T1400 HST Mower Deck Belt Slipping?

danofresh

New member

Equipment
Kubota T1400 HST
Jul 28, 2026
3
1
3
Brutus, MI
I've been using this mower for quite a while (10-15 years) and love it. A few weeks ago, after a few months of mowing, the mower blades would bog down in even the slightest longer or thicker grass. I noticed that the belt felt really loose even when the blades were engaged. The blade tensioner is about as close as you can get to touching the forward pulley. I've replaced the belt with an OEM from Kubota ($55) and am having the same problem. Is there an adjustment I'm not seeing? The forward pulley and the back pulley don't seem like you can adjust. Again, the engagement pulley is quite literally almost touching the forward pulley. The spring for the engagement pulley appears to be functioning properly. Any thoughts on what I can do?
 

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Bee-Positive

Well-known member

Equipment
BX1880, Cab, FEL, Tooth Bar, MMM, QH, Ballast Box
Nov 16, 2022
993
945
93
Amsterdam, NY
I've been using this mower for quite a while (10-15 years) and love it. A few weeks ago, after a few months of mowing, the mower blades would bog down in even the slightest longer or thicker grass. I noticed that the belt felt really loose even when the blades were engaged. The blade tensioner is about as close as you can get to touching the forward pulley. I've replaced the belt with an OEM from Kubota ($55) and am having the same problem. Is there an adjustment I'm not seeing? The forward pulley and the back pulley don't seem like you can adjust. Again, the engagement pulley is quite literally almost touching the forward pulley. The spring for the engagement pulley appears to be functioning properly. Any thoughts on what I can do?
You've got a 30 year old spring - replace it.
Adjust nuts 150 on rod 140.

Tension Spring.jpeg
 
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MapleLeafFarmer

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Lots incl. B and L kubotas
Dec 2, 2019
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With the belt removed, can you spin all the pulleys, etc.... Freely to let us know if anything seems to be binding?
 

Bee-Positive

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Equipment
BX1880, Cab, FEL, Tooth Bar, MMM, QH, Ballast Box
Nov 16, 2022
993
945
93
Amsterdam, NY
Sorry - I had the wrong model.
Replace springs 120 and 130. Make sure arms 020, 050, and spring plate 125 are not bent.


Tension Spring.jpeg
 
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Russell King

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Jun 17, 2012
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@Bee-Positive and @danofresh

I don’t see that the pictures in post #1 match the diagram. There seems to be a long distance between the upper and lower pulleys in the pictures. Maybe that is between the pulleys on #10 but they look close together in the diagram. But the diagram may not represent reality?

Anyway, I would replace the springs as suggested to see if that helps. You might need to lubricate the pivot point (shaft through all the pulleys) and see if that helps also.
 
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Bee-Positive

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BX1880, Cab, FEL, Tooth Bar, MMM, QH, Ballast Box
Nov 16, 2022
993
945
93
Amsterdam, NY
@Bee-Positive and @danofresh

I don’t see that the pictures in post #1 match the diagram.
Now I'm confused.

My first post (post #4) is the K-Pad diagram for the RC40LT.
My second post (post #6) is the K-Pad diagram for the RC40LT-17 (T1700H).

Either way - as suggested - replace springs and lubricate, least costly first step in solving the issue.
 
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PoTreeBoy

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WestTn/NoMs
I'm not familiar with the T1400. But, pulleys wear also, especially the stamped sheet steel ones. When they do, the wedge action is affected, resulting in belt slippage. I had to replace the drive pulley on my MTD-made mower after 10 years or so.

You can check your pulley with a straight edge on the belt faces. They should be flat.
 
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MapleLeafFarmer

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Lots incl. B and L kubotas
Dec 2, 2019
1,155
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113
E.
I'm not familiar with the T1400. But, pulleys wear also, especially the stamped sheet steel ones. When they do, the wedge action is affected, resulting in belt slippage. I had to replace the drive pulley on my MTD-made mower after 10 years or so.

You can check your pulley with a straight edge on the belt faces. They should be flat.
100%.... with all pulleys, blades, etc.... turning freely OP down to worm pulleys, wrong belt, bad tensioner IMHO...; sure he is well on his way to an easy and fairly cheap fix as he through process of elimination works his way to success.
 
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sdodder

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Kubota 1400H
Jun 28, 2026
14
5
3
New Paltz, NY
I'm not familiar with the T1400. But, pulleys wear also, especially the stamped sheet steel ones. When they do, the wedge action is affected, resulting in belt slippage. I had to replace the drive pulley on my MTD-made mower after 10 years or so.

You can check your pulley with a straight edge on the belt faces. They should be flat.
I've got the exact same machine! I've posted here recently about it and gotten some GREAT advice- I'll be following your progress. Maybe I'll post some pics of MY rig - when it's up and running-

Good luck, Steve