so i may have or may have not jumped the gun on the decision for a new tranny so let me know what you think. i have a 03 auto with about 65k on it and it recently started acting up. when warmed up it wont shift from first to second gear when leaving a light but after i get it into second it shifts fine through the rest of the gears. its also fine when the truck is cold. no codes are showing except a p0633 which i believe is from my bullydog.
any input would help, thanks

 

also forgot to mention, when warmed up it makes a knocking noise upon deceleration. changed the fluid the other day and it was black, the magnet was packed but the fluid itself did not smell burnt although when i drive the truck for a long period of time it smells like burnt clutch,
thanks agains guys

 

Sounds like the front band needs to be adjusted. If it adjusts all the way out with no improvement... then it needs replacing

 

I'm no tranny guru, but I have adjusted my bands a couple of times. Not too difficult and won't cost you anything (except fluid, filter and an in-lb torque wrench).

You may also want to replace the governor pressure solenoid, I think they're $75 or so. It may help but don't shoot me if it doesn't.

 

Black fluid and a packed magnet? Yeah it is terminal. Brown fluid is usually not a good sign, but black with metal shavings is a sign of serious damage.