I've been using the nice weather to fight with involved automotive repair.
I overhauled the transmission in my old truck this winter. First time I've been into an automatic really, in the past I've just rolled the dice on a random one in the junkyard. Cheaper and easier really, but some risk involved. If you pick one from a car that was involved in an accident, you have a pretty good idea that the transmission was working.
Anyway, the overhauled transmission was almost perfect. The only problem was that sometimes I was getting a slip in overdrive. The computer could detect this, and would ramp up the hydraulic pressure to maximum in an effort to really smash the clutch packs together hard. Slippage is very bad for an automatic, and will cause failure in short order.
So it came back apart this week. I think I've found my problem. Wear that I overlooked the first time. This is the forward clutch hub. On these splines ride the friction disks for the direct clutch. The little notches that look almost like they are suppose to be there? Yea, that's wear. I suspect that they are catching the new friction disks and preventing them from fully and evenly engaging with the mating steel plates.
I really hope this is the problem, this is not an easy or fun transmission to pull and reinstall.
Old part:
For comparison, the new part: