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3K views 7 replies 5 participants last post by  TAHOE 
#1 ·
I have owned a Craftsman 42" 21HP lawn tractor since 2010; Model 917.28922. In addition to cutting grass, I use it in the fall to mulch leaves so they deteriorate more quickly. The last two times out to mulch, the temperature has been low and the transmission has been very sluggish. I could not seem to get the tractor to go faster than a snail's pace. The mower blade performance was fine. Is there a problem with my motion drive belt? Or is there another issue? If it is the motion drive belt, can I reasonably replace this myself?
 
#2 ·
From the operators manual:

"Before driving the unit in cold weather, the transmission should be warmed up as follows:
1. Be sure the tractor is on level ground.
2. Place the motion control lever in neutral. Release the parking brake and let the clutch/brake slowly return to operating position.
3. Allow one minute for transmission to warm up. This can be done during the engine warm up period."

Of course it could be a slipping drive belt, but I think that would squeal. The drive belt runs from the engine pulley over one or more idlers (one tensions the belt with the clutch/brake pedal) and to the transmission. Make sure it's snug (with brake released) and in good condition. Look for signs of glazing.

Assuming you've done that the transmission might be on its last legs. Mine got to where it didn't really want to move (I don't recall it being temperature dependent) and I extended the life by replacing the transmission oil. It was starting to act up again when I got rid of it.
 
#5 ·
I think JiminRI may have hit on the real culprit. I had this issue a couple years ago also when mulching. It went away. Normally nothing "goes away" like that. But it might have cleared itself of debris. I was planning for the annual self-tuneup and winter shutdown procedure in the nexty couple of days. I'll have to track the brake/clutch release point to see if there is junk. Normally I scrape the under-deck of clinging dried grass but i will look all around the underside.
 
#7 ·
Hey. I worked out the transmission issue. Yesterday I was doing a delayed winterizing on the Craftsman, oil change, etc., etc. I also wanted to dive into some of the suggestions forum members have made about my problem. I started her up and nothing - no forward or reverse. I cleaned out as much as I could of the residue of leaves possibly impeding free operation of the drive belt - at least as much as I could without removing the mower deck. Still no movement. On a whim, instead of simply releasing the brake with my foot, I forcefully pulled back on the foot brake with my hand, and the tractor sprung into forward motion. Reverse also worked. All forward and reverse speeds appeared normal. I turned off the tractor to see if this was a fix, or if I needed to yank on the release each time. Thankfully, the tractor moved with only the normal release of the brake. Back to normal.

My conclusion: When I mulch leaves I sometimes take too large of a "bite" and the leaves get jammed everywhere under the unit, impeding proper operation of the pulleys and the belt associated with the drive. This situation has only happened twice in the 7 year history of this tractor; and both times it was when I was dealing with heavy leaf mulching.
 
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