Gear ratio decision... need some advice

[toms57]

I am putting a ls1 in my 57 with a 4l60E.
I currently have 2 options of rear gears to install. I need to make the decision soon so I can get the computer set up.
I currently have a 3.08 standard gear that is good and also have a 3.33 Posi available.
My concern is if the 3.08 is too tall a gear to be putting against an overdrive transmission. It is strictly a cruiser, no street or strip racer. I drive the car lots on road trips so mileage is a vital concern. But I am also concerned that a 3.08 may tend to lug the engine at cruising speed.
The alternative is the 3.33 which would be a little higher rpm at highway speed, but possibly will allow the engine to pull it a little better.
Am I overthinking this too much?
Tire size is 225-70-15.

Any thoughts?

Tom

[chevynut]

Here's the gear ratios of the 4L60E. Plug them into a calculator like the one on Richmond Gear's website. There may be one here too. Plug in your rear tire diameter, and look at RPM versus speed. I'd shoot for something around 2000 +/- 200 RPM at highway speeds, like 75 MPH. Then look at your first gear ratio.

3.08 and 3.33 really aren't that far apart...only 10%. With it being only a cruiser, I think the 3.08 gear should work well. It should put you right at 2000 RPM at 75 MPH. If you want a little more street performance, go with the 3.33.

http://richmondgear.com/2.html


Gear ratios:

1	2	3	4	R
3.059	1.625	1.000	0.696	2.29

[Bihili]

Another calculator:
http://tri-5.chevyrides.com/rpm.php

The Posi wins my vote,
not because of the ratio but because of the fun factor.

[Rick_L]

I don't think the LS1 will notice the difference. Lots of factory LS cars, even trucks are geared with a 3.08 or close.

[567chevys]

Hey Guys there is a Gear Ratio calculator at the top of the page , Also there is one in the library .

Thanks Sid

[toms57]

Thanks,
The calculator puts the 65 MPH rpm at about 1700 - 1800 . I think that I will probably do the 3.33 to keep it up there a little. I also suspect that the LS may not really care.
The difference between the 2 ratios was only a little less than 100 rpm, so MPG shouldn't be severely affected either way.

Tom

[Maddog]

3.50 WOULD PROBABLY BE BEST SO DO THE 3.33

[chevynut]

The calculator puts the 65 MPH rpm at about 1700 - 1800 .

So you're the guy everyone has to drive around on the freeway?

[toms57]

I guess I would be that guy. Unfortunately there are not lots of freeways in our area. Mostly posted at 65 MPH around here. When I do get on a freeway I prefer to flow with the traffic.