Victor,
I'm attaching the pictures of the shift-shaft extension I made for the Kansas City customer. It isn't that difficult to do.
Photo 1 shows the parts I used to make the extension. The piece of square stock and the two short spacers on the right side of the picture are only for aligning and assembling the extension. The 1/4"-28 SAE All-Thread in the center is what will hold the extension to the transaxle shift shaft. The shift arm in the lower-left corner can be any shift arm -- you will be cutting off most of it, only keeping enough to weld the long spacer tube to. The U-shaped piece at the top-left is the original Murray shift yoke.
The long shift shaft is 4-1/4" longer than the standard 820 short shift shaft. With the 1/4" thickness of the shift arm, the long spacer will need to be 3" long (See NOTE 2 below). I used a piece of 7/8" ID by 1-1/8" OD (1/8" wall) mild steel tubing -- it was what I had in my stockpile.
Photo 2 shows the extension parts aligned, ready to weld. Since the key stock has to extend beyond the bottom and top pieces to keep them aligned, the short spacers go around the extended key stock so all three pieces can be clamped with a long C-clamp for welding.
Photo 3 shows the parts welded together. The key-stock piece is critical in keeping the transaxle shift-arm and the Murray shift-yoke squares aligned for proper shifting alignment. Once welded, the key stock can be removed.
And Photo 4 shows the extension installed on a new 5-speed Peerless 820-001B made-for-Murray transaxle. This will also fit the 6-speed 820-040 transaxle, but the 820-040 has a 3/4" input shaft instead of the 5/8" input shaft used on Murrays. Actually, it will fit any 820 with the short shift shaft, if you have another 820 you want to use on your Murray.
NOTE 1: When installing the 1/4" All-Thread into the transaxle shift shaft, the 3/8" square hole in the Murray yoke will allow unacceptable slop at the top, so you'll need a shouldered bushing in the square yoke hole to keep the All-Thread from moving around. I cut off a short piece of a Kohler Flywheel Fan Spacer, P/N 24 112 04-S, from a Kohler Command engine to make this bushing (See next thread in this Post). Unfortunately, this Spacer is obsolete from Kohler, so unless you have a junk Kohler in your boneyard, you'll need to come up with your own spacer. A flat washer, lock washer, and nut will finish the installation; I'd recommend a Nylock nut.
And I use blue Loctite on all the threads for security.
NOTE 2: The 820-037 long-shift-shaft made-for-Murray transaxle also used a tall input shaft that extended the 5/8" pulley-mount section one inch (1.0") above the input-shaft post on the top cover. This was to keep the transaxle pulley aligned with the engine and idler pulleys with the extended mounts for the axle housings and the mower chassis. Using a standard short input shaft 820 on a Murray lawn tractor will work fine, and will allow the 3"-long extension tube to put the shifter exactly where it needs to be. If you are using the 820 on a Murray garden tractor, you will need to use a 4"-long extension tube and the taller input shaft.
Respectfully,
Rodney Rom