allright you see my signature that is everything i am running with a p255-60r15 back tire. i am seriously considering a 3:73 swap and was curious as to what it would do to my acceleration and of course gas mileage . my mecahnic said that those gears would really help my acceleration with the motor i have. currently i am at a 3:08 posi rear. my brother had a 94 lt1 that had 3:73's and everytime i drove in it i almost pissed my pants!! haha gotta love 400 horses anyways thank you all .

 

I would look at 3:42's....They would match your combo better...any I dea on cam specs?

 

I didn't see what type of induction you had, but my personal preference would be that if you have TPI, get 3.42s, and if you have a Carb, get 3.73s. There are tons of other factors to consider, but as a general rule, thats where I start.

 

thats the rule i heard also..

 

15.970 to 15.294, enough said

 

you went from 3.08 to 3.73 and got that big of gain?

 

2.73 to 3.73, this is also with a crank pulley and 4* more timing advance, so i say the gears and posi gave me a good half a second, i think if i can get my 60 foot times alittle lower, and manually shift, i could be in the 15.0x-15.1x range.

 

Would it be worth changing from 3.23s to 3.42s? I don't wanna go 3.73s cuz it would probably kill my gas mileage and I drive the car everyday. Just wondering whether or not this difference would give me any significant improvement in acceleration with the mods I have in my signature. Also I will be installing headers soon.

 

i have a 600 cfm holley carb. my mechanic told me that 3:73's would wake up my car. what do yall think

 

my car is a daily driver and i havent notice a significant loss in fuel mileage. I drive 250 miles home from school every once in a while and only use about 5/8 of a tank, thats a good 25 mpg on the highway, and i probably get about 13-15 mpg in the city. (on 91 octane)

 

3.73's aren't going to 'kill' mileage. You are running a taller than stock tire(255/60R15), which makes the 3.73's with a 27 inch high tire 'like' having 3.53's. So the 3.73's aren't as 'radical' as you might think. Get em', they are lots of fun--I went from 3.08 to 3.73's.

 

How about with 245/50R16s?

 

What rpm do you shift at? With the stock TPI, 3.42's might be a better choice.

 

Under light throttle about 2000, a bit more throttle about 3000. Never had the car to WOT. On the highway I usually do 80 at about 2400 RPM, and get about 21 MPG. How would all this change with the 3.42s?

 

If you don't use WOT, why are you wanting to switch the gear ratio? The rpm where it shifts is going to be about the same, the change is your speed when it shifts(mph will be lower) and the increase in the ability to accelerate(especially off the line).

 

I went from a 2.73 to a 3.73 on my car and I love it. My car is a daily driver too. I have a 305 TPI and 245/50/16 tires. I went from about 17 mpg to about 15.5 - 16 mpg. I cruise at about 2500 rpm at 75 mph and 2000 rpm at 60 mph. The only disadvantage might be that it makes it a little harder to take off in the rain because the tires spin a lot easier.

Took me about 6 months before I finally got my speedometer straightened out though.

 

I probably won't end up changing them. I was just curious as to how it would affect my shift points and speed. I do a lot of highway driving and I'd like to keep the gears I have now so that the engine doesn't rev higher at the same speeds. I know this is more of a racing application, but if I ever retire this car from daily driving, which I'm hoping I do someday, then I'll keep this information handy.

 

in an engine with a big cam that likes high rpms proper gearing is necessary to "re-aquire" lost low end torque.

You can add torque through gearing, but not horsepower. and horsepower is what makes 1/4 mile times. gearing just adds torque. lots of it.

going from 2.73 to 3.73 in my 355 with a blower dropped me from 14.5~ to about 12.1 in the 1/4 mile. My MPH went up slightly, but not much. its all about that torque. going faster, faster.

My car was a slug off the line before 3.73's. the tires wouldnt even spin when i power braked it. I didnt lose anything up top, I still shift @ 6500 Rpms, but the torque advantage of gearing makes the car SO much faster. and more fun to drive. I have a video of the car lauching on 2.73's... its pathetic.