How do you adjust the Forward & Reverse Pedals on John Deere Riding Mower Model GX345

Quester edited for clarity and spelling 'deer' to 'Deere'.
Question moved to John Deere D110.

Try the 5 minute fix, but your sounds like the hydrostatic transmission.

https://www.google.com/search?q=John+Deere+D110+mower+stops+after+5+feet

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Here's the link and I'm sure you will get the solution of your problem.
JOHN DEERE LX255 LX266 LX277 LX277AWS LX279 LX288 LAWN GARDEN TRACTOR...

I have ran into this before. It's time consuming to fix. You have to pull the body of the mower loose and take the pedal completely apart. Clean it and grease it then put it back on, it will work fine then. They need to put grease fittings on those pedals.

Sounds like the transmission needs work if you've replaced the belts.

Err 03 Reverse Pedal. Voltage signal out-of-range or not calibrated. Machine does not drive. Contact your John Deere dealer.

Sounds like new belt is jammed or something is out of place. Turn by hand and find out where the problem is. You can tell where the belt is stuck or jammed. Pull the key before you mess with stuff underneath the unit. I installed my belt the wrong way on my unit and ruined a new belt and it would not shift.. The shifter rod could have been dislocated when you installed the belt also.

this hydrostat drive tractor is designed to max at 5.5 mph forward, 2.5 in reverse, check linkage at pedal if you dont think your achieving those speeds

Go to youtube . Type in your make and model/ forward and reverse will not engage. Should be helpful.

Hi, most likely the brakes are hanging up. Follow the brake pedal path to the rear of the mower, it is attached to a small arm on the side of the diff that is probably locked forward. This lever and the pins behind it need to be freed up so the lever operates forward and backward freely when the brakes are applied and released. Hope this helps, regards Phil.

hydrostatic transmission has reached the end of its life. Call a dealer and get a price to repair, then contrast that amount with the cost of a new mower. Those transmissions are not cheap, you may find folks selling them NOS on eBay, certainly worth a few minutes googling around before you lay down the bucks. Do not buy a used transmission.