How Many Miles Per Tank?

[Skunksmash]

Originally Posted by Firebirdjones

Actually it will drop your rpm quite a bit more than that. When you figure in the lockup converter that drops it down another 300 rpm easily, you are talking close to 2,000 rpm cruise speed with a shorter 28" tire.

3.73's are a perfect match with this setup. Drop the rpm too much in overdrive and you'll find the truck constantly kicking in and out every time you climb a slight grade, not only is that annoying, but it doesn't help fuel mileage.

My truck still has the stock 2:73's in it. So you're saying that even with 3:73's, I'll still be able to cruise at 75 MPH at a decent RPM? If so I'd love to be able to run 3.73's. What a boost that would be. I have a the stock 700R4 on my 87 so I'm not sure what the ratio is on that last overdrive gear. I guess you'd really need to know that to be able to tell me. As for tire size, I just wanna run stock or real close to it.

[Firebirdjones]

Originally Posted by Skunksmash

My truck still has the stock 2:73's in it. So you're saying that even with 3:73's, I'll still be able to cruise at 75 MPH at a decent RPM? If so I'd love to be able to run 3.73's. What a boost that would be. I have a the stock 700R4 on my 87 so I'm not sure what the ratio is on that last overdrive gear. I guess you'd really need to know that to be able to tell me. As for tire size, I just wanna run stock or real close to it.

Yes sir, but I guess "decent rpm" is somewhat different among everyone.

Probably best to use a calculator and decide what fits you best. Your 4th gear overdrive in the 700 is .70. That along with your prefered tire height, and the lockup converter, makes a 3.73 very streetable in my opinion.

You can go to Vexer.com and use their speed calculator, play with tire height and gearings and watch how it affects speed and rpm, it's an interactive screen that's pretty cool.

Hang on and I'll see if I can link it....

[Firebirdjones]

http://vexer.com/automotive-tools/speed-rpm-calculator

Here you go.

I plugged in your .70 overdrive with a 28" tire, converter locked up at 100% efficiency, and 3.73 gears and it says 2200 rpms for a 70 mph cruise speed. Of course it would be lower if you run say,,,a 30" tire...it drops to 2,000 rpms at the same speed.

Plug in some different stuff and move the slider around and see what you think.

[Skunksmash]

Originally Posted by Firebirdjones

http://vexer.com/automotive-tools/speed-rpm-calculator

Here you go.

I plugged in your .70 overdrive with a 28" tire, converter locked up at 100% efficiency, and 3.73 gears and it says 2200 rpms for a 70 mph cruise speed. Of course it would be lower if you run say,,,a 30" tire...it drops to 2,000 rpms at the same speed.

Plug in some different stuff and move the slider around and see what you think.

That seems weird. That's a giant jump in gearing only to have it go up by about 200 RPM's.