Commercial 40 Mower- Spring Replacement - - The Friendliest Tractor Forum and Best Place for Tractor Information
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post #1 of 3 Old 09-23-2019, 09:27 AM Thread Starter
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Commercial 40 Mower- Spring Replacement

If your deck suddenly loses ~50% of cutting capacity, and it's not a belt, then it's likely a broken spring.

The Gravely part has superseded to: 08353300

The instructions in the Operator's Manual are pretty good, but:

1. Yes, you have to remove the mower attachment from the Gravely and then split the drive unit from the deck.

2. After splitting the two mower components, "gently" raise slightly the drive unit, and turn it clockwise 90o. You can now access the spring attachment points.

3. The belt pops off the Rotor Pulley with a screwdriver, and is re-attached by simply inserting it into the sheave slightly and rotating the Rotor Pulley. Easy-peasy.

4. The spring puts up some fight, but with the belt off the Rotor Pulley it's just some fiddling around with the two attachment points. Use the existing spring as your guide on location for installing the new spring.

5. Flip the deck vertical, to ensure that the 3in carriage bolts absolutely seat into the deck. You need a 3/4 and a 9/16 socket for the two carriage bolts and the three nuts.

6. When vertical, now is a good time to clean the deck of old clippings- for guys with the older style of deck without the side discharge, maybe a good time to mortise/grind a discharge port into the deck?

I thought about installing an eye bolt to make re-attachment of a broken spring easier in future. Then I thought, "I'm not smarter than the Gravely Engineering Department" and left well enough alone. KISS


Old and new style decks- the discharge port makes for easier cutting IMO:
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post #2 of 3 Old 09-23-2019, 04:27 PM
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Re: Commercial 40 Mower- Spring Replacement

I never realized that the 40" Commercial originally did not have a right hand discharge. Mine is the later version w/ a discharge but it also came with the factory block-off plate which usually gets lost. I find most times the grass exits out the front right anyway so the side discharge sees very little. Regardless, it does cut smoother and better than the 30" single blade unit.

The springs on mine were totally junk so I just went to TSC and got two springs close to the original, added a repair chain link to the anchor hole and installed. I think they are tighter than the originals but they do hold the belts well under control. Still having issues with the belts dragging/wearing but have just got a set of 18" tall tires so the mower will set level/flatter and not lean backwards like it does with the 16" tires.
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post #3 of 3 Old 09-27-2019, 07:32 PM
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Re: Commercial 40 Mower- Spring Replacement

I worked at a school that had a fairly large campus, and they were constantly having problems with broken windows and dings in parked cars from the side discharge on the grasshopper mowers they were using. I looked online and found they made a rear discharge mower, and that solved the problem, it was used around the buildings and parking lots, the other mowers were used out the open areas.

I bet Gravely already had this figured out way back when those old mowers were designed.
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