InertiaFaze

GMC Sierra Crew Cab 6.5’ box 2WD 2.7T 8Spd

My latest 2.7T fuel economy numbers..... 400 mile AVG 29.1 mpg life of vehicle (11111.1 miles) 22.7 mpg

If 'A' produces 'C' and 'B' produces 'C' then the difference between 'A' and 'B' must always be negligible..............me thinks not.

You've had a lot of great feedback to your post, but how about a simple test? Trade truckswith your brother for 1 tank or 1 week or 500 miles, enough normal driving to determine if it's the truck or the driver. A Red X study? In a Red X study you swap things between a BOB and a WOW and look for differences in the results. If you were to swap with your brother you'd be swapping not only drivers, but locations/routes, payload(?), and maybe fuel sources. A few more ideas. Combined with ideas in previous posts Swap Drivers, etc Keep an eye on steady state V8 FE @ 40/50/60/70 mph and compare with brother or others on GMT.com Keep an eye on AFM/V4 operation. Any noticeable difficulty in achieving AFM? Keep an eye on instantaneous FE while coasting. It should read 99 mpg after a short amount of coasting. This is due to DFCO operation (no fuel consumption). This is a big one. Keep an eye on 25/50/400 mile FE average. Do you get poor FE even on a 25 mile trip with mostly 55 mph cruising? Any Remote start idle time? Tire pressures ok? Excess weight in vehicle? Tools, etc? Try premium (even if winter fuel) Check oil level, oil type? Check air filter Check average speed to see if low (more idle time/low speed-city driving than others) Any 4WD/Auto 4WD usage? Verify DIC Calculation by calculating manually

These transmissions are filled at the transmission assembly plant and normally need no addition/reduction of fluid. On occassion I'm sure it's possible that the vehicle assembly plant might have a need to add/reduce fluid, but as a rule this should be uncommon. Your dealership talked about an "air bubble", there is no "air bubble". If the trans was overfilled it's possible it could create a foaming condition or if underfilled it could cause the lack of suction of fluid but both of those conditions should be extremely rare or non-existent if the oil level is set correctly. Since they removed fluid, a practice that should rarely be required, perhaps you should have them or another dealer recheck the oil level and then adjust it as necessary. It's unlikely, but possible that they removed too much and not that is further adding to you harsh shift concerns.

From the owner's manual Kickdown Mode The accelerator pedal provides an additional downshift after pressing through the kickdown feature. It requires extra pedal pressure near the end of its travel to engage.

Not more pressure.........more area..........same pressure x more area = more force

@The Zip. Point Taken. Read the entire post. Joining the post late, just trying to get caught up. Common theme, 35-50 MPH, AFM Active, no tie to wheel-base length, no tie to brand. @Anon2015 makes some great suggestions in post #155 on page 11. In addition, how about moving the shift lever to M and tapping as necessary to M5? M5 will limit the gear to 5th gear, but it will also inhibit V4 ("AFM"). In doing so it will allow operation at different vehicle speed / engine speed points without V4 activation. Is the noise still present? Have any of the service folks suggested or tried this? I'm guessing they have, but I didn't recall seeing it in any previous posts. Just trying to help.

Sorry for not reading all 14 pages, but has this condition been observed in both short and long wheelbase SUVs? Chevy's, GMC's, Cadillac's? 5.3L-6 Speeds, 6.2L-6 Speeds, 6.2L-8 Speeds? 3.08's, 3.42's, 3.23's Axle ratio? And what are the driving conditions when it occurs? AFM/V4 Active? Engine Speed? Vehicle Speed? Light acceleration, constant speed, coasting, braking? Thanks.

The RWD 6 Spd in LD and HD trucks (not the Allison in the Diesels) was developed exclusively by GM and is not used by any other manufacturers.

As announced, look for a mid-2015 introduction of the 8 Spd and it will be paired with 6.2L engine only. This was not a joint venture with any other manufacturer.