To make a long story short- I'd been hunting for a TC hunting between lockup and open problem for quite some time now, and had also noticed a slightly lopey running engine under light load.
I thought that the different sound came from the smarty (thinking about timing)
I had messed around with various capacitors etc, and had the TC acting quite right.

Well today I started a little project I had put off a long time- change the alternator brushes- I thought this won't be necessary since the alternator tested good on a load test.
I found that the front brush was almost gone and there had been a lot of arcing going on.

Plug in the new little bugger /(got it from Fostertruck) slap alternator back together (Took me a 3/8" ratchet with 7mm, 8mm, 10mm 12mm sockets and a 13mm open ended wrench for the battery neg. terminal and a stubby phillips screwdriver. Took about 30 minutes with the alternator on the truck.

Started the engine and well- idle is quieter- I high idled it and there's definitely a difference. Took it for a spin. Very nice lockup engagement, rock solid, no more hunting and more consistent shift points. I removed the capacitor and took a very small one to get rid of the problem that my TC woudn't unlock until I really mashed it. Still very solid lockup, but no more delay when trying to pass someone.

Had to bring my wife to the inlaws today, the first thing she noticed was that the truck ran much smoother.

Since I'm a methodical guy I reinstalled the old brushes and the problems with the TC were back- and the rough running too. So I took the OBD2 laptop and let it graph the throttle percentage over time- this looked like a mix between a sine wave and saw teeth from the ECM and like some passenger trying to write while the driver intends to win the Baja California from the PCM.
Swapped the brushes again and redid the graphing- voila-straight lines. (as long as I didn't move the pedal)

So now I assume that the bad brushes did fire enough to somehow make the PCM freak out completely and at least "wiggle the go pedal a good bit" for the ECM- and since the smarty is there to improve throttle response the ECM tried to follow the signal as quick as possible.- Result some weird lope under light loads.
While driving now I did also see lower EGTs on the same mountain at the same speed as usual. (Roughly 50-75F lower)

So I think that if you hunt for lockup problems you could take a shot after those brushes after cleaning all the grounds and connectors. They are quite cheap and no PIA to swap.

Sorry for being that long winded,

AlpineRAM

 

I think I read that close, but how many miles on the truck when you did this? wondering if its a 40, 50, 100 k mile thing?

 

I've got approx 185 k miles. But I think that the problems started (in a lighter form) somewhere around the 100 k miles mark.