Quick answer
Most “hydraulic” problems on a Toro zero-turn (TimeCutter, Titan and similar) involve the hydrostatic drive. Symptoms are a mower that’s weak or slow, pulls to one side, loses power when hot, or won’t move. Check the easy things first: the bypass (tow) levers fully engaged, a slipping or broken drive belt, tire pressure and tracking. Then check the oil level and condition on serviceable transmissions, and look for air in the system after service.
Toro’s residential zero-turns use two hydrostatic transmissions, one per rear wheel. Many TimeCutter models use sealed units with no routine fluid service. Higher models (some Titan and commercial machines) have serviceable units with expansion tanks and filters.
Symptom guide
Won’t move at all
Bypass levers in the push position, a broken or off drive belt, or a parking brake that’s stuck on.
Weak, slow on hills
Slipping belt, overheated transmissions, low or old oil (serviceable units), or internal wear.
Pulls to one side
Uneven tire pressure, tracking out of adjustment, or one transmission weaker than the other.
Fine cold, weak hot
Blocked cooling fins or fans, thin or old oil, or worn pumps.
Jerky after service
Air in the system. Purge it as the manual describes.
Step 1: Check the bypass levers
Each transmission has a bypass (tow) lever or rod for pushing the mower by hand. If either is partly in the push position, that side loses drive. Set both fully to drive.
Step 2: Inspect the drive belt
With the engine off and the key removed, check the pump drive belt for wear, glazing, cracks or a weak idler spring. A slipping belt mimics a failing transmission.
Step 3: Tires and tracking
Set both rear tires to the same pressure. If it still drifts, adjust the control-lever tracking per the manual so both sides run at equal speed with the levers fully forward.
Step 4: Cooling
Clean grass and dirt from the transmission cooling fins and fans. Hydrostatic units lose power as they overheat.
Step 5: Oil and purging (serviceable units only)
If your model has expansion tanks, check the level cold, and change the oil and filters at the manual’s interval with the specified oil (often 20W-50 on Hydro-Gear units). After service, purge air by working the drive slowly forward and back as the manual describes. See our hydrostatic oil fill guide.
Step 6: When it’s the transmission
If the belt, bypass, tracking, cooling and oil all check out and one side is still weak, the pump or motor may be worn. Sealed units are usually replaced rather than rebuilt. Compare the cost with the mower’s value, and use a Toro dealer for warranty units.
Frequently asked questions
Do Toro TimeCutter transmissions need oil changes?
Many TimeCutter models use sealed transmissions with no routine fluid change. Check your manual for your exact model.
Why does my Toro zero-turn lose power going uphill?
Most often a slipping drive belt or overheated transmissions. Clean the cooling fins and check the belt first.
Related: Toro rear-wheel-drive problems · Hydrostatic riding mowers · Hustler vs Bad Boy
Sources and method: Based on Toro operator-manual guidance and Hydro-Gear service practice for zero-turn transmissions. Follow your manual for your model’s specific procedures and fluids.
Update log: November 2026: rewrote the guide. We added a symptom table, ordered checks (bypass, belt, tracking, cooling, oil and purge), sealed vs serviceable notes and an FAQ.