Why can't Craftsman use models that mean something? Is there some nomenclature used to translate the 917 number to a model number, i.e. all GT5000's end with ###, etc.?

metal, it might be that somewhere in Sears' past they hired an ex-librarian to designate model numbers. She decided to put them on the Dewey decimal system after getting drunk one night. Does that shed some light?

Metal & Mownie,thanks for the comments.
The tractor has the standard two-blade 42 inch deck.
The model number cited is from the owner's manual.
I don't know how to better describe the unit. My manual
does not indicate the maker of the hydro static trans.

If anyone can be of assistance regarding my question,
your help will be sincerely appreciated.
Donboy

http://www.odref.com/pdf/Hydrogear/150071.pdf

I threw the model number into sears parts and found a picture
of the drive showing retainer spring, part number 4497H for $2.16 for a two-pack. I'll bet you could find these aftermarket under part STD624003. Btw, 917. xxx means that the machine was mfg. by AYP in Swainsboro, GA. Remove the right rear tire and you will have access to this area.

bushleague
I appreciate your reply!
I already have the replacement spring. Need to
know how to best access the area. My unit has
a u-shaped channel frame which covers the right
side of the hydro trans. Unless I overlooked an
access panel, which I doubt, the only way to it
is from the rear or bottom. It appears the room
to manipulate is very tight either way. Which
is better, rear or bottom?
I do not have the mower available to view at this time;
thus the comment regarding the access panel
Thanks! Donboy

busleague and others;
The part # on my Sears packing slip is 123782X, it's described as a torsion spring.
I was able to install it from beneath after dropping the deck. I initially intended to remove the lever and slide the spring over it from the bottom. I was unable to slide the lever out of the clevis due to inadequate size of the frame slot through which the lever protrudes.
Ultimately, I determined that the hand grip on the lever is removable and not molded on as I had assumed from it,s appearance. Is threads on. Once removed I was able to slide the spring over from the top. With soom help I was able to anchor one end of the spring to the clevis and and the other to frame. This part is not a one man procedure!
I threaded on the handle and was done.
I'm still perplexed as how to replace the hydro control lever. It seems to me it can only be done by dropping the entire axle and hydro unit. There should be another approach! However, it took me much wasted time before I determined that the handle threaded onto control lever.
Now I'm a happy camper until the hydro control lever needs to be replaced, which I hope is never!
Thanks for the help! Donboy