Chances are the drive belt needs to be tightened by adjusting the self propel cable. See the owners manual for instructions.

Thanks Roadbike. I'll check the manual.

Checked the operator's manual. It has no section for troubleshooting or instructions how to adjust self propel cable. The only other manual that came with the mower was the Tecumseh engine operator's manual. Do you or other members know how to adjust self propel cable?
Thanks.

According to Toro, there is no adjustment on the self propelled cable or machanism. It's possible that the belt has worn and/or stretched, and the cable isn't able to pull it tight anymore.

The 20017 was last made in 2006, so it's possible that your drive belt has worn and needs to be replaced.

Thanks ggoyeneche. The cable is very loose; however, the rear wheels still turn. Doesn't that indicate the cable still works? If I have to replace the drive belt can I do it myself? I'm fairly handy.

The first thing to do is to check the free play on the sliding handle - the Toro site says yours is Personal Pace, which means that the drive is engaged as you push off with the mower. With the engine off, push the handle down like you want it to drive, and see how far it moves before you feel resistance. About an inch is adequate - more than that requires a cable adjustment. Look on the LH side of the primary handle and find the drive cable anchor with a bolt holding it to the handle. Loosen the bolt which also serves as a clamp - push about an inch of the drive cable housing up and out of the clamp, and tighten it. See if this tightens up the drive. If not, move it the other way - I don't remember which way is right. If you get it too tight, the mower will be hard to pull back with the engine running - this is why you need the free play in the handle.
Now, let's say you reduce your free play but it still doesn't drive any better - then you have to replace the drive belt and/or inspect the whole driveline for worn-out pullies or packed clippings interfering with proper operation. In use, the gearbox tilts back to tighten the drive belt. The belt is designed to constantly slip. The only way to fully engage it is to hold the cross bar with one hand and push down hard on the sliding handle. This will usually spin the wheels and the mower will take off at about 15 MPH! I just mentioned that in case you notice the belt slipping and think something is wrong.
There are a few more things that could be wrong with it, including a worn-out gearbox or dirty/non-lubricated axle-end gears/ratchets.

Thanks Saxman. I'll follow your advice and see if make the adjustments to get the mower to self propel. If I can't do it I'll take it to a repair shop. No fun mowing uphill without the benefit of self propel.

I loosened the clamp on the left and pulled the cable up
about an inch and retightened. Tried it out and looks like it's moving forward a lot better. Thanks to you all for your help.

I have a 21 inch Personal Pace Toro that seemed to be going slower even at the close of last season. Now in June 2011, the belt jumped off the back pully on the rear axle.

After 3 hours spent to get the belt back on the pully, - I noticed that over the year the belt must have stretched some, - because there was way to much slack in the Personal Pace cable.

There is no adjustment to tighten this cable, - and I'm not going to buy a new belt every year. So to 'tighten' the cable, I removed the top plastic protective cover behind the engine. Removed the tension spring from the transmission and the plastic hold-down to the chassis.

The termination of the cable is a steel or lead ball on the cable within the spring. I found some of the smallest nuts (as in bolts) that I could find, - clipped one side of each with wire clippers so they looked like a 'C', slipped the 2 of them on the cable above the termination ball. I pinched the nuts shut so they wouldn't come off the cable.

Maybe next year I'll have to add a 3rd nut.

Boy, do I feel dumb. I thought it was just age as my mowing became more difficult. One super hot summer and I've been pushing my Toro personal pace mower without realizing it. On the left side of the handle is a nut and plate securing the cable, loosened the nut, pulled the cable down about and inch and zoom...personal pacing again. I found that as you push the slide down you notice it engaging the transmission only when pulling it backwards. Followed the directions above about leaving a little slack before it engages and just cut my yard for the thousandth time this hot summer in half the time. Thanks for the advice, great forum

I followed the instructions below on my 2011 Personal Pace mower, and it worked like a charm. It was failing to pull itself up even a small grade but after simply loosening the cable holder nut on the side of the mower handle, moving the cable down about an inch and retightening the nut, the self-propel function was much better. Saxman1, thanks so much for the tip. It saved me $60 in mower diagnostics fees at the local shop.

Saxman, thanks for the tip. I loosened the cable and actually pushed it down about and inch and the mower
is now back to "personal pace' status.

The rear wheels on my Toro Personal Pace mower model 20017 will not turn. I don't know what is wrong. Any suggestions would be appreciated. Thanks

My Toro mower will only run when I keep primer bulb pushed in, any suggestions?

I know this is an old question, but since I recently had the same problem I wanted to share the solution I found with everyone. I was also having problems with my rear left wheel, the gear kept getting stripped out after about 30 minutes of use. I went through 3-4 wheels before I found the true problem. The wheel is mounted to the body/frame of the mower, which is just sheet metal. From mowing sideways across the face of hillsides the mower's weight all goes onto the lower back wheel, and after a year or two of use the body/frame has bent. Now the wheel is not square with the drive shaft/pinion. This causes the gears to not mesh properly and the wheel gear to strip out. I bent the frame back then welded some 1/4" plate to the inside of the body/frame to stiffen it up. Since then the self propel system is working great.

My back wheels lock up when I try to back up. Any ideas?

23 year old elect start rear drive 22" toro. Was top of the line.
Runs good but has a repeating 3 group high pitched whistle
during operation. This is a new problem. Is engine warning me of a deficiency? Oil is OK according to dip stick..

@Saxman you saved my day and definitely money with your suggestion. It worked and my mower operational again. Thank you a lot.

My Toro AWD #20353 has a different problem. I cannot stop the rear wheels from pulling. This just started happening and is very annoying. I've tried adjusting the cable to no avail. ?

Thanks, Tom,

I'll check that out. Looking under it I didn't see a second belt.

I figured out the problem. The Front wheel drive belt had jumped down over the rear wheel drive belt on the pulley.