I agree with David for RCSBs. Extended cabs, however, have enough weight to run 4.10s. That's what I run, and have always run. I build boost easily in first, but admitedly have a lot more exhaust pressure than a stock truck .

 

Your 408 pushes alot more air Erik.

 

so some say keep the 3.42s,,, but the weight of the EC actually helps the 4.10s...

Man there are so many choices........

 

Thats what I thought too so I figured my set up, 4.56's, wouldn't let me see high boost in low gears. Last week while doing some street tuning, 1st and 2nd gear, we rolled into it from a light and hit 20psi before the 1-2 shift. Surprised me. I may still look for some 3.55's or 4.10's

 

to bad yours aint a 8.5" 10bolt.... i got some gears on my back seat now.. haha

 

lol - dang it...

 

Thanks for yall input guys!!!
looks like im goin to stick with these 3.42s...

how hard it to just replace the Diff and keep the same gears??

i have everything for a complete install. maybe i can get away with the stock pinion shims that are in there..

 

Turbo's and high stall converters, plus 4.56 gears, do not make the best mix. We're building a 1750 hp, twin turbo 68 RR, with an old school Hemi bolted up to a custom built Turbo Glide. Turbos's love load. Period.

 

ok well i have learned something new...
so the 3.42s are stayin in there. i get to replace the Gernade-80 with the Eaton LSD and go from there.

Thanks yall!

 

There has been NO mention of tire size in this thread whatsoever. Tire size it what determines the effective gear ratio. You could have 3.73" with a 27" tire and it would provide the same effective gear as 33" tires and 4.56's.