3 Must Know Gravely Zero Turn Mowers Hydraulic Problems (Solution Added!)

Last updated: February 24, 2026

Gravely, as a successful brand has been serving the tractor industry for a long time. But consumers do face some obvious problems and issues, which can be a bit technical. You might think how hard that will be?

There is not much to worry about. I have gathered some of the problems and briefly described the solution in the article accordingly. 

Here I have decided to discuss some of the common issues that you might face with Gravely zero turn hydraulic mowers. 

Verdict

Gravely always tries to deliver the best features within a really good budget. They are quite popular for the quality products they offer. But there are always limitations to the technical products. You never know what’s coming for you. 

However, some problems are pretty basic and can easily be resolved. I have discussed some of them in the article. You can also contact the gravely support teams, they have a good response rate on that too.

Related Posts:

Key Takeaways

• Gravely zero-turn hydraulic problems most often involve low fluid, contaminated fluid, or air in the system
• Purging the hydraulic system (disengaging the bypass valves and moving the levers) often resolves air lock issues
• Always use the manufacturer-specified hydraulic fluid — mixing fluids can damage seals and pumps
• Drive shaft and belt condition affect hydraulic pump performance — inspect these during routine maintenance
• Hydraulic filter replacement every season prevents many problems before they start

Frequently Asked Questions

How do I purge the hydraulic system on a Gravely zero-turn?

Air in the hydraulic system causes erratic or weak drive behavior. To purge: With the mower on level ground and engine OFF, locate the bypass valve(s) — typically red knobs or levers behind the rear wheels. Open the bypass valves (usually turn counterclockwise). Push the drive levers forward and backward several times to manually purge air. Close the bypass valves. Start the engine and let it warm up at idle for 5 minutes. Gradually operate the drive levers through their full range. Repeat if movement is still erratic. This process is also needed after replacing hydraulic components or if the machine has been stored long-term.

What hydraulic fluid does a Gravely zero-turn use?

Most Gravely zero-turn mowers use a 20W-50 motor oil or specific hydrostatic transmission fluid (check your model’s operator manual for the exact specification). Common fluids used include Mobil 1 20W-50 synthetic motor oil or dedicated hydrostatic fluids like Hydro-Gear’s fluid. Never substitute with standard transmission fluid (ATF) unless your manual specifically permits it. Check fluid level when cool and with all cylinders in normal operating position. Overfilling can cause foaming, which introduces air into the system.

Why does my Gravely zero-turn pull to one side?

Pulling to one side while driving straight is one of the most common zero-turn complaints. Causes include: Unequal hydraulic pressure between the two drive pumps (often fixed by adjusting tracking — see operator manual); air in one side of the hydraulic system (purge as described above); different tire pressures (check and equalize all tires); worn or slipping drive belt on one pump; damaged or worn hydrostatic pump on one side. Start with the simplest solutions (tire pressure, purging) before moving to more complex diagnostics.

Related guides: lawn mower not getting fuel, Cub Cadet 6284 common problems, and best lawn aerators.