I'm still working on the build to replace the 2.8 in my car with a slightly built up 3.4. I'm shooting for 180-190 HP, and from what I understand, that's asy for the 3.4

I'm also thinking of upgrading the rear end of my car from a 3:42 to a 3:08, the same one that came on the V8 5 speed cars. The goal is to drop the highway RPM down below the 2600 at 70MPH that I have now. I'm not sure what the 3:08 would do for me, is there a formula I can use to figure that out?

 

http://www.ringpinion.com/Calculators/Calc_RPM.aspx

 

Interesting. It gave me 2337. Only a drop of a little more than 200. thought it would be better, but It's still good to know

Thanks

 

Consider ;
stock a V8 has a LOT more torque ,lower down than a V6 so it can pull a taller ( not faster ) gear.
When you "hot" a engine up you tend to loose bottom end so the engine has to rev higher before it gets into it's working range ,
the main reason you see " low" gears like 3.73 / 4.11 in Hp cars.

Over gear the car ( too tall a rear ) and the engine will be below it's working range and probably use more gas.

 

Interesting, thanks

 

You don't want the 3.08 with the V6. Chevy used the 3.08 with V6 in the early years and corrected their mistake by using primarily the 3.42 gear for V6 after 83. ( many 3.23's out there too ! )

IMO; the 3.42 gear in your car is a GREAT all around gear ratio,.... for V6 or V8 cars. I'd leave it and focus on other priorities - like getting that motor swap finished and the car rolling under it's own power again ! Once your behind the wheel and driving again you can feel out the existing drivetrain ( rather then theory ) and then make a better informed decision about changing the gear / rear.

 

Actually the original 2.8 is still going very strong. The car runs like brand new, but I've got a 3.4 in my garage that I'm planning on using someday. I'm waiting on a sign that the 2.8 is getting tired, I hate pulling such a good, smooth engine

 

good points.