on the jack.

Making no sense!

If you guys are having that much trouble putting on a mule drive belt, SOMETHING is truly amiss!

Never have had that issue,
Back off the adjusters, install the belt and readjust.

Sorry!! You're right! Meant to say that the offer was put in for an 81" belt.

As sawdustdad suggested, I'm pretty sure that the issue is the tensioning bolt not being as long as it once was. Could be that's when I switched over to the slightly larger belt. Can't remember at this point.

I have trouble sometimes with putting on belt and it's because the pulleys on mule drive are hung up where they're hanging.:beerchug:

Yeah, well, lifting and moving that deck around sure doesn't get any easier, especially after injuring my back last summer plus some shoulder impingement issues. On my new Deere, which has a significantly larger deck, I won't even attempt to hassle with it - dealer picks up the tractor, takes it along, and does all the deck (plus whatever other work I request). Except this year they seem to be really behind schedule. Delivery and service charge is worth saving the strain on the back!