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Okay, I'm officially stumped...got a 2005 Grasshopper 727K that we use with a vac and hopper system for fall leaf pickup. Started out with a slight hesitation in the right wheel after it had been in use a while. Then it got more frequent until it turned into a nearly constant issue. If you take off with any force, the left side tire starts to break free and the right side just loses all power. Was trying to avoid taking it in for service and paying big $$$ but at this point, it probably would have been cheaper.

Did a ton of Googling and found we should start with checking for adequate belt tension. Checked and tension was good, but tightened it up a bit more just in case it was slipping under heavy load or something. Problem remained unchanged.

Next step of Googling and troubleshooting convinced me it was the wheel motor and not the transaxle so $700 later, the wheel motor was replaced along with fluid (Mobile DTE 26) and OEM filter. It ran strong for an hour or so and I thought it was fixed, until I got it good and warm and boom. Nope. Problem unchanged.

Welp, $700 wasted only to dump another $700 into a transaxle. That's all that's left.........or so I thought?

Put a new transaxle in it. OEM replacement. That was a "fun" job, but looked easier than trying to rebuild it. Replaced fluid and filter again. Again Mobile DTE 26 and OEM hydro filter. Just pulled it out of the barn and took it for a spin to bleed the air out, check for leaks, and see how it runs.

Problem. Once. Again. Unchanged.

What is left? What am I missing? Any ideas?

It's only the right side. The left wheel has plenty of torque and no hesitation whatsoever. If I'm sitting at a dead stop and quickly shove the lever fully forward on the right side, the wheel will just begin to spin a little and suddenly stop. If I leave it there and just sit, about 5 seconds later, it'll finally take off. I also had jumpered the seat switch and stood there operating it with the seat tipped so I could watch the belts, I didn't notice any belt slippage while the wheel was refusing to move. Any help figuring this out would be awesome.

Update: While waiting for ideas, I decided to tear things apart and replace the belts since I had bought new ones to do when I did the transmission...avoided it since it was more to disassemble and I had ruled it out as the problem. Old belt looked fine and tension was tight but the belt must have been stretching out under load or glazed up because it spins that tire just perfect now.

So.... roughly $1500 wasted and lesson learned...ouch.

If anyone experiences weakness in the hydros, don't just check the belts. CHANGE them. lol

What type of hydro trans were they.??
Some I hear aren't even available anymore..

Unfortunately a lot of problems are over diagnosed and some basics are missed, it happens, I just hope that the spares you now have will fix the next problem you get in 5 years time! And whilst you should only use CRC belt grip ( or others) for diagnosis, not a fix it all, it is a good product for various belt driven items when testing. Just ensure you then scrub all pulleys clean with solvent before putting new belts on.

blackshirej said:

Update: While waiting for ideas, I decided to tear things apart and replace the belts since I had bought new ones to do when I did the transmission...avoided it since it was more to disassemble and I had ruled it out as the problem. Old belt looked fine and tension was tight but the belt must have been stretching out under load or glazed up because it spins that tire just perfect now.

So.... roughly $1500 wasted and lesson learned...ouch.

If anyone experiences weakness in the hydros, don't just check the belts. CHANGE them. lol

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You replaced the wheel motor - how about the hydraulic pump driving the motor?
Is it the same pump for both left & right wheel motor, or do they each have their own pumps?

On mine each wheel have their own hydraulic oil pump & motor.

Sounds like you may need to take it to someone who is familiar with these HST drives!

I bought used 721D back in 2003 from a commercial user, and now have about 1700 hours on the meter - I've changed HST fluid & filters twice so far.
Hoping the previous owner did oil the changes by the book, but it's been 18 years with a used hopper so far!