HOW TO ADJUST THE CUTTING BLADE TENSION OF THE MOWER BELT.

1. Disconnect the spark plug wire at the front of the mower, siphon any excess fuel from the gas tank and verify that the oil dipstick is securely fastened to avoid oil leakage.

2. Remove the screw located on the side of the mower deck, next to the right rear tire, then tilt the mower onto its side so the air filter is facing up.

3. Unfasten the blade retention bolt. The blade retention bolt is located in the center of the blade. Slide the blade off the mower.

4 Unfasten and remove the screws holding the engine baffle to the mower deck, then remove the baffle. The baffle is the circular piece located beneath the blade.

5. Remove the screw fastening the belt cover to the mower deck. Remove the spring between the belt cover and transmission pulley, then remove the belt cover to expose the belt.

6. Adjust the belt to the desired tension by manipulating the engine and transmission pulleys. If the belt has become slack due to age, you need to replace it. To remove it, slide it off the engine pulley first, then slide it off the transmission pulley.

7. Replace the removed items in reverse order.

How to adjusted Cutting Deck Belt Tension

You do not say which size cutting deck you have. I will be writing about the 48", 3 blade cutting deck

The belt on this deck is self tensioned. The tension is provided by a spring attached to a moveable pulley on the deck. When the belt is in place you can manually force this pulley forward/backward and it will release the tension.

If the belt is off track, place the belt back around all the pulleys in the correct path, lastly force this spring loaded pulley forward/backward (depending on your deck, the direction is not important, the tension is) to get the belt around the pulley. If the belt is placed correctly, when you release the spring loaded pulley it will properly tension the belt.

Typically, these belts should not be jumping off. If yours is coming off frequently the belt may be worn. When they wear they get quite a bit longer, then the tension pulley cannot apply the correct tension. Rarely does the tension spring have to be replaced.

The other problem that causes belt jumping is worn spindles and stationary pulleys. The spindles are the most likely to need replacement. You can buy excellent replacements for JD spindles on Amazon for very reasonable prices. The following spindles are super replacement spindles for the 48" deck. They may very well be the same for smaller and larger decks; I have not researched that. Just search Amazon for Silver Streak # 285851.

Silver Streak # 285851 Spindle Assembly for JOHN DEERE GY21098, JOHN DEERE GY20962,

Product description:
Spindle Assembly / John Deere GY21098 Pack Size:1 JOHN DEERE GY21098, JOHN DEERE GY20962, JOHN DEERE GY20867, JOHN DEERE GY20454 OREGON 82-359, ROTARY 12910, ROTARY 11964 JOHN DEERE D100, D110, D130, D140,D150,D160, LA100, LA105, LA110, LA115, LA120, LA125, LA130,LA135, LA140, LA145, LA155, LA165, X110, X120, X140 Includes grease Zerk, pulley lock nut, blade lock nut, and washer , Height: 7 ", OD: 5 "

You can also find replacements for the flat pulleys on Amazon. If you cannot find what you need there, go to http://www.greenpartstore.com//

Sounds as if the deck belt is stretched. Replace the belt and make sure it is routed correctly. When the belt is off of the unit, make sure each blade assembly rotates without resistance. One of the mandrel assemblies could be seized.

Assuming you have put the blade drive lever into 'disengage' check the blade drive belt tension. With blade disengaged, belt should have significant slack. You may need to adjust the control cable, adjustment is usually on the mower deck; or you may have some debris on the deck preventing the pully to release belt tension

follow this steps and fix it. GOD BLESS YOU
If grass is poorly or unevenly cut, try mowing at a slower speed and adjusting the engine speed with instructions in your owner's manual. Scrape away any dried grass and other debris caked under the mower deck. Sharpen or replace dull or bent blades . Check and replace a worn belt.
If the V-belt slips or comes off during use, clear any debris in the belt area, adjust the drive-belt tension (see below), or have the belt replaced. Adjust and tighten pulley fasteners or have a service center replace worn parts.
If the belt squeals or wears excessively, adjust the drive-belt tension (see below) and look for obstructions around the belt. If that doesn't work, take the mower in for professional service.
If the mower vibrates excessively when the clutch is engaged, scrape away any debris accumulated under the deck. Balance the blade and replace the blade if needed. If that fails, adjust drive-belt tension (see below). If you find that the drive belt, pulley, or other belt-drive part is damaged, consider having it replaced by a professional.
If the mower is hard to shift or doesn't move when the clutch is engaged, adjust the drive-belt tension (see below). Also make sure the mower is lubricated according to the owner's manual specifications. As needed, have the mower serviced for damaged or maladjusted clutch/brake pedal linkage.
If the engine doesn't start, loses power, or dies during use.
Replace a recoil starter rope:

1. Disconnect the spark plug cable for safety.
2. Disengage the throttle cable from the housing and remove the housing as needed to access the starter.
3. Remove the handle from the rope, which is often held in place by a knot or retainer pin.
4. Unfasten the other end of the rope from the starter using pliers or a cutter as needed.
5. Knot the end of the replacement rope.
6. Tighten the pulley counterclockwise all the way, then back it off two turns and hold it firmly.
7. Thread the unknotted rope end through the pulley hole.
8. Thread the rope through the housing hole and pull it taut.
9. Slowly release the pulley, allowing the rope to wind around the pulley.
10. Attach the handle and reassemble as needed.
11. Reconnect the spark plug cable.

Replace a recoil starter spring:

1. Disconnect the spark plug cable for safety.
2. Remove the housing and the spring cover.
3. Carefully remove the rope from the pulley to release spring tension.
4. Remove and replace the spring as recommended by the manufacturer.
5. Reinstall the pulley, rope, and housing following the instructions above.
6. Reconnect the spark plug cable.

Sounds like a loose belt check the tension spring if they ok check and see if belt is strectched

it needs to be tighter,i dont no if it needs a belt or tension adjusted i would need to see the mower myself

I have the same problem same year, same model. I changed the drive belt and it still won't go up steep hills that it used to easily climb. I don't see any way to adjust tension and it doesn't cover that in the operator's manual. What did you find out with yours?

For removing/replacing the deck belt, the general method is:

1. turn off engine, remove key and set parking brake
2. disengage blade by putting blade engage lever into off (disengaged) position
3. lower the cutting deck to the lowest position (closest to the ground)
4. relieve the belt tension (depending on the model, use a 3/8 inch ratchet set to tighten in the square hole of the idler bracket)
5. remove and replace the belt

NOTE: it's not necessary to completely remove the cutting deck.

Useful diagrams for removing the cutting deck, http://216.213.143.2/ProAuthor/ManProc.cfm?ManualID=425&ProcID=14794

For deck belt diagrams, http://216.213.143.2/ProAuthor/ManProc.cfm?ManualID=425&ProcID=14796

If the transmission drive belt needs to be replaced, several components must be removed and special tools (i.e. air/impact wrench) used in order to change the tractor's transmission drive belt. See an Authorized Toro Service Dealer to have your drive belt replaced.

check for a broken belt tension er or maybe grass clippings under belt area, check for a broken or loose pulley bearing, even a bent shaft on the deck.