how much higer cruising rpm would that be, right now with 3.73s and 32.8" tires its like 2k ish at 70

 

Well i did the calculator today and with my 33 in tires and 4.56's it will be about 2275 goin 70. as opposed to 1860 now so its a bit of a diffrence. im going to try it out to see what its like and see if its to high. its to bad nobody makes a 4.30 for the front or i would do that. does anybody know if gears from an old 8.5 will work in the new style 8.6 rear end because i know ive seen some posi or something listed for both.

 

yes the gears themselves will work but something like over sized bearings or something is needed

 

hmm, i think i might go with 4.10s then because i have the old rear gears from my obs truck that dont have many miles on them so that would save me some money. does anybody know anything else about doing this? do i use the hole carrier or just the gears? i might have to go take my old rearend apart and do some measuring.

 

Word...Get 4.56. I switched to 4.56 from 3.73 and i run a 285/70R17. I planned on bumpin up to 35's but just put a new set of the same tire. Wish i had done the gears first..you will love it.

I will admit my rpms are a bit higher on the freeway but i can still get 16-17 if i keep it at 65.

Matt

 

im not running that big of a tire but in my last truck with 33's i first went from 3.55's to 4.10's and wasnt satisfied. then went 4.88's and it was just too much. ended up with 4.56's.

on my current setup 4.56's are a lot of gear with the 31.5 inch tires but they work for me (although traction isnt great on street tires) and even though im doing 2550 on the highway at 75. what i like about them is it puts the truck in the powerband so much better for passing and climbing hills.

 

mjcook, how much of an et drop did you see with them? i was at the track last night and really realized how much my low end sucks although i did drop a half second with my ls6 cam. im going to have to take a drive and see what that rpm would be like.

 

i dont know since im waiting for cooler weather...i would guess anywhere from .3 to .5 sec reduction? sort of speculation. my calculations are probably way off but i figured with these gears and a 30 inch drag radial id be trapping around 5500 rpms.

 

Never ran it on the track. As stated before it really keeps it in the Powerband on the highway and hills. Def jumps outta the hole a lot quicker..

Matt

 

how funny...i responded earlier wondering how in the heck does this guy know my name is jcook. weird.