Cub Cadet ZT1 Or ZT2 Drive Belt Keeps Slipping? Here’s the Real Fix

kowerko
Jul 31
3 min read

If your Cub Cadet Ultima ZT1 or ZT2 zero-turn mower keeps throwing or slipping the drive belt, you’re not alone. A customer recently brought in their ZT1 with a belt that was off-track and cracked—and this wasn’t the first time it happened. These models are known for premature belt issues even with low hours.

In this post, I’ll walk you through the step-by-step repair process we use in our shop, including replacing the drive belt, swapping a noisy idler pulley, and—most importantly—modifying the spring tension to prevent future problems.

Watch the full repair video on YouTube for a complete walkthrough, or scroll down for the breakdown.

Step 1: Drop the Deck & Confirm the Issue

Start by lowering the deck fully—set the height adjustment knob to the lowest setting. If your mower won’t move, confirm the hydro bypass rods are disengaged. These rods must be down and latched to engage drive mode (there’s one on each side near the rear wheels).

From underneath, verify the drive belt is off. Be sure not to confuse it with the deck belt—this repair targets the upper drive belt near the engine and hydros.

Step 2: Remove the Belt and Inspect the Damage

You’ll want to:

Use a spring puller (or a modified wrench with a notch cut out) to remove the tension spring from the idler arm.
Disconnect the PTO clutch wire by pinching and pulling the clip.
Roll the drive belt off by rotating the pulleys slowly—avoid pinching your fingers.

Remove the anti-rotation bracket (½" bolt) holding the clutch, then fully remove the belt. This gives access to the idler pulley for replacement.

Step 3: Replace the Idler Pulley (Optional but Recommended)

If your pulley is making noise or shows signs of wear—especially grooves or a damaged bushing—replace it. Use a 9/16" socket and a wrench to remove the pulley bolt. Install the new pulley using the original bushing, washer, and nut.

We strongly recommend replacing this if your belt has come off multiple times.

Step 4: Install the New Belt and Fix the Tension Problem

Route the new belt:

Around the engine pulley
Around the right hydro
Across the front to the left hydro
Under the idler pulley

Check for debris—sticks, rocks, or buildup can easily derail the belt.

Now for the critical fix:

By default, the tension spring mounts to a hole that provides very little tension. This design flaw leads to slippage and premature belt wear.

Our fix:Relocate the spring anchor point further back—hook the spring into the arm like normal, but attach the rear side to the rear corner hole behind the battery tray (not the default notch).

This dramatically increases tension and eliminates belt slippage.

Step 5: Reassemble and Verify Proper Tension

With the belt routed and spring modified:

Reattach the PTO clutch wire
Reinstall the anti-rotation bracket
Spin all pulleys to ensure smooth rotation
Check that the belt sits inside all keepers and grooves properly

Start the mower and engage the transmission—your belt should now stay tight and properly aligned.

Final Result

After implementing the spring relocation, the Cub Cadet ZT1 ran flawlessly with no belt slippage—even under load. This method has worked on every ZT1 we’ve serviced with similar issues, and we’ve never had a customer return for the same problem.

Watch the Full Repair Video

Watch on YouTube to see exactly how we:

Remove and replace the belt
Swap a bad idler pulley
Modify the tension spring
Prevent future belt failures

Pro Tip

If your belt keeps coming off, it’s usually not just wear—it’s lack of spring tension. Always inspect the idler arm, pulley bushings, and spring tension if you want to avoid repeat issues.

Frequently Asked Questions (FAQ)

Q: Why does the drive belt keep slipping off my Cub Cadet ZT1?

A: Worn idler pulleys, low spring tension, or cracked belts are common causes. Debris stuck in pulleys can also derail the belt.

Q: Can I use an aftermarket belt on a Cub Cadet Ultima ZT1?

A: Yes, but OEM belts provide the best fit and durability. Aftermarket belts may work, but often wear out faster or slip under load.

Q: How do I increase tension on the drive belt?

A: Relocate the spring anchor to a further rear hole behind the battery. This provides the tension needed to prevent slipping.

Q: What tools do I need for this job?

A: A spring puller or modified wrench, 9/16" and ½" sockets, ratchet, and a flathead screwdriver.

Q: How do I know if my idler pulley needs replacing?

A: If it squeaks, grinds, or has visible bushing wear, replace it to prevent belt damage and improve drive performance.