I have been told by some people that you should never hammer down hard while in overdrive,you should always drop down to drive. I am not sure if this means at the drag strip only or when you do a roll on at crusing speeds(40-80mph) or what. Is this a true thing or just another myth? What do you think?

 

There are many opinion on this.
One set of opinions says that the benefit of the overrun clutches engaged in manual third adds holding power by assisting the sprag. I say that holding the overrun clutches robs line pressure from the pack that needs pressure the most: the 3-4 clutch pack.
Also, a 3-2 downshift is the most complex downshift a 4L60-E has to do. It has to disengage the 3-4 pack while engaging the band at the same time. It's complex enough to time it right that there is even a dedicated solenoid for doing just exactly this. A 4-2 downshift is actually easier on it because the band is already engaged.

There is no need to drop to drive to nail the throttle. That would waste time in my opinion. It's not saving anything. The weakest pack in a 4L60-E is the 3-4 pack and that's engaged in third and fourth, so you're going to be on it anyway.

 

Unless he may want to disengage the TCC lockup & downshift faster than the PCM's logic. Until I got ahold of HPT, a WOT transition involved time taken to disengage TCC lockup plus time for logic to accomplish the 4-3 downshift. In stock form, that just felt too sluggish. I even noticed that with the rice I now own... With HPT, that's been resolved for my C10.

 

It's not recommended to kick down on the highway but I still do, it's ok to just leave it in od at the strip.