BeaversTA

Ok guys I'm building a turbo LT1 mostly for street use. The car has a T56 with the following gearing (2.97, 2.07, 1.43, 1.00, 0.80, 0.62 ).. The car has 3.73's in it now and I hear it’s better for spool time to have a higher gear ratio. I'm only going to spin the eng to 6K rpm so I would like for it to spool up fast but still keep good street/strip manners. It’s a stock CP 355 with a small frame T88 at 8-10psi. So what would be better for me 3.23's or 2.73's? The car came stock with 3.23's.

Thanks

02ws6blackbird

i dont now if this makes a diff but i am running an ATI D1SC at 8psi and a have 4.11 and love them!!!!! good luck

BeaversTA

I'm going to use 26" tires.

stevieturbo

What do you want to acheive with it ???

Usually you will gear it so you complete the 1/4 at the top end of 4th gear.
here is a handy gear ratio calculator.

http://www.geocities.com/z_design_st...ion_z28_6.html

Shorter gears in a high powered car, usually end up in tyre smoke, which is why taller gears are preferred.
I'm currently on 3.55, but will be switching to 3.27 if it ever arrives here.
Given your relatively low rpm limit, tall gears would be even better.

vanillagorilla

iTrader: (1)

You are correct on higher gears loading the turbo better, but just remember that if you go with 2.73's, your 6th gear with become almost useless on the highway. I'm fixing to switch my rear gears and it's making me wonder if I should even keep the 6spd if I'm not going to use 6th gear.

BeaversTA

The car is going to be used for street use for the most part. You know stop and go and some freeway fun. I would like to be able to get some traction on the street. My T56 has lower gear ratios than the newer T56's so I'm not sure if I should go back to the stock 3.23's or step down to 2.73's. I have looked at the calculator and at 6K rpm

1st 2nd 3rd 4th 5th 6th
3.23's 48 69 100 143 178 230
2.73's 57 82 118 169 211 272
3.73's 42 60 86 124 154 199
Under boost the car should go thru the RPM's purty quick right.

gametech

iTrader: (1)

3.73's are an excellent compromise between daily driving and raping your bud's at the strip.

stevieturbo

Depends how fast you go.....

I thought the 3.55 would have been ideal for me. But given I am shifting into 4th at the 1/8th mile, I am hanging onto 4th gear for the final 1/8th mile.....

I defo need taller gears, as 4th is taking me way beyond peak power.

But 5th and especially 6th gear is a very valid point. At the minute my 0.5 6th gear is very usable above 40mph.
With the 3.27 it will be less so....

Not a problem, as I am having Joe build me a new T56 with the 0.8 5th and 0.62 6th gear, so both should remain good.

Frost

iTrader: (45)

Gearing numerically lower is going to be REAL HARD on the tranny, clutch, and drivetrain.... ESPECIALLY with a turbo

Darren P

iTrader: (1)

I have 3.50 on my turbo car and I love it

S99TA

i have 4:10s w/26 inch tires and love it go through the traps just before red-line (6800 rpm)

stevieturbo

The requirements for a car with a lot of power ( ie n/a vs blown ), do change substantially though.

On the road, on normal tyres with my 3.55, I can light the tyres up with ease in 4th gear...

If I had something like a 4.10 diff.....that would probably extend to 5th gear.

Cars with a lot of power/torque, can make better/easier/efficient use of it, with taller diffs.

gametech

iTrader: (1)

I still want to hear about stevieturbo going through 4th in the 1/8th. How fast is that?

BeaversTA

so going back to the stock 3.23's would be the way to go. I know when the car was NA it would go thru 1st an 2nd quite fast with the 3.73's so on boost it would never get any traction.

stevieturbo

I am shifting into 4th at the 1/8th, circa 112-113mph