When I had my C4 rebuilt for my '74 I think they put extra clutch discs in and a TransGo kit. It is almost impossible to accelerate from a stop without churping the tires on the 1 to 2 shift.
I'm with Paul on this one. The 40-2 is what I've used in the past (when I actually bought a kit instead of making my own) and it was always a great investment. Made a sluggish shifting C4 shift like a race C4. Of course, if the rest of the trans is worn out, it's not going to improve a thing other than lighten your wallet a little bit. Also using a Z servo or something small like that, you're not going to notice as much of a difference as you would if you have an A, B, C, H, R servo. Lately we've built our own shift kits for cheap. Not that hard to do if you study the valve body and oil flow, and the BEST shifting C4 I ever "did up" was the one in my old '74 Maverick turbo. It was also a home made shift kit, complete with R servo, increased line pressure (175 psi) and a fresh rebuild. Even with all that torque and a fairly loose (compared to a stocker) converter it would smoke the tires if I was on the throttle & shifted into 2nd or even into 3rd gear. Care had to be excercised to keep it from getting out of shape...engine had too much power for street driving and the trans shifted too hard for the DOT Futura back tires. Of course I let Old Guy do the C4s now...it's been a while since I've been through one. I've been doing too many powerglides!
