bottledbird68

iTrader: (2)

Got a 6.0 swap into my 99 Sierra ecsb. Going with twin 70's in the spring.
Currently truck has 4.10's in it. Running 285/50/20's on ss wheels. Planning a 14 bolt swap anyhow so, should I stay 4.10, or, swap to 3.73 or even 3.42's?
I keep getting mixed opinions. I know turbos like less gear but everything I see pertains to 3,000lb cars. I'm 4wd so truck currently weighs 5200 lbs with me in it and I'm assuming that'll go up another 2-300 with spring time upgrades.
So, looking to hear from those who have been there done that. Keep deeper gears in my whale or lose some gear and really let the turbos work? Placing my emphasis on quarter mile performance over any other criteria.

gamble686

iTrader: (3)

Keep the 4.10s to help you get moving. You supplied your own answer when you mentioned your heavy weight. The 4.10s help a ton and those turbos won't be lacking any load. Plus with those tires around 32" you are about equal to a 26" tire with 3.42s.

sr975j

im in the same boat. im currently working on my truck, 2011 5.3 crew cab 4wd with a pt6766. i have 305/50/20 load range E tires and 3.08 gears. im trying to decide what gear to go with also. thinking about 3.73 or 3.90.

Sam

thunder550

iTrader: (70)

With the 1st gear in the 4L60E I'd go with 3.73's or 3.42's. I have 3.42's in my 1/2 ton d-max and love them. 3.73 was too much. The 4L60E 1st gear is 3.06 compared to the 3.1 in my Allison. If you were in a 4L80E I'd say 3.73, 1st gear is a 2.48 ratio. Your weight is about the same as mine also.

If I could I would probably go to even a 3.23, but I haven't been able to find a set for front and rear.

GMCtrk

iTrader: (27)

twin 70s is a **** ton of turbo, what exactly are you trying to do? If you're going to run it at the track, I'd base your gears off what trap speed you plan to run and where that puts you rpm wise in high gear.

Three6GMC

iTrader: (11)

I run 3.08 gears on my 6 speed 4x4 and I love them... for a 4 speed truck I'd say 3.42s. Also im on a 22 inch rim with 305/40s

oakley6575

iTrader: (5)

Yep I'm with GMCtrk. If you are running twin 70's, its probably going to be track driven. I'd base your gear off of trap speed.

bottledbird68

iTrader: (2)

Track performance is my primary concern yes. However being such a tank I'm really not sure what to expect for times. For now I'll end up running them on my lq4 but once it pops I'll most likely build a 408. If I spec'ed everything out fresh I probably would have gone a little smaller and single instead of twins but I got a killer deal that was too good to pass up from a friend on everything, turbos, wastegates, bov, and a pile of other ls parts cause he wanted it all gone lol. So, I have them and I'm running them. Just means I get to set my sights a little higher

bottledbird68

iTrader: (2)

And it's getting an 80e swap before/when the turbos go on

George C....

everyone wants load which is total bullshit. gear the vehicle as it would be NA with near max rpm thru traps

what do you plan to trap when all said and done?

ill give you an example....we have a mustang that had 373s, we used a 28" tire...we went 8.8@160 crossing traps at 7500...

not saying you want to cross traps at 7500 but im using a 28" tire and going faster then most

look at some of the fastest vehicles around, they have gear in them vs no gear

i just built a lightning that has 373s and will be using a 30" tire and we plan to trap around 150 mph

so why take gear out of a heavy *** vehicle? only thing taking gear out of a heavy vehicle will do is hurt ET and Hurt 60'

when you dont have a trans brake, when you dont have suspension that works for you and you have weight you need as much mechanical advantage as you can get

my old setup in my truck had 410s with 28" tire, ill be installing 410s in my lightning with a 30" tire and want mid 150s