i was wondering if someone could compare the rpm's in a 4l60e with those two gears. i have 3.42's waiting to go in but want to make sure those are what i want. i will be shifting at about 6200 rpm's and launching with a 3000 stall converter. i just don't want to cross the line and still have some rev's left with the 3.42s. and i don't want to have too much gear with the 3.73's and have trouble lauching and do NOT want to shift into 4th. i would love to cross the traps at around 6000-6200 in 3rd. thanks guys

thomas

 

It depends on the height of your tires and how much they "grow". Typical F-body street tires are ~26" tall and street radials son't grow much at all. With a 26" tires 6,000rpm is 135mph using 3.42's and 124mph with 3.73's (assuming no converter slippage).

Bias ply drag tires grow, and that needs to be accounted for. What kind of trap speeds are you expecting and what tires are you using?

Rich Krause

 

i don't know about the times since i havn't ran the car yet. but i would guess around 110?? i am running the xe230/236 with ton's of boltons and stock heads w/ 2.00/1.56" valves.

for tires, i would like to run a 26" et street slick mounted on prostars, 15x8.

anything else ya need to know?

 

You won't be ourtunning 3.73's with those mods and a 26" ET Street. That tire with 3.73's will be good to nearly 130mph at 6,200rpm and it won't go that fast. Go for the 3.73's.

Rich Krause

 

Just done the swap from 3.42s to 3.73's. I picked up about 350-400 rpm going to the 3.73's. I'm trapping about 6150-6200 rpm.
I run 26x10x15 M/T Drags. Hope this helps.

The only problem I have right now is the stall is going have to get changed.

 

ken

why will your stall have to be changed? are you haveing traction problems?? i am getting ready to purchase my stall and want to make the right decision on stall speed. i plan on going with a 3.73 gear as well.

what are you changing your stall speed to?

thomas

 

You figure the % change between the 3.42 and the 3.73.
Take this number and ADD it to the current 3.42's RPM through the traps. This is how I do it and it will get you in the general ballpark.

This one works out to a rounded off 9% difference/increase in RPM through the traps.

HInk