Here are the instructions, straight out of a pirated copy of the "Shopsmith Authorized Service Manual":
Replacing The Speed Changer
3/32" Allen wrench
10 weight non-detergent oil
Medium - flat screw driver
Medium - Phillips screw driver
1. Turn off an unplug the Mark V.
2. Attach the sanding disk to the main spindle and rotate it away from you as you turn the control handle to fast. DO NOT force. This will take the tension off of the motor drive belt so that you can remove it from the motor pulley.
3. Remove the belt cover and secure out of your way to your left with tape or string. Slide the headstock and carriage to the right (towards the base mount) as far as they win go. Secure the headstock and carriage locks.
4. Remove the drive belt from the motor pulley by genuy sliding off one side of the belt and rotating the motor shaft so that belt will ride off entirely.
5. Remove the nameplate assembly to expose the access hole located on opposite of the control handle. NOTE: depending on the age of your unit this can be done by popping off with a flat head screw driver or by removing the screw located at the bottom of the nameplate cover. Some older units did not have access holes and you may have to lower the motor pan assembly down on the bench tubes to have enough room to work on unit
6. Depress the leaf spring on the back of quadrant and swing the retaining loop out of the way.
7. Use 3/32" Allen wrench to remove the control handle.
8. Remove the 3 large screws which are now exposed The entire mechanism can now be removed from the casting for cleaning and replacement. NOTE: Pay close attention to the position of the small spring (504196) when removing the speed dial.
1. Install the small spring (504196) to its original position and, put on the speed dial.
2. Push the speed control bracket into the opening in the headstock, line up the 3 screw holes and secure.
3. Turn the speed dial by hand until the "Fast" setting is aligned with the marker on the casting of headstock.
4. Spread sheaves on the motor shaft and reattach belt.
5. Depress the leaf spring on quadrant and reattach the retaining loop.
6. Replace the control handle and tighten the set screw on the worm control shaft indentation. Replace the belt cover and name plate assembly.
7. Prior to start up you must put the unit at a "slow speed". Put the 12" sanding disk on main spindle. Turn the disk toward you and the speed control down to slow at the same DO NOT force.
8. Perform a high speed adjustment.
You might also want to look at the photos in Thread #144. (http://www.shopsmith.net/forums/showthread.htm?t=144
With all good wishes,