I need a 150+ mph potential but I also want some more power through the gears. I drive a lot of Autobahn here in europe at speeds at least 90-100mph. Which gears would work best for me? Will 3.08's make that much of a difference ? I currently have a 2.73 posi rear end.... would it be possible to just swap the ring and pinion out of a used 3.08 rear since I want to keep my axle ? would it be a lot of hassle ?
Thanks
Alex

 

Alex, what transmission are you using?

 

Sorry, forgot to add that .... Th700

 

so you're going to change from 1.911 final drive ratio (0.70 OD * 2.73) to 2.156 final drive ratio (0.70 OD * 3.08)

70mph is usually close to final drive * 1000. So with 3.08 gears 70mph rpm = 2156rpm, so 140mph would be around 4300?

If you are looking for more power at higher rpms, I would change intake manifold and go with headers. I would do this way before I could make a minimal gear change from 2.73 to 3.08.

Matthew

 

Matthew,
Thanks for explaining me... I'm about to change the intake and runners anyway, just thought 3.08 gears may increase my acceleration a little more. Is there a way of telling what kind of gain I could expect from just that small gear change ?

 

well,

2.73 = ~3822rpm @ 140mph
3.08 = ~4312rpm @ 140mph

I don't know how much hp you make at those rpms. Have you dynoed the car?

I think if I was in Germany, I would go for a mini-ram but not on a 305; I'd go 350 as well....

 

Thanks... well I haven't dynoed my car yet, I plan on doing that after everything is finished.
A mini-ram setup on a 350 would definitly kick butt overhere with so many fast cars everywhere ... but I don't even want to think about the cost over here ..... I was lucky to find a lingenfelter street ram setup that I'm about the put on in addition to a cam and some other small things....