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Troubleshooting Craftsman Mower Front Wheel Drive Problems

Self Propelled...Not

So the motor on your self propelled, single speed front wheel drive Craftsman mower runs great, but lately you have noticed the wheels slipping and that you now have to push the mower across the lawn. You might even be getting hot, tired, and just a bit frustrated. Fortunately, there is no need to trade the old beast in just yet for an outrageously expensive yuppie mower when all your machine needs is a little TLC.

To use this tutorial, refer to the diagrams and parts lists found in your Owner's Manual. If you do not have a manual, you can go online to sears.com, navigate to the parts area, enter your model number, locate the diagram and parts list, and save / print for later use.

A typical diagram looks something like this:

Mower's front end - exploded view.


Safety -- Must Read !!!

Before we procede, let's talk about safety. Just like Norm says on The New Yankee Workshop, read and understand the owners manual for your mower. Always wear safety glasses. And, above all, never put your fingers, hands, feet, or any other body parts anywhere near moving blades, belts, or pulleys when the machine is running.

Those body parts may not be important to you, but cleaning up the mess made from losing them is very unappetizing !!!



Localizing the Trouble

The problem has already been defined: the front wheels don't pull the mower like they did when you first bought the machine. Obviously, if the tread is worn off the wheels, performance will suffer. Since this is a lawn mower and not a race car, slick wheels should be replaced. Also, the gear teeth on the wheels and the pinions should be checked. Block the mower up and remove the wheels, taking care not to lose any spring clips or nuts. Inspect the gear teeth on the wheels and replace if teeth are missing or mangled. While the wheels are off, try spinning the pinions by hand. Should either pinion spin freely on the drive shaft, the keying mechanism -- whether an actual key or flats milled on the shaft -- is damaged and the shaft or transmission assembly will need replacing. If the drive continues to perform poorly after replacing worn/damaged wheels, or if there was no evident problem with either the pinions or the wheels, further checks are required to determine the source of the trouble.

Begin with an inspection of the readily accessable parts. With the motor NOT running, remove the drive cover. Is the belt there? Does it feel tight? Does everything seem to be connected properly? Obviously, if the belt, cable, or springs are loose or damaged, they should be repaired. Belt replacement procedures are explained in the Owners Manual.

If everything appears ok, perform a VISUAL inspection of the same area with the motor running. Start the motor in the normal fashion and verify that the belt does actually move. If it does not, there is a chance the key driving the engine pulley is sheared, though I have never seen such a thing happen, even on my own customized, full race, overclocked machines.

Next, check the drive control cable. With the motor still running, lift the front wheels slightly off the ground and engage the drive control lever while watching the end of the cable. Again, this is a visual inspection -- remember the SAFETY discussion above. The cable should move the shifter arm coming out of the top of the gear case to where it almost touches (or lightly touches) the worm shaft upon which drive pulley is mounted. The front wheels should try to turn, but may not, depending on the extent of your particular problem. If the cable does not seem to be engaging properly, there is a chance it has stretched and requires replacing. Though the control cable is rarely the problem, the simple check ensures that time is not wasted on more complex procedures. Shut down the engine and take a moment to....

Review

At this point, you know the:
  • Wheels were repaired/replaced if the tread or gear teeth showed excessive wear.
  • Pinions are driving the wheels properly.
  • Belt is in good condition.
  • Miscellaneous springs, nuts, bolts and fasteners are present and working.
  • Drive control cable funtions properly.
  • Engine pulley / key intact.

If all this is correct, the problem lies within the Gear Case Assembly and you should order the newest, upgraded transaxle from me immediately **. In the older style assembly, #702511, the usual suspect is the worm / helical gear engagement -- which has worn to the point the pieces are making intermittent or casual contact. The amount of engagement might be sufficient to make the wheels turn, but not enough to transmit any actual power to the wheels to pull the mower. In more extreme cases, a portion of the gear or worm can be so worn that the drive system seems to periodically "bind". Proceed by removing the transaxle from the frame using the instructions below so that repairs can be made at a workbench.

Transaxle Removal Instructions


Tools Required:
  • Flat head screwdriver
  • Long nose pliers
  • Regular pliers
  • Slip joint pliers (Channel Locks) or pipe wrench
  • 1/4" or 3/8" drive 7/16" socket and a short extension
  • 7/16" combination wrench

Removing and replacing the transmission can be a bit tricky, but can usually be done in an hour or two. The following steps are applicable to most single speed Craftsman front wheel drive mowers:

  1. Lift the mower onto saw horses or a Work Mate, positioning the machine such that the weight is supported by the frame, not the wheels, and in such a way that allows complete access to the front end. The work can be done on the floor with the front end raised, but the other method is far more comfortable.

  2. Check for stability. Make sure the mower is not going to fall on your feet, causing unwanted pain and embarrassment.

  3.Remove the Drive Cover (if it is not already off).

  4. Remove the Belt from the Drive Pulley per owner's manual. The belt does not have to come all the way off, but care must be taken later during reassembly to ensure the belt is located properly on the Engine Pulley (the belt guard under the motor limits visibility, so a flashlight might be needed to ensure belt is seated in the "Vee").

  5. Remove both Wheels, Pinions, and Dust Covers, noting the location of any Felt Washers and/or spacer Washers.

  6. Unscrew the 3 bolts that hold the Engagement Bracket and the Spring Bracket to the Gear Case and unhook the Spring from the Shifter.

  7. Pull the Engagement Bracket off the Spring Retainer.

  8. Unhook the Drive Control Cable from the Shifter (there is no need to unclamp the cable from the bracket).

  9. Remove the Wheel Adjuster Assembly located on the left side of the machine as you face the front by unscrewing the two 1/4-20 hex nuts (7/16" hex) located on the inside of the frame. NOTE: on this step there are differing opinions. Some say both adjuster assemblies need to be removed. It does make the job easier if both are off, but the right side adjuster has less clearance for a wrench, and is a bit of a pain to remove / replace.

  10. Slide the Driveshaft Cover off the Driveshaft.

  11. Still facing the front of the machine, grasp the transmission firmly and move it to your left. At this point it is free of any restraints. Continue holding the transmission and orient so that the pulley clears the hole in the frame. Move to the bench for final disassembly

  12. Clamp the lower housing firmly in a bench vise. Remove the 3/8-16 Hex Flange Nut (9/16" hex) from the Worm Shaft. Some have reported problems breaking the nut loose. An alternative: finish opening the aluminum housing by removing the final bolt. Tap the housing and pull apart. The halves should separate fairly easily. By clamping the worm real tight in a bench vise or with vise grips, the nut should be able to be loosened.

Hopefully, you have already ordered your replacement transmission from us and are ready to reassemble. Since the new one is a far simpler design, reversing the order above will work -- skipping the steps for the bracket pieces, which are no longer needed.

** If you take advantage of the fact that I provide the entire diagnostic procedures as well as detailed instructions here on this site, buying the replacement from me is the logical conclusion. Sure, my price might be a dollar or two more (don't forget "shipping and handling" is always included in my price), but should you run into a snag and need some help... you can always email me and I WILL try to help. Try that with the other parts distributtors.

[A work in progress...]

Updated on 2007-09-18 03:31:48 by yardman  Printable Version
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