Quote:
Originally Posted by mike's1965
My Corvette handles 6th gear just fine, it has the T56 with .50 6th gear ratio, and 3.42 rear gears...
|
The Corvette is *slightly* more aerodynamic and weighs less. Aero makes a huge difference in how easily a car/truck can cruise over 55-60 mph. I drove from SC to AZ and back earlier this year and paid attention to cruising speed vs mpg. My car gets 40 mpg at 65-70 mph, 35 mpg at 80-85, and 30 mpg at 90 mph. It's geared well for the interstate, but it's shaped like a box and the added aero drag really makes the engine work harder with increasing speed. I added a cam recently that shifted the torque curve up a bit and it now it doesn't like fifth on the interstate with the A/C on, especially up hills- I have to drop back to fourth. So it's very possible to have too much overdrive in something that not very aerodynamic, especially with a cam that hurts low rpm torque.
I'd stay away from a NV4500 in a street truck, they shift like a tractor and aren't very fun to drive. We have one in a flat bed with a 454 and it's great for towing and does good on the interstate but the shifts are really clunky- not ideal for a fun cruiser.
A T56 would work well with 4.10 or 4.56 gears. Look into remote shifters with a high hump tunnel if you go with a F-body T56, that's a better option IMO than doing the internal shifter relocation. A Magnum T56 would have the forward shifter location already.
A little bit of rpm on the interstate isn't going to hurt anything. I grew up with early VW bugs that run around 3800 rpm at 70 mph. My old Miata did 4000 rpm at 80 in fifth gear. My Festiva does 3300 rpm at 80. It's not going to hurt anything to run some rpm on the interstate, your engine isn't "straining" or hurting itself from not having overdrive.