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no ford trucks
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Discussion Starter #1
I just installed a tach on saturday and at 60 mph I was running 2300 rpm. I have 33X12.50 BFGs and 15X10. No lift, but can anyone guess at what type of gear I may have, and is that a high rpm? It has a C6 in it and no full time 4X4. Thanks in advance. :rockon
 

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www.easttn4x4.com
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2,191 Posts
Not sure on the gear maybe 4.10. That seems a little on the high side, which is good if you ever plan to put on bigger tires.
 

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Charlie don't surf..
'92 Ford Bronco XLT
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15,074 Posts
I'm guessing 3.73 with the 33 tires.
 

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Welcome to the jungle
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678 Posts
That is correct. 2300 RPM at 60 mph on 33" tires means you're running 3.73 axle gears. In "High" range, the t-case ratio is 1:1, as is the tranny in third gear. Therefore, your axle provide your only gear reduction on the freeway.

60mph=1mpm=5280fpm=63360ipm

63360/(33x3.14)=rpm of tire

rpm of engine (2300)/rpm of tire(611.465)=3.76 <---{Gear ratio} w/ a little rounding error
 

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no ford trucks
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721 Posts
Discussion Starter #5
I was going to sell the bronco after I got frustrated with it, but with this kind of help, how can I. You guys are great. I look at these forums everyday and try to help when I can. Thanks a lot.
 

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shibby
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4,828 Posts
No way to tell unless you state the exact loaded tire diameter. Using a guess of 31.5" loaded height, I come up with 60.5mph for a 3.55 ratio which is most common.
 
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