the sledgehammer was introduced in 1989 and was traxxas's first venture into the true monster truck class. there are 3 versions of the truck - white plastic with gold skids ('89-'92), white chassis with black skids ('93-'94), and black chassis with blue skids ('95-'02) - to the best of my knowledge the truck was discontinued in '02 but '04 sticks in my head as well. many parts are still available for the truck in the black plastic versions. bodies and decal sheets have become very hard to come by within the last 2 years, so if you have a clear body, use it wisely.
some mods that i use on my sledges to bring them up to today's spec is to only run 4 shocks (much smoother ride) and to swap the stock differential for a nitro stampede differential. this moves the output yokes outside the tranny case so you don't have to tear the truck apart to change the drive yoke. other than that, full bearings, 4 shocks and a decent balanced set of tires will make the truck come alive as well as a torquey motor (mag mayhems run great in this truck).
all in all, a fun truck and i'll probably always hold onto mine because i restored it to almost original form and it runs great for me.