Thanks for the information guys, I am also looking at changing my 275/55R20s to something with a little less overall diameter...maybe 285/50R20s which is about 1" less in diameter or finding something 3" to 4" less diameter.

 

I drove a Yukon Denali with 3.42 gears, 6.2 engine and 6 speed tranny on a 4,000 mile trip and I don't think 3.42 is too much gear. In fact it had a hard time holding 6th gear at around 75-80 mph, the thing just bogs down and I had to drive in 5th gear at those speeds.

I think you would benefit from 3.73 gears.

 

I have a 6spd with 3.42s and he is right 3.73 probably would be PERFECT 4.10s may be a little much since the first gears a 4

 

3,42 best all around gear

 

For a RCSB like yours I agree. For a heavy pig Tahoe or a crewcab it's not the best IMO, read my previous post.

 

id stick with the 3.42's because you have the 6-speed. IIRC i read a thread somewhere on here talking about the 6l80e and the 3.42's were on par with a 4l60e and 4.10's. I would do other mods before you start messing with your gears.

I would make sure and get a new driveshaft, too many horror stories on here about them braking. Forget the spacer, start out with a CAI, cam, stall and tune and see where that takes you.

Reading what you are researching, it looks like you are going to be spending a some green, if you got it, might as well just look at some FI there is a brand new procharger in the classifieds going for ~4500.

 

4:10's and be done with it. 3:42's suck no matter how you stack it.

 

3.42s on the 6spd has the same equivalent first gear ratio as the 4l60e with 4.50 rear gears

 

That low? It didn't feel like it off the line on the Yukon I drove with that exact combo, maybe because I'm used to a RCSB 4L60E with 4.11 gears which is a lot lighter. Plus I removed 100% of TM in my truck

 

1st gear take off may be fine but. You do all of your driving or the majority of in 6th gear so you need a gear that will put the motor in it's power band where it does not lug and constantly back shift on the slightest grade. 3:42's are great for mileage but suck for power. Make your own choice but 4:10's have never disappointed me in every truck I've ever owned. They will also put the motor in it's sweet spot and make a 5.3 livable. Especially with 20's all of the extra rotating mass needs that extra gearing when you hit a hill at seventy and don't want it downshifting to hold speed. Good luck just evaluate what people here have said and see how it applies to what you want your truck to drive like and your driving style.