Fix For Z-Force Tossing Belt

[GBHRPS]

I bought a Z-Force 48 about 3 weeks ago and have used it 4 times. Quite a learning curve from my 23 year JD 175 Hydro!

Anyway, after one event each mowing where the drive belt to the deck has hopped off the deck pulley, today it occurred twice and I decided to fix it for good. Anyone who has a similar unit with the same problem might try this simple fix.

After removing the deck from under the tractor and searching for a fix, I figured that the two idler pulleys had to be the culprits. It may have been just one of the two, but I figured to fix both would save another tear down.

The stationary idler pulled sits on a spacer about 3 inches above the top of the deck. On the side of the idler where the drive belt sits onto the pulley, I drilled a hole through the deck for a quarter inch by 4 inch long bolt to fit, so that the bolt's shaft was just an eighth of an inch outside of the pulley when fastened. Placing the belt on the pulley, I then put a flat washer and nut above and below the deck on the bolt and tightened them against each other. Now the belt cannot come off the pulley.

The other idler pulley is on a swinging bracket that allows the pulley to contact the backside of the belt, and when its spring tensioner assembly is locked in place, it takes up the slack in the belt. On my unit, the swinging bracket that this idler pulley is attached to, has an extension that has a predrilled hole in it, at the exact location where an inch and three quarter long stove bolt can be used to lock the belt onto the pulley. It looks like the factory may have had this as an option but decided against using it. Once again I loaded the belt onto the pulley, and then put a stove bolt through the bracket, fitted an inch long three eighths hollow steel tubing over the bolt, a washer and then a nut. (The steel tube won't cut the belt like the raw threads of the bolt would, I'm guessing.)

Then I reinstalled the deck under the tractor, slipped the belt over the PTO, stretched it forward and forced the belt over the deck drive pulley as I turned it. It is a muscle job to get it on, but once on and the belt tensioner properly locked, there should be no way for the belt to fly off by itself anymore.

I cut the remaining half of my lawn with no more belt issues. Only time will tell if this completely solves my problem, but I believe the issue will not return.

 

[turnerbend]

I bought a Z-Force 48 about 3 weeks ago and have used it 4 times. Quite a learning curve from my 23 year JD 175 Hydro!

Anyway, after one event each mowing where the drive belt to the deck has hopped off the deck pulley, today it occurred twice and I decided to fix it for good. Anyone who has a similar unit with the same problem might try this simple fix.

After removing the deck from under the tractor and searching for a fix, I figured that the two idler pulleys had to be the culprits. It may have been just one of the two, but I figured to fix both would save another tear down.

The stationary idler pulled sits on a spacer about 3 inches above the top of the deck. On the side of the idler where the drive belt sits onto the pulley, I drilled a hole through the deck for a quarter inch by 4 inch long bolt to fit, so that the bolt's shaft was just an eighth of an inch outside of the pulley when fastened. Placing the belt on the pulley, I then put a flat washer and nut above and below the deck on the bolt and tightened them against each other. Now the belt cannot come off the pulley.

The other idler pulley is on a swinging bracket that allows the pulley to contact the backside of the belt, and when its spring tensioner assembly is locked in place, it takes up the slack in the belt. On my unit, the swinging bracket that this idler pulley is attached to, has an extension that has a predrilled hole in it, at the exact location where an inch and three quarter long stove bolt can be used to lock the belt onto the pulley. It looks like the factory may have had this as an option but decided against using it. Once again I loaded the belt onto the pulley, and then put a stove bolt through the bracket, fitted an inch long three eighths hollow steel tubing over the bolt, a washer and then a nut. (The steel tube won't cut the belt like the raw threads of the bolt would, I'm guessing.)

Then I reinstalled the deck under the tractor, slipped the belt over the PTO, stretched it forward and forced the belt over the deck drive pulley as I turned it. It is a muscle job to get it on, but once on and the belt tensioner properly locked, there should be no way for the belt to fly off by itself anymore.

I cut the remaining half of my lawn with no more belt issues. Only time will tell if this completely solves my problem, but I believe the issue will not return.

Why didn't you just properly adjust the belt tensioner? That what it is for.

 

[OldMachinist]

There's no adjustment on the Z Force PTO belt tensioner. It's just spring loaded. I've got more than 450 hours on mine and never had a problem with mine throwing the belt unless the idler bearing was bad. I've replaced the bearing in the idler pulley a couple of times.

 

[JTKub]

GBH, this is for the Z-Force with the non-original engine? Could the output shaft be placed a little bit differently with that replacement/different engine? That would effect the tension of the PTO belt.

Joel

 

[GBHRPS]

OldMachinist,
The bearings were the first things I checked out. The mountings of both idlers was second. Everything was perfect.

JTKub,
Its possible, but I don't think so. The newer engine, although larger HP-wise, fits the chassis perfectly. The exhaust pipes to the muffler line up correctly to the openings in the chassis, etc., etc. From under the engine, the PTO pulley appears to be properly located height-wise to allow the belt to move up or down with the cutting height set on the deck.

Its hard to say just exactly what was happening when the unit spits off the belt. Nothing appears bent or worn or out of alignment. The entire tractor is in very good condition and exhibits none of the scars that telegraph that the previous owner drove by the braille method, or missed any maintenance.

I'm at a loss to be able to explain it, but I don't believe its going to be an issue any more.

Thanks for the followups, gentlemen!

 

[JTKub]

With no obvious pulley or alignment issues, it's a tough troubleshoot for sure, unless you've got an identical machine to compare with. The fab'd 44" on my Z-Force has a spring loaded assembly on the deck with a tensioner and idler on it. The belt is an extra wide and thick sucker. Not the best pic of mine, but you can just make out the idler and tensioner to the rear of the deck drive pulley:

Joel

 

[P Kurst]

Hi Gents,
I had the same issue with my ZF50. Went through four belts in 60 hours and got just about nothing from the dealer, other than a shrug and an " I don't know". Mine would jump off and just get shredded between the idler pulley and the arm that it's mounted to. I finally had enough and tracked down the dealers tech support at Cub Cadet. After explaining the situation, the tech was convinced my belt was too tight. After reading GBHRPS's story about having to muscle on the belt, I would suspect that his might be too tight as well. I couldn't get my belt on with out rolling it on either, which doesn't make any sense when you have the tensioner completely removed. Anyway, the tech told me to slack up on the big u bolt that holds the deck on in the front. I backed mine off about a half inch and I've still got my fifth belt on after 40 hours.

My new problem is the idler pulley just fell off this evening. It wound up on the ground, only to be found on the next pass. The odd thing is there doesn't appear to be any bearing left at all. It's as if it's been chewing away from hour 1 on the machine. I removed the bolt and nut that once held it in place and what's left looks like an irregular fixed sleeve of some sort, which looks nothing like Cub's part diagram for it. Guess I'm going to have to drop the deck to look closer.

 

[GBHRPS]

P K,
I'm a little confused as to what you are taking the slack off of. I assume you are lowering the front of the deck, by lengthening the two threaded rods that attach the front of the deck to the front frame? As I understand the deck's alignment, it should be about a quarter to a half inch lower in the front for proper cutting to begin with.

Even if you do lower the front, since the rear deck attach points can't be made to move forwards or backwards, the deck can't move towards the rear, so how does this put slack into your belt?

That aside, what I'm finding is even with the changes I've made to my unit (see the first post), my spring loaded idler pulley has placed the belt so far to the middle of the deck, that the belt just about touches the reverse side of the fixed idler pulley. Since the fixed idler pulley is turning the proper direction to begin with, maybe this isn't a concern?

And funny you should post about your belt problems today. Yesterday I used my unit again for the 4th time, and about a half hour from finishing I started to smell burning rubber. I stopped the mower and looked at the deck to see that something has started to shred the drive belt. After looking at things from several different directions, I decided to change the cutting height.

As it was, I had the deck set to its highest cutting height. The next level down seemed to put the belt just about level from the PTO to the front deck drive pulley. Any of the other deck height settings didn't put the deck pulleys on the same plane as the PTO pulley. Consequently the belt was running uphill from the PTO to the deck pulleys at the highest cutting height, and possibly rubbing on the frame of the tractor? Anyway, I cut the lawn with the deck at this one level down, and there was no more burning rubber smell or belt shredding.

The mystery continues. I've had this deck off so many times in the last month, I could do it with my eyes closed.

 

[hirsch56]

The belt jumping off the tension pulley is a design flaw due to bad design of the tension pulley and poor clipping discharge. Any bump or drag on the left side of the deck slackens the belt in the opposite direction of the spring pull, so the spring takes too long to take up the slack, resulting in belt jumping off the tension pulley. Bumping the right side does not do this. Since the discharge is on the right side, no one ever mows close to obstacles on that side. One always mows close to the left side of the deck because there is no discharge there, and that is the side which is sensitive to bumping. The solution would be to mount the tension pulley on the opposite side so it is sprung in the other direction. Once the belt pops to the back side of the tension pulley, there is still enough tension on it to keep running the blades, so it is not immediately obvious that the belt has hopped until you either hear the idler pulley rattle like a tinkle bell, or you smell the belt burning. One must be VERY careful not to bump anything on the left side, and if that happens, stop immediately and check the belt to be sure it is not off the tension pulley. By pulling the tension handle it pops back onto the tension pulley easily, and one can continue so long as the belt is not broken. I have mowed for many hours with a half-shredded belt this way. Some of the problem also stems from the under-deck baffle and blade design. The mulching function is so efficient that the clippings are constantly pushed up instead of out, which builds a mat above the blades and the blades are constantly pushing this mat back up. The added resistance on the blades helps to pull the tension pulley back so it is even more sensitive to a left-side bump. This year I will cut out the under-deck baffles to hopefully allow the clippings to fall outside the blade diameter and avoid a mat buildup, since the airlfow does not seem to push clippings out the discharge well. I will also coat under the deck with graphite slick-coat grain chute spray.

 

[GBHRPS]

You can see from the date of this post and my first posting on this topic, that 2 1/2 years have passed since I "fixed" my problem with the drive belt being tossed.

I'm pleased to report that I've had absolutely no issues with the problem occurring since the fix back in June of 2010. The new belt I installed at that time is still on the machine and still looks brand spanking new. And, yes, I no longer use the top most height adjustment when cutting the lawn. There is just too much height differential between the drive and deck pulleys at that position, that I believe would cause premature wearing of the belt.

My initial fix has solved the problem, and I'm extremely pleased with how well this tractor has performed since.