Finally got it fixed up. There was some definite play in the idler assembly in that it could slide up and down the pivot pin. When everything is working as it should there’s only about 3/16” between the pulley and subframe hitch hook, so the idler sliding down just a little causes problems. I ended up removing the idler assembly and replacing most of the parts, so here’s some details.
It wasn’t too difficult to remove the idler assembly. First you need to remove the pulleys, belt, engage the parking brake, remove spring, then take off the clip at the bottom. It has 3 rods attached - the brake rod (front one) needs to be detached at the idler assembly. The others can be detached at the rear of the tractor and left on the assembly, then remove them after you’ve taken it out.
I ended up replacing the 4 nylon bushings, both pulleys, main idler assembly/arm, and brake rod. Nothing seemed worn enough to account for why the assembly was hanging lower and hitting the sub-frame hook. The bushings were in pretty good shape with 1 worn a bit. The pulley’s were only OK with their rotation slightly rough.
I replaced the main idler assembly because the pin the brake rod attaches to was worn about a third of the way through. The brake rod was also severely worn where it attaches to that pin. The new assembly differs in that the spacer on the pin is welded to it, and there’s no grease fitting. The lack of the fitting concerns me because if the pivot pin wears out it will be a huge pain to fix. The wear on the brake rod was severe so I added a washer underneath it.
The pin where the brake rod attaches to the brake pedal is nearly impossible to get to. There’s a plate underneath it that holds the brake and gas pedal linkages. It’s held on by 4 bolts and will drop down just far enough to get to the brake rod’s pin. I think I also had to remove a couple other pins on some linkages.
After all the above the assembly still dropped more than it should so I ended up adding a washer at the bottom of the pivot pin. Adding this washer could be a quick fix but due to all the wear on other parts I recommend you tear it down and replace as needed.