As the title states, I'm heading to the dyno tomorrow for the first time in my life. I know that the truck needs to be in 3rd gear which means turning the OD OFF with the button. But question one, what RPM do I need to be at so it doesnt down shift to second and 3rd, what about the fuel curve under than specified RPM??

 

Your dyno guy should be able to handle those ?s for but if not then I will..

80mph in 3rd gear is 3,200 rpms. That should be a good spot to nail it with out it down shifting.

Sal has responded to the A/F ? before. At the track when your L shifts into 3rd gear @ WOT you will never go below 3,000 rpms thus not worring about it. The only time your below 3,000rpms is during the launch and you only there for a sec or so. Understand?

 

That makes perfect sense, but since I use my truck as a daily driver, I SOMETIMES never go above 3000 RPM in my journeys, so Id like to know that everything is fine in that area.

 

If your just worried about crusing conditions...DONT! You not making any boost @ crusing speeds and under part throttle you still making less boost then 8psi witch is well with in factory operating range.
The only time tuning become an issue @ part throttle is when you start to add on BIG items that effect HP/TQ constantly like Heads,Cams,Stoker kits, etc....

Those are very good ?s to ask if you know little about mods vs. tuning on any car/truck.

 

run the truck up to about 65mph and it won't downshift.

good luck. have fun.

later,
chris

 

If the truck down shifts, stop on the pull and start over.

 

Really? Mine down shifts @ 65???

 

Bring it up to 3k in 3rd gear. That you should get you just about 70mph. Hit it from there.

 

Prolly not if you have the overdrive off