Have you seen this kit from Hustler?
I installed it and what a HUGE difference it made!!
Attached are the instructions and you can see what they did.
Part #123349.
Here is the kit;
Here it is installed on my SD54.
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Check your bolts to make sure they are tight.
The real key is to have the 2 brackets installed correctly. The problem is the hydro's are so powerful they are always trying to twist the mower.
After installing the 2 brackets in my picture. No problems.
If your throwing belts something is not...