[Hit Man X]

I'm HIGHLY considering regearing this Z I have here to 4.56:1 gears with the 33" tires. That'd give me about 2300-2400rpm @ 70mph. Do you guys think that is too high for a cruise RPM?

Now I'm at a poor 1800rpm with my 3.73:1 gears. My truck drags on the freeway and around town.

What does everyone think? I found someone locally that will help me install the gears (front, rear, and Eaton for about $150/axle!) too.

Thanks!

 

[Black_Chrome]

i guess gas isnt a concern

 

[GMCtrk]

I say go for it!2300 rpm is just fine IMO....I mean come on, most 4 bangers do 3-4k highway crusing

 

[Hit Man X]

Well 1800rpm @ 70rpm is dragging ass. Most new vehicles tach up around 2000rpm @ 60mph.

4.56:1 gears with 33" tires is pretty damn close. Recall lower RPMs do not equate to better economy always...

 

[Hit Man X]

I say go for it!2300 rpm is just fine IMO....I mean come on, most 4 bangers do 3-4k highway crusing

Yup, my WRX does about 3000rpm @ 75mph. It's also ~3100lbs and has like a 25" tire.

The cruise RPM of the truck with 4.56:1 gears is about what a stock 6.0/4l80E HD does with 30.5" stock tires...

 

[Whifflebat]

I dunno if I would go to 4.56's, I'd think you'd be sucking down a shitload of gas. Just look at what zubyc was getting with his 4.88's and stockers, 4.56 isn't much different. :imo

Also, on my truck I get much better mileage at 1700-1800 rpm than 2000 rpm.

 

[Hit Man X]

Well it takes more fuel to run 80-85mph @ 2000rpm than it does at 70mph @ 2200rpm. You drive a brick...not a car.

 

[Rednecked_4x4]

id say 2600 is the max id run an engine at highway speeds.

 

[Whifflebat]

I run 70 mph at 2000 rpm.... 65 at 1800, my gas mileage is 2-3 mpg better at 65.

 

[Slvrpismochevy96]

On my silver truck i have 4.88 and 35's and i like it...and its a Gen1 vortec 350...i only get about 11mpg in it though. My new truck has 4.10 with 31's and its perfect, 2000rpm takes me about 65mph......4.56 and 33's will be a little bit lower than my setup and with the extra weight of a 33 compared to my tires you might as well do it :imo ...and if you get 35's in the future you will already be set

 

[brodystruck]

RPMs isnt the main factor in MPG. It's engine load. Effciency is related to this, the engine's vacuum it's pulling is also a direct relation. If your engine is struggling and bogging at 1800 RPMs it very well might get better gas mileage and a higher RPM.

Even if you geared your truck to run as efficiently as possible on the freeway, your gas mileage still won't be that good because of the bigger tires.

Around town mileage will prolly go up because you are making it 'easier' for your truck to get up to speed, yet still keeping plenty of gear and power to cruise efficiently.

I had a vac. gauge on my last car, it was a huge tattle-tale. Gives it away to your passenger how much you are getting on it. 0"=WOT. I'd get around 18" cruising though.

 

[Hit Man X]

brody...that's what I couldn't explain. It's easier for the motor to move the truck at slightly higher RPMs.