I'm looking on swaping my 4L70e out of my 07 VMax to a 6L80e. I'm also adding a Trick Intercooled 76mm Turbo kit. My truck currently has 3.73's that will my make it great for drag racing with the 6L80e's crazy tall first gear. But I rather have my truck reving less then 2000rpm on the highway when I'm cruising at 80mph. Now my truck is at 2400ish at 80mph with the 3.73's. My last truck was a Sierra Denali with 3.42's and reved 2000rpm @80mph. My question is: Will the truck have enough power at a projected 500rwhp to propel my truck without lugging or constantly down shifting on the highway to maintain speed on slight hills if I change the gears to 3.08's? I know it will have plenty of power in the upper rpm's but I wonder how will it drive on the highway between 1500-2000rpm? What do you guys think? Don't think 1/4 mile, think mpg's....

 

Will the current PCM control the new tranny?

 

My truck came stock 6 speed with 3.08s and it doesn't down shift at all. It has plenty of low end to stay in gear even over hills at 70. That turbo will stay nice and spooled up with 3.08s. I know on my truck when I had the 5.3 and mp72 I would be just over 1psi at 70 cruising.


Here is just an old quick clip of how quick the turbo would spool with the 5.3/6l80 3.08 gear combo...

 

Google fbody gear calculator. It will give your estimated mph and rpm by gear

 

IMO 3.08's would be a sweet combo if you do alot of highway miles...if in doubt you could go 3.23's

 

If my 4.8 4L60 with 3.23s (with heavy 22s to boot) can cruise down the highway without lugging and hardly ever down shifting, your 6.0 and 6 speed would be just fine in my opinion. I'm boosting soon and keeping the 3.23 gears, I think yours would love the 3.08s and boost.

 

Just don't oversize the turbo or you'll freaking hate it....

 

Dont think they make 3.08s for the 9.5" 14 bolt. As long as you get a good converter that can stay locked in boost then it should relaly never struggle with hills, since itll spool whenever the load of the hill hits the motor.

 

X2 forgot your a v max truck and I have checked no 3.08s for the 9.5 14 bolt. I'll be willing to trade you my 10 bolt for your 14

On another note im sure you have easy access to a 8.6 10 bolt, but if you ever want to sell you 14 bolt or know of one for the nnbs trucks let me know.

 

3.42s is highest gear Ive found for them. Im just changing my gear ratio by adding taller tires