How to Adjust a John Deere Drive Belt?

Determining Whether Adjustment Is Required

The transmission drive belt may or may not need an adjustment. Press down on the John Deere lawn and garden tractor's accelerator pedal with your hand just until the pedal starts to stiffen, becoming harder to press. Measure the distance from the bottom of the accelerator pedal to the accelerator pedal floorboard hole's back edge closest to the operator's seat. If the measurement from the bottom of the accelerator pedal to the accelerator pedal floorboard hole edge is less than 1 1/2 inches, then no transmission drive belt adjustment is required. Adjust the riding lawnmower transmission drive belt idler arm if the distance from the bottom accelerator pedal to the accelerator floorboard hole edge is greater than 1 1/2 inches.

Checking Drive Belts

1. Lower mower deck to the lowest setting.

2. Check belts for wear and damage.

3. Clean drive belt area with water or air pressure.

If drive belt needs to be replaced,

Locating the Belt Adjustment Components

The mower deck must be removed to gain access to the transmission drive belt idler arm. After you remove the lawn and garden tractor's mower deck, locate the transmission idler arm under the left side of the lawnmower's frame, just in front of the left rear tire. The transmission drive belt idler arm has two bolts in it, but there are a total of three holes, one of which is an adjustment bolt hole that doesn't hold a bolt. The transmission drive belt idler arm adjustment bolt hole is at the front of the transmission drive belt idler arm, next to the front of the transmission drive belt idler arm bracket.

Adjusting the Belt

The procedure to adjust the transmission drive belt begins with unscrewing the transmission drive belt idler arm bolt that is the farthest from the transmission drive belt idler arm bracket, using a combination wrench for the task. Pull the bolt from the top of the transmission drive belt idler arm bracket. Loosen the center bolt on the transmission drive belt idler arm, but do not remove it. Holding the top of the center bolt-head with the combination wrench while loosening the retaining nut on the underside with a socket wrench is the next task. Push the idler arm forward to align the adjustment bolt holes. Slide the previously removed bolt through the idler arm adjustment bolt hole from the top side down, and thread the retaining nut onto the bolt by hand. Hold the top of the bolt head with a wrench while tightening the nut on the bottom with a socket wrench. Tightening the transmission drive belt idler arm center bolt locks in the new position.

Checking and Adjusting Drive Belt Guides (SX85)

1. STOP engine.

2. Park riding mower on a level surface.

3. DO NOT engage park brake.

A -Nut

B -Front Belt Guide

C -Jacksheave

D -Nut

E -Rear Belt Guide

F -Tab

G -Belt GuIde (Variator)

H -Variator Bracket

4. Using a hoist or safe lifting device, lift rear wheels off surface.

5. Loosen nut (A) under axle to adjust front belt guide (B).

6. Do not push on jacksheave (C) when moving guide to primary drive belt. Make sure there is 1.6-3.2 mm (1/16-1/8-in.) clearance between top of front guide and jacksheave.

7. Tighten retaining nut and check adjustment.

8. Loosen rear belt guide retaining nut (D).

9. Slide rear belt guide (E) rearward to end of slot.

10. Adjust rear belt guide to within 1.6-3.2 mm (1/16-1/8-in.) of the traction drive sheave (upper) portion of the jacksheave.

11. Tighten retaining nut and check adjustment.

12. Tab (F) of variator belt guide (G) should be contacting variator bracket (H). Guide should be parallel to side and top of belt, but not touching belt.

NOTE: Variator belt MUST BE tight when adjusting.

13. To attain proper adjustment, it may be necessary to bend guide.

14. To verify adjustments, operate riding mower after adjusting guides.

Testing the Belt

After you install the mower deck under the lawn and garden tractor's frame, start the tractor and drive it in a large, safe area to test the transmission drive belt adjustment. Push the accelerator pedal forward to engage the transmission forward; release the pedal to allow the tractor to come to a complete stop. The tractor must to come to a complete stop when you release the accelerator pedal. If it does not stop when you release the accelerator pedal, then pressing the brake pedal fully and turning the ignition switch to the "Off" position is necessary. Adjust the transmission drive belt idler arm back to the original position until the transmission drive belt wears and stretches further.