Ok I've been battling this issue for a long time. I have a Silverado 1/2 ton with a swapped in 80E, vacuum modulated.

I want my WOT shift points to all be right about 5700 RPM. To make the tranny shift there on a WOT run from a stop I set all of the WOT shift tables at 5000 RPM. I have the 1-2 WOT shift set at 55 mph, 2-3 at 88 mph, and 3-4 at 256 (not that it matters).

When running from a dead stop through the gears, it shifts correctly right around 5700. However, if I go WOT when I'm already rolling at something like 50-60 mph, it will drop down a gear or two and start pulling from something like 5000-5300. In these cases, it will run to almost 6500 RPM before the shift.

I have heard from several different people that are having WOT shift point issues with their 80E trannies. Does anyone have a solution to this? I tried zeroing out the WOT shift speeds but then the trans goes 2-1-2-1 when I go WOT from a cruising speed of around 40 mph. I'm out of ideas.