Austin97

Yeah that's true, 8:1 pistons then a PI swap would keep you at 9:1 which would be alright for forced induction.

ZachStack

GREAT ADVISE! thank you! what gears would you run in the rear end? just curious...and it is a 4x4. ill keep my eyes open for the trans.

Austin97

I'd probably do 3.73s if you're doing 33 inch tires or less, 4.10s if you're doing 35s. And you know with a 4x4 you have to do the front and rear diffs at the same time or you'll destroy the transfer case in 4x4.

ZachStack

yea. i was thinking 3.73 or 3.55 gears. and i know. i think thats what fried the tcase on my old truck. the guy replaced the rear end and i think the gear ratios were different and it screwed everything up. is there any way to tell what gears are in it now? like are there stamp codes on the diffs?

Austin97

The axle code on the door jamb sticker will tell you what it is. http://www.ford-trucks.com/article/i...r_Decoder.html

Or if you want to test them put a park straight down on the tire and a mark straight down on the drive shaft. Spin the tire one rotation and count how many times the drive shaft spins. If it spins 3 and a half times you've got 3.55s, 3 and 3/4 times and it's 3.73s and so on. It's approximate but you'll be able to tell that way.

ZachStack

well the rear end in my truck is out of an f150 with the 5.4l. idk what the gear ratio was on that...but the truck is suppose to have 3.55 gears in it. thanks for the website. lol.

racin4ds

iTrader: (1)

Stay away from ProChargers street stuff, IMO they are junk. Had a P1 blower on my mustang a few years back and it was being repaired more than it was driven, and was nowhere near as good in quality or performance as the Vortechs. On a truck stay with whipple, hard to beat what the factory uses.

Austin97

Well if you have a 4x4 and replaced the rear with a 9.75" and your 4x4 still works and your t-case didn't explode then you still have 3.55s in the rear..

I haven't done it first hand obviously, but from what I understand if you engage your 4x4 with 3.55s in the front and 3.73s in the back the damage will occur pretty quickly..