this is a word that has a bunch of answers..........so yes i looked and no i cannot find im missing something somewhere

so i have a 97 blazer

idles fine drives fine, every thing is fine, so im going down the road and my blazer when it hits about 3.5k rpm light just dim nothing turns off, but ALL the lights dim anything past 4k the battery light comes on untill it shifts gears, then its fine again

the way i found out about this problem is this winter when i was slipping on the ice and spinning and stuff

but like i was saying battery stays charged, runs above 12v my gauge says 14 or above that when cold...............

 

Because I had a similar problem last year with my '97 (owned since new), I'll suggest 2 things to look at.

The first is the belt tensioner.
I thought I had a bad alternator. My lights would dim intermitantly, at any and all situations, but mostly when idling. Gauge would dip under 12V. Rev the engine, 14V +. I could see the headlights pulsing. Took the alternator out, and into Advance Autoparts (it's a lifetime guaranteed unit). Darn thing tested fine.
About 6 months later, the tensioner broke. It was the original unit.
With your truck idling, open the hood and look at the ternsioner. Is the belt tensioner steady, or jumping around

The second item is the Alternator itself. Because you only see this at high RPMs, it's hard to test it while idling.
I'd suggest you go to AutoZone or AdvanceAuto and have them test it. It's free, and they can test the electrical system while it's in the car/truck. I had advanceAuto test mine while in the truck, but everything tested OK. Just a flukey intermittant tensioner thing.