OK has anyone had any luck figuring out what causes the overdrive to slip under load (going up a hill, pullin trailer, driving with a load in the bed). I have a 96 K1500 5.7 liter Z71. It happens when I have the truck on cruise and start to go over an overpass, the cruise control slowly accels to keep the truck at the set speed (70mph) and then the (what I think) transmission slips for a split second and the tranny then downshifts to third to speed up. There is no change in rpms during the slip (or misfire) there is no check engine light coming on. I just had the tranny rebuilt 3 days ago because of this slip and nothing has changed. Parts that have been replaced in the last two years include plugs, wires, distributor, fuel pressure regulator, fuel pump (twice), lower and upper intake manifold gaskets. Also at idle there is a slight misfire but no check engine light. Does anyone know the cure to this problem.

Is the trans slipping or is it a stumble or misfire just before the maximum load/downshift?

You know the more I think about it, I'm almost positive that it is a misfire. It does miss just before max load (in my case in OD cruising over an overpass). It will also miss when sitting at a red light in gear. At a red light the miss does not always occur though. There is no constant time interval between the misses at the red light.

Any ideas on a remedy?

It sounds like I had the same problem (except the missing at a light, but my idle is really low) with my '96 5.7 liter. I replaced the fuel filter, had the fuel pressure checked, put BG fuel system cleaner through it, looked for codes and maybe a couple other things. It turned out to be a cracked spark plug and corroded distributor. The plugs weren't that old either, but the distributor was probably so corroded because I live in a very wet environment. So check the plugs closely (inside and outside porcelain), and distibutor. Hope it helps.

Thanks for the advice. I'll give an update after Ive checked in to the plugs etc.

Check Distributor Pickup Coil 12 Bucks An About 3hrs. It Worked 4 Me