Over the course of this summer, our mower has been losing drive power. At first it would fail to climb hills that it handled easily when new. I was hoping to nurse it through the summer and fix it this winter, but now it will not move under its own power. The brake is not engaged, and the freewheel control is in the ''engaged'' position as it should be. The engine is fine, with plenty of power for cutting grass. New motion drive belt did not help. I've tried purging the transmission per the owner's manual instructions, but to no avail. I'm figuring that the hydrostatic drive unit will need to be repaired or replaced, but the owner's manual gives no data on this process and no data on what make and model the transmission is.
Any recommendations on my best course of action? I'd prefer to fix it myself and have 30 years of extensive experience fixing cars, motorcycles, mowers, etc. However I've never been inside a hydrostatic transmission and don't know what to expect if I open it up.
It sounds like the oil in transaxle is degraded.The transaxle is supposed to be a sealed unit requiring no service but over time the oil will get dirty enough to cause problems like you are describing.Remove the back hitch plate and look at the transaxle it will have a rubber vent hose or a 1/4 Allen wrench fitting on top. You will need to purchase a battery suction bulb from sears automotive and use it to remove as much oil from transaxle as possible. Warm the transaxle up first by running it around,then suction the oil out.Refill with a good synthetic motor oil 15w-50 or 20w-50 like Amsoil or Mobil 1.Do not use transmission fluid or hydraulic fluid. When adding the new oil back fill it to within 1.5 in from the top,be sure to allow this amount of air space in top of transaxle for expansion.
Testimonial: "This procedure was worth trying, but did not solve my problem. I suspect that there is some other reason my transmission does not drive the wheels."
You are wasting your time fooling with changing the oil in the transaxle. By the time they quit running the damage is pretty much done. It may last another seven years. It may last another seven minutes. It may do absolutely nothing at all. Why waste the time? If you are going to go to all that trouble I'd drop the old transaxle out and install a new one. If it is a K46 Tuff Torq like a lot of Sears tractors, new ones in factory sealed boxes are listed on the internet and on Ebay for as low as $225 with free shipping. Sometimes you can even get them cheaper by bidding.
Remove the mower deck. Jack up the tractor with a pump jack under the rear frame and set two jack stands under the frame right ahead of the rear wheels. Remove the rear wheels being careful to retain the 2" locking keys in the axle grooves and reinstall them in the axle when reassembling. Strongly suggest your start taking digital "before and after photos" at this point if you haven't done this before so you have a reference when reinstall time rolls around.
Getting yourself an exploded parts view of the rear end of the tractor will help immensely. Should be one in your tractor manuals. Take the drive belt off the transaxle. Remove the shift linkage. Remove the brake and the emergency brake rods from the transaxle. Remove the mounting strap bolts. Then there are four bolts that hold the transaxle to the frame. Put your jack underneath the transaxle (barely or no pressure!) and get someone to hold it steady while you back out the four remaining bolts. Transaxle will drop onto jack and then you can lower it down and replace it with the new one doing all steps in reverse. It ain't rocket science, more of just a royal PITA. I strongly suggest you replace the drive belt while you got everything apart as that is the last thing you will want to be doing if it breaks a few days later. Thread it around the drive pulley and the tension pulleys in the middle and get it so all set up so all you have to do is slip it over the transaxle pulley and push it around the three center pulley keepers when the new transaxle is in. Voila, it's a tractor again Bob.
NOW, if that wasn't enough of a waste of a beautiful fall afternoon, you can go and drain the oil from the old K46 and replace it with 2.30 liters of 5W/50 Mobil 1 synthetic...NOT transmission fluid. Then if the new K46 self destructs in a couple years (as they are prone to do), you can take it out and see if it would have worked in the first place. If you didn't fix it by changing the oil and you are a masochist, there are rebuild kits for $165 or you can just get another K46 for $225 on Ebay.
Buena suerte Juan...
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Heads up. he is right but you need to open the transmission to remove the metal filter screen on the bottom of the hydro pump. it gets full of gunk and will not allow oil to filter thru. i suggest you open it carefully, photograph the order in which parts fit together. Then remove the filter. You will want to drill and tap a hole as close to the bottom of the transmission as possible and put in a plug or drain ****. the filter for this transmission is 96.00 from sears parts direct.com. so if you put a drain valve in, you should just changed your oil frequently to rid of dirt and metal shavings.
Check the neutral control if yours has it - and also make sure every single control is clear of grass and that it is all the way into gear - clean all the underneath parts and check the operation again.
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