Say I'm at a stop light, I let off the brake and idle off the line I feel a bump. It has been doing this alot lately. Where its becoming very noticible. What is it? The tranny is shifting fine. Even if I give it alittle gas istead of idle off the line it still does it.

 

Back in the day when I had my Hypertech, mine would do this too.
Its like it wouldn't always shift back into first gear when coming to a stop.
Then, when I would barely touch the gas, it would shift to first from second and cause a big bump from the drivetrain.

Sometimes it would do it before I even hit the gas when the light turned green. I would just be sitting there and it would just, thump, shift into first from second, even though I was already stopped at the red light.....weird.

 

Did it just stop one day? What did you do to fix it?

 

Well since you got an 04 call the dealer as it should be under warranty. It's going to be tough to diagnose a problem with typed words...

 

Do you think they will noticed that the pcm is re-programed?

 

Your tune from Allen should have the newest reflash from GM so there should be no reason for them to mess with your PCM.

Is it like a shudder you are experiencing?

 

I sold it....but not for that reason.

It didn't do it all the time....just every once in a while.
I have no clue....it was a '99 Sierra

 

Its just like bmbutler explained it. It's just a bump as soon as I let off the brake. I think butler is right. I just need to take it to the dealer when I get back to WA. and see what they say

 

I had this very same problem, took it to the dealer and found a burnt band from 2-4 accumulator and rod hanging up on the case. They ended up rebuilding the tranny under warranty. I also had the HTPP3 and they did ask if i had reprogrammed the pcm, but i removed the program before i took it down there!

 

Mine only did it after the programmer as well.......hmmmmm?