highway RPMs with 456s

[demerson2]

Does anyone have an estimated RPMs for the highway at 55 and 65 mph with 5.0 efi/435trans/36 inch tires/456 gears?

 

[Devin]

Have at it:

http://web.archive.org/web/20050204061805/home.comcast.net/~jcmiley/bronco+gears.html

 

[fromme]

At 65 I'm about 2800 rpm

 

[Daddy4zack]

60mph @ 2700-2800

 

[ol gray mare]

Have at it:

http://web.archive.org/web/20050204061805/home.comcast.net/~jcmiley/bronco+gears.html

Now that's cool!

 

[22213evl]

woohoo it says I can do 101 mph at 4000 rpm.

although I think that would end badly.

 

[recoiljunky]

woohoo it says I can do 101 mph at 4000 rpm.

although I think that would end badly.

I ran mine up to 5500 rpm in high gear with the exact same set up last month on the dyno meter.

Made me nervous as hell. Truthfully, I'm not sure it's safe to spin TSLs that fast.

 

[malonejy]

That is a cool calculator. That should be on all the vendors web sites. At least those that sell gears.

 

[Devin]

That is a cool calculator. That should be on all the vendors web sites. At least those that sell gears.

That was put together by a guy that used to be on the site. He had an even more updated version of it. But, he sold his Cummins-powered Bronco and left. Haven't heard from him in years.

 

[67Stallion]

Not sure how accurate that caculator is, checked my speeds and rpms with gps today, i have 31,s and to be with what the calc says, i have to plug in 28 inch tire!

 

[Devin]

Not sure how accurate that caculator is, checked my speeds and rpms with gps today, i have 31,s and to be with what the calc says, i have to plug in 28 inch tire!

I guess I have never checked the math on the calculator (I didn't make it). However, you mentioned that you have 31's. Did you ever change your speedo gear? Do you still have your original gears?

 

[HoosierDaddy]

Measure your tire ... that is where the majority of the difference will be. Most tires are not as big as they are stated.
What tranny ?
check other gear ratio calculators out there.
http://www.4lo.com/calc/gearratio.htm
http://www.ramblerman.com/blazer/gearcalc.htm
http://www.ringpinion.com/Calculators.aspx

EDIT : the math on all four calculators pretty much matches , usually just rounding differences.

 

[El Kabong]

Here's another Gear Ratio Calculator. With this one you can enter 2 different combinations & see the results side by side.

 

[DirtDonk]

Two things come to mind that lead to slight inconsistencies. Pretty slight actually, but they're there.
Some automatic transmissions have more "slip" at speeds than others do. That would lead to the tach reading just a bit higher than the calculator would lead you to expect. I've found Bronco C4's can be 200 to 300 rpm higher at freeways speeds than a manual.
The other is what HoosierDaddy mentioned. When figuring your tires, use the loaded-radius for your calculations. For that, measure just from the center of the hub, down to the ground. Then double it.

You might find your 31 is actually closer to that 28 the calculator says.

Paul

 

[br0nc0xrapt0r]

Ive seen a lot of charts before but not that calculator! thats cool and deff helps my choice I am going with 4.88's

 

[67Stallion]

I like that calc Devon put out there, your right DirtDonk, my 31,s with new like mudder tread measures 29 1/2 horizontal and 29 in. vertical, and plug in 28 inch tire in chart and its the closest to my gps readings. They should be able to make a gps speedo by itself to stick to the windshield much cheaper than a gps tomtom or what ever. I would rather use that, than looking down at a speedometer all the time! It wouldnt matter what gears, tires, trannys your were running, you would know the exact speed your going! Anybody know the rpm sweet spot for a 67 289, stock, 9.3 compression motor for cruising down the freeway, its hard to tell, it runs strong at any rpm, its stock everything, just rebuilt about 32 years ago and maybe 10,000 miles on it!

 

[demerson2]

thanks for all the info.....that is a good chart.....i'm able to explore all gear and tire opportunities....