spina74

iTrader: (12)

Ok, so i put a 9" in my car from my stock 3.42 10 bolt....the center section I bought came with gears. I was going to check the ratio before install but it slipped my mind. The guy i bought the gears from said he did the whole turn the yoke and count the yoke turns per ring gear revolution. He claimed it was around a 3.55. Now when I drove the car it feels a whole lot different than the 3.42's. From other posts I've read going from a 3.42 to 3.73, you'll barely notice a difference so I'm assuming the same with the 3.55's. My questions is what RPM are you 3.55 gear users at at 70mph, as well as the 3.90 gear guys at 70 so I can see what gears i really have. My pcm is currently tuned for a 3.55 ratio with the correct tire size.

dkota1968

iTrader: (1)

Just got my 390 set up, a lol below 2000 at 75. Stock 275 tire also

3.8redbird

iTrader: (3)

What size tire are you running? What gear? Trans?

dkota1968

iTrader: (1)

6spd, 275/45/17, 3.90s

3.8redbird

iTrader: (3)

Sorry I meant the OP

spina74

iTrader: (12)

315/35/17, unknown gear, t56, and pcm is tuned to the tire size and 3.55's

bigblock704

iTrader: (1)

Can always pull the chunk and physically count the teeth..

dkota1968

iTrader: (1)

I forget how but i believe theres the count how many rotations of the drive shaft per one full rear rotation.

I found it try this it should be close:
http://www.ehow.com/how_5969377_dete...one-wheel.html