Which Gear for SC "Foothills"?

[Jerome Nelson]

Howdy!

I've just moved from very flat, Central Florida — to hilly, Greenville area, South Carolina.

I had the automatic transmission rebuilt (twice) and upgraded the transmission radiator/cooler.

I remember my Florida, transmission mechanic saying something about keeping the Tahoe in 3rd gear (instead of "D"), for our trip to mountainous, North East Tennessee. However, I'm not sure which is appropriate for our moderate, hilly region in Upstate Carolina. (To be clear, I'm not towing or hauling anything. Just a daily driver with kids.) Thoughts?

Also, when we do take a trip to the mountains (1 hour away), should we be in 3rd gear?

Vehicle Details:
2000 TWD 5.3 Tahoe
205K Miles
Automatic Transmission: 4L60E 4-X Speed

 

[Marky Dissod]

You'l never get 18MpG uphill. If the hills are steep or long enough, your axle gear is 3.73 or less,
and your 4L60E is 'indecisive' between 3rd & 4th (or worse - between 3rd & 2nd!),
it may be very helpful to put the shifter in '3' to avoid 4th when going uphill.

(If you somehow got lucky and your axle gear is 4.10, nevermind what your mech said about using 3rd to avoid 4th.)

That said, if you're NOT towing / hauling, it'd be better for the 4L60E in the long run to have the pcm tuned to be less 'shifty'.
If your axle gear is 3.42 or less, using Tow / Haul mode may not be helpful enough.