I've been working up to get this thing back out and in tip-top shape again. It's spent almost all of it's time for the past 5 years in a garage

Anyway the transmission is slipping going from 2nd to 3rd. This is a C6 transmission and it has adjustable bands. I adjusted the intermediate band according to spec, took a LOT of turns to tighten the adjustment screw but it finally got down there. There was a marked improvement but it still slips.

I'm not a transmission expert, aside from this the most I've done with them is change the fluid&filter. I'm assuming that this means replace or rebuild though. I had some thought of trying to do it myself... not sure if I want to tackle that though. I've got a garage, jacks, a pretty wide assortment of sockets and wrenches, a 1/2" torque wrench that reads ft lbs and a 3/8" that reads inch lbs. What other sorts of tools does one need? Should I just wise up and find a tranny shop instead?