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Josh
Dodge Dakota
11/27/2001
12:48:47
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 Subject: 3.92 & 3.55 rpms
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Message:
just wondering if anyone could tell me what the rpms of the 3.92 and 3.55 (5spd 4.7)running about 80mph and the approximate gas mileage difference.
thanks
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Will
Dodge Dakota
11/27/2001
15:40:48
|  RE: 3.92 & 3.55 rpms
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Message:
I've got the 4x4 Slt package which gives you larger wheels than with 2wd. My RPM at 80 is about 2500, not bad. Go with the 3.92. Think about it, the RT is a 3.92 and thats all I needed to know when I made my choice.
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Boomer
Dodge Dakota
11/27/2001
15:48:03
|  RE: 3.92 & 3.55 rpms
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Message:
I run at 2000 at 80, I switched to 3.73's. It was a cheaper bid for me from going to 3.92. I had the 3.55 and kina liked them, but I really like the 3.73's. They still have a highway run and good pull off the line.
Boomer
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Matt Barret
Dodge Dakota
11/27/2001
16:43:22
| RE: 3.92 & 3.55 rpms
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Message:
Josh, you should see a 300 rpm difference in the 2 gears @ 80 +/-, thats asumming you are using the same tire diameter.
So with a 3.92 gear, 28" tire, and running 80 you should see approx. 3000 rpms and if you had the 3.55 gear you should see about 2700 rpms.
I think I did my math right, someone correct me if I am mistaken.
Matt
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Dakaty
Dodge Dakota
11/27/2001
16:55:18
| RE: 3.92 & 3.55 rpms
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Message:
The difference between a 3.55 and a 3.92 gear is that the drive shaft will have to turn .37 (about 1/3) of a revolution more to maintain the same speed at the rear wheels.
This would mean that the engine would run about 10% faster, assuming a 1:1 ratio of engine speed to drive shaft speed.
I'm not sure what the ratio of engine speed to drive shaft speed is. I think it is less that 1:1 on the Auto overdrive trans.
Go to Richmond Gears webb site. They have a calculator which will assist in estimating engine RPMs at different speeds.
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josh
Dodge Dakota
11/27/2001
21:05:46
| RE: 3.92 & 3.55 rpms
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Message:
thanks for the help
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