2000 Chevrolet Malibu - Transmission or Computer?

[Eleventeen]

I have a 2000 Chevrolet Malibu (LS, v6, AT) that has been having some trouble lately. When the car is attempting to shift between 3rd and 4th gear, either up or down, the transmission feels like it slips (the RPMs jump up and down, too.) This only happens when I am accelerating moderately or quickly, usually going up hill; when I do it carefully, it shifts smoothly. This part sounds mechanical to me.

But here is the odd part. If you allow it to slip for about 15+ seconds, the engine shuts down. After that, it won't start again until you reset the computer (unplug the negative battery cable.) All of the electronics work fine before I reset it, and the engine cranks just fine. It just seems as though no fuel gets to the engine.

Anyone have any ideas what could be wrong? Does this seem mechanical, electric, or both?
Before I figured out that resetting the computer worked, I changed the fuel pump. No change. The check engine light is not on, and doesn't go on even when I don't reset it. Thanks for the suggestions so far. Gives me a few ideas.
160,000 miles. Problem started 15,000 miles ago. Also note I am not a big Chevy fan to begin with.

 

[toolman]

you might want to check your fuel pump cause it can cause a real bad hesitation. but if your check engine light is on you should be able to take it to autozone and have them scan it for free and it might be a shift solenoid that went bad

 

[ky509]

It sounds like a transmission problem that is effecting the computer. You may be losing the clutches in your tranny. If it has a lot of miles, 100k plus, then I would bet the transmission in need of a rebuild. In any case a simple hook up on an analyzer will help to pin point your problem