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Mower Deck belt woes

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Well-known member
Jul 8, 2006
Western Maine
James MacDonald
I imagine I'm going to take some flak over this question. So, I'm ready.
Some time ago I purchased a Cub Cadet 125 with mower attached. It ran ok. and later I installed a snow blower.

When I tried to reinstall the mower deck for the spring the belt for some reason was "way" too tight.
I bought a new IH-489397-R3 (3/8" x 75 1/2") belt per the FAQ, and it's the same way too tight.

The PO has done some funky things so I'm thinking somehow, I might have a mis-matched deck and sub frame. Picture attached.
It's a 482U1113 deck (not sure how to tell serial numbers on these decks) mower both the mower and mule drive are quick attach. Mower has a 5" pulley, and the mule drive idlers are 3"

I did try and try etc. to figure what exactly I need for a belt even tried a rope simulation and measured that. Dammit if it doesn't measure out to 75 1/2" :feint:. I see that Charlie has two 3/8 belts that are 79" and 80" long so I'm thinking maybe one of those.
The PO it seems had the belt on so tight that it has done damage to the spindle as it is flopping around. I'll tear into that once I solve the belt issue.

I have attached a photo I took today to show just what I have with the tension spring disconnected and the adjustable rod as loose as I can get it. Is there any way to tell from the photo what belt I need? I need help bad: thinking maybe drinking in the afternoon might help!
I do have a second 48" deck that i have for a 123 that's waiting to be worked on and that deck looks exactly like the one that arrived on the 125.


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James...opinion..fix the spindle first or you might eat a new belt in a few seconds ..From what I'm seeing your present belt appears to be about 2 in. short if adjustment is backed off all the way...If you measured with a 1/2 rope you should be very close. go to local auto parts and try a 77 in. belt..Keep it clean and if needed you should be able to trade back in if it doesn't fit right.....The thing with p.o. is you don't know what might be changed if you don't have a comparison...
I have had some success with the blue/green Kevlar belts from tractor supply, but only after I worked hard to get the 2 pulleys directly below the pto pulley (1250) aligned well to the pto. They come in 1” size increments I think. But I don’t mow very often…. When I do it’s 1 acre of grass with the deck down and 3/4 acre of field with the occasional rock, and the deck all the way up. I believe I ended up with a 79” belt.
I have the best luck putting the belt on the PTO pulley and mower pulley first, mule drive idler pulley next and spring loaded pulley last.
That appears to be the correct subframe/mule drive for that mower deck. I have always installed the belt onto the PTO and mule drive pulleys and then rotated it onto the mower deck center pulley. The spring on the mule drive pulley will give the required slack to roll the belt onto the mower deck pulley.
In the picture I have the spring on the mule drive disconnected. It's still too tight and there is nothing left to loosen.
Took a look at Tractor Supply my local store doesn't have much for belts and online the belts were mostly 1/2".

Toyed with the idea of cutting an old belt then measuring the gap but wasn't sure how much more to add when the tension spring is added back.

Yes that's how I would install belts on my Model 70. Then rotate the pulley on the deck and the belt would pop right on, but this one is too tight to do that.

What I (obviously) don't understand is the difference between sub frames and mule drives of narrow frames other than some are quick attach.

Since the original engine was replaced with a K301a by a PO could the crankshaft where the clutch attaches sit higher from the frame?
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Your belt should be one of these depending on which deck you are running according to CCC parts lookup.

  • Ref:
    Belt, Mule Drive -38 In. Blade

  • Ref:
    Belt, Mule Drive -42 In. Blade

  • Ref:
    Belt, Mule Drive -48 In. Blade
Does the mule drive lock in all the way? how many holes in the mule drive hitch, some have 2. As for the engine height, then the pto button would not line up.
Thanks Dave. Yes that's the mule drive and sub frame that have. The belt I was trying to install is the 489-397-R3 . Weird huh?
Good point about the pto button. I'll post a picture of the mule drive install later today. Got to drive the Mrs. to a medical appt.
The idler pulleys on your mule drive are not correct as they are too big in diameter. They should be < than 3" Dia., like ~ 2" D. You need to get the correct pulleys to match the odd belt width used on the IH Cub Cadets from the 1X2/3 Series thru the QL models. Part # is

IH 61176 C92 IH 489398 R93 IH 493164 R91 IH 473467 R91.
rrschmitt Thanks for that info. Yesterday I was trying to get part numbers for the deck, and for the idler pulleys I came up with the IH493164-R91. Trying now to find out what size they are. The idlers that came with tractor from the PO measure 3".
Your mule drive and mower look very much like mine, which is a 44" mower, and I have all the same pulleys, 5" driven on the mower and 3" idlers on the mule drive. My tractor came with a box of belts the PO must have used and tried for the mule drive to the mower alone. There were also others for the deck and tiller but it was confusing trying to find the correct belt. That and part number searches have many variables such as type of deck, mule drive, models etc. The one thing that threw me off was the belt section. Everyone mentions the OEM as 3/8" but a belt checker shows it closer to an automotive/ag belt of 13/32. The 3/8 I've tried local ran too deep in the pulleys and I could never get a correct length and tension. I went to Charlie's CCC Spec and finally nailed the correct one. It's listed as 3/8 X 79 but it is actually a tad wider in section than locally sourced 3/8 belts. Anyway to sum it up for whatever reason the 117465C1 belt was my perfect match. That flopping spindle you mention is worrisome and probably a big factor in your belt dilemma. Without stable and secure center distances in a drive system, belt length is a crap shoot.

I would fix that deck spindle, may all of them while you're in there. Keep the 3" idlers. Smaller turn radiuses flex the belt more, add more internal heat to the belt and shorten life for the long haul.

Installing my belt is easy since I made a tool to push the spring idler back as far as it will go. Then with the adjuster pulley all the way loose the belt slips over all pulleys quite easily. The hard part is getting my hands to loop the belt over the PTO but I'm figuring that out with practice. The tool is a piece of flat bar with two notches. One on the end to center on the idler pulley shaft and the other on the side to hook the bar to the frame.
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