Gear Change RPM range query

[geo815]

It's been a month since I've had the car down the road :mad: due to the tons and tons of mag-chloride the geniuses out here love to use every time it snows. Of course, now I'm contemplating a gear change and I can't remember what my tack said while doing the Colorado state speed limit (75 MPH). Quite frankly, I can't remember if I've ever had the car at that speed before - a little bit slower than that, of course (Wanna buy some ocean front property in Denver?).

Before I plunk down the dough for the rings, I'd like to know where my highway cruise RPM will be at 75 MPH if I ditch the stockers in favor of 4.10's. I'm still running the stock meats.

[Vortech347]

Don't fear the gear. :) I kinda kick myself in the ass for not doing 4.10's. But it was free... :)

We have 4.30's in our cobra and sit at 3050rpms @ 80 and around 2800rpm @ 75. Gas MPG sure isn't an issue thou. Driving it cross country at 80-85mph It knocked down 21mpg. Daily driven it gets around 19mph and cruising at about 75 it gets freakin 25!!!

I've been told 4V mod motors get pretty good mpg as long as they're kept under around 2700 cruising.

[99SVT]

At 75mph you'll be turning just under 2500rpm with 4.10. With the stockers you're at about 2100rpm, not that much of a difference.

[Vortech347]

Yea thats not bad at all...with 3.73's I think the MM is at like 2300ish @ 75.

[Pat]

At 70 MPH my MM is at 2500 RPM with the stock converter and 4:10s. With my new 3500 stall speed converter, my RPM is at 2400 @ 70 MPH.The A/C makes a huge difference in gas mileage. Without the A/C on I get somewhat less than 24 MPG @ 70 MPH. In town I get about a tank a week 'cause I always have my foot in it.Pat

[geo815]

Thanks. Looks like I know what I'll be doing this winter.