Variable sheave pulley transmission.

Donman · Jul 7, 2009

I just came into this Yardmachine lawn tractor real cheap ($1) from a guy who just wanted rid of it. It has 4 wheel steer and a variable pulley transmission. The lever on the right fender switches from neutral to either forward or reverse and the lever on the left fender is for forward or reverse speeds 1 to 7. All the left lever does is change the position of a variable double sheave pulley and thus change the ground speed. My dad's JD 110 had this setup along with a 3 speed transmission. This looks like an effort to make a transmission on the cheap. Does anybody have experience with this set up? Do you get enough speed change to make this worthwhile?

Bedlam · Jul 7, 2009

Not sure ,I know enough to answer your question but the price was a bit high I would have bargained for .99 cents myself

Im sure someone with the knowledge will ring in here.

Redneck in training · Jul 7, 2009

While ago some cars (now defunct DAF comes to mind) with small engines used to have such transmissions. Power planst used to control speed of feeder of coal to the boiler with them etc. That is all history now due to variable speed electric drives replacing mechanical solution. Such transmissions are still used in small scooters.
So it should work quite reliably for small power lawn tractor.

geneP · Jul 7, 2009

I have a MTD made mower with that transmission. Use the gear selector to set it at the max speed you want to mow. Use the clutch pedal to vary your speed down to 0. It's a poor man's hydrostatic.

I've never had any problems with it. Every year I lube the bearing that the variable pulley spins on.

jinman · Jul 7, 2009

There are many thousands of mowers out there with that variable speed pulley. As the belt becomes worn, you may find it will not work well in some speed settings and may have problems pulling uphill, especially when the pulley gets warm. I believe you will find it slips in the lower gear ranges where the belt runs the farthest out on the pulley. Sometimes the pulley may stick if the mower sets for a long period without use. I've also had to put my toe under the clutch/brake pedal and pull it back to get it to engage. Since the clutch/brake works in tandem, you need to adjust the brakes so they only engage when the pedal is fully depressed (pretty easy to do).

I'm not completely sure, but I believe the deck belt also engages as you lower it with the PTO lever for cutting. When the mechanical PTO belt becomes worn, it may slip, causing the cutting blades to stop when in the higher cutting positions. Normally, cutting at anything but the highest 1 or 2 positions will work fine with little or no belt slip.

Stimw · Jul 9, 2009

I've got a MTD 12.5hp 38 inch cut that has the varriable speed pulley system. I bought it new in 1992 and it still runs great. i have replaced the spindle bearings once. I call it my "Baby Bushhog"! When I bought my property 10 years ago the grass was 2' tall. I cleared over one acre with it. I made a cut then came back and did half cuts.I got my PU (with posi rearend) stuck in slippery mud at the back of my property with my 12' trailer. I dropped the trailer and got the PU unstuck. I took the Baby Bushhog and pulled the trailer right out with no problems.
For mowing it works great. When you come to a tree or flower bed you push the brake peddle part way down and the tractor slows. Once you get out in the open again you just let off the peddle and it speeds right back up very smoothly.

Egon · Jul 9, 2009

In the distant past there were some self propelled swather's with that set up. Two levers for steering and a Wisconsin v4 engine.

Donman · Jul 30, 2009

Well it didn't take long to figure out why the previous owner wanted rid of this tractor. The variable transmission did not work too well. First I noticed scraping noises and then I noticed very little change in ground speed after shifting gears. When I took things apart I found the needle bearings gone in the sheave pulley which caused the pulley to wear grooves in the mounting plate and the shaft. The whole thing just wobbled on the shaft. I went online and found and ordered the parts needed to rebuild the unit (about $80 worth) and rebuilt the pulley setup. I downloaded an owners manual for this tractor and tried following the instructions for adjusting the linkage to the variable pulley but things just didn't seem quite right. I tried mowing with it after adjusting it the best I could but I had major slipping going on so I thought it probably was time for new belts. That is when I found that the front belt that came with the machine was the wrong size. 5 inches wrong! The front and rear belts were both the same size - 53", but the front belt is supposed to be 48". $30 later and two new belts fixed this tractor to the pulling brute that it is now. What a difference! Now I see this "cheap" transmission as an ingenious way to market a low cost transmission that really works good.