With autotrac on a truck like ours, bet on about a 30-35% driveline loss... Maybe more... It makes me sick... ?
You will see about 20% loss on like an F-Body Auto Trans... And about 16-18% on a 6 Speed ...
A Z66 will lose about 28-30% through the driveline ...
Redshift, also remember, I am at about 1600 FT here ... Humidity is about 9-14% this time of year ...
Also, the dyno here that I see all the time is a little on the conservative side IMHO ...
The G-Tech is good for measuring "differences" in acceleration vs. mods ... But the key is to understand that you have to "drive the truck the same each time" ... i.e. don't load the converter, don't try for your best 0-60 time, etc.... Unless you are trying to get a "best run" ...
When you make a equipment change or adjustment, then if you have a rock solid way of driving it the same every time, your losses/gains will be a little more accurate...
You'll get the hang of it, and understand eventually what the G Tech likes and don't like ...
11H