ive had both trannys i think the 68l0e is stronger then the 46l0e and better mpg

 

Yeah,
the 6 speed is definitely the stronger of the two transmissions,
acceleration is also a little better with the 6 speed.
I prefer the 4 speed because it is smoother than the 6 speed, though.

If you are going to do a lot of heavy towing than the 6 speed would be the best choice,
otherwise there is nothing wrong with the 4 speed.

Joe

 

I own an '08 Sierra with the 4 speed and had a '14 Silverado 6 speed as a loaner for a week. I definitely prefer the 6 speed. It shifted smoothly and felt like it always knew which gear to be in. The 4 speed is still good, but I prefer the extra gears.

 

Let's say I get a 4 speed and decide I want a 6 speed, is it possible to swap one in?

 

Technically, yes. However would you really be willing to spend that much to swap out the transmission down the road? IMO, I'd get the 6 speed from the get-go. You won't be disappointed and it should save you some money and a headache. If I were to buy again, I wouldn't think twice about getting the 6 speed over the 4 speed.

 

My 03 Tahoe was 4 speed my 11 sierra cc is six speed. Personally I like the 4 speed better, not hunting gears as much. However I have a tune and had Lew change my shift points on the 1-2 shifts.

 

Good point... am I right that they started with the 6 speeds in 09 crew cab 5.3s?

 

The '07 Denalis had the 6 speed. 2009 was the first year on the 5.3/6.2's.

 

After I tuned the truck, my 6 speed shifts better. I have no complaints with it. It doesn't hunt nearly as much now that the engine is putting out more power.

 

I hated my 6 speed when I had Active Fuel Management (AFM) running. The transmission does tend to put you into a higher gear earlier to save fuel, at the same time the AFM shuts down 4 cylinders in the engine. I found it very annoying, it seemed like it took way too long for the transmission to downshift and to return to 8 cylinders firing.

I got the device to plug into the OBDII port that disables the AFM, not I'm very happy with the performance of the 5.3 coupled with the 6 speed tranny.

I also have a 6 speed tranny in my Acadia, and have had no problems with it. During rough slippery weather sometimes I put the tranny (Sierra and Acadia) into manual and select 4th gear (therefore allowing shifts from 1st through 4th gears) to lock out 5th and 6th so that I have instant power available when I need to spin some wheels to make it around a slippery corner, or to shift down to 2nd or 3rd quickly to slow the vehicle down on a slippery decline / corner without touching the dreaded brake pedal.