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WHISKERS
Dodge Dakota
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12/30/2006
21:19:52
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 Subject: TECH QUESTION, ANYONE KNOW??
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DODGE DAKOTA WITH THE 5.2 4X4.
4.11 GEARS AND 33 INCH TIRES ..
IN 5TH GEAR WHAT SHOULD MY RPMS BE @ 65 MPH??
THANX IN ADVANCE...
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Manny
Dodge Dakota
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1/01/2007
03:36:20
|  RE: TECH QUESTION, ANYONE KNOW??
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Not enough info given. RPMs of what: engine? driveshaft? tires?
To perform the simple calculation, need ratios of 4th and 5th gears in transmission and need exact tire size from sidewall.
Engine size not important.
4x4 not important.
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prickhead
Dodge Dakota
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1/01/2007
13:48:09
| RE: TECH QUESTION, ANYONE KNOW??
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so in other words you have no idea....
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Manny
Dodge Dakota
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1/01/2007
14:19:42
| RE: TECH QUESTION, ANYONE KNOW??
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No need for the attitude.
I can give you the information you want, but without the transmission ratios and exact tire size, there's no way to accurately figure the engine RPM at any speed. 4th gear should be 1:1 (or very close to it), but 5th will be an overdrive, meaning 1 revolution of the engine equals more than 1 revoluton of the driveshaft. Without the additional information, it's only a guess.
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SteveJ
Dodge Dakota
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1/01/2007
17:48:17
| RE: TECH QUESTION, ANYONE KNOW??
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Manny's right. More data is needed, unless you don’t care about accuracy.
Here's some ball-park figures.
A 33” diameter tire has a circumference of 103.67”.
(Now we convert MPH to inches/min)
65MPH = 1.08 miles, x 5280 = 5702 feet, x 12 = 68428 inches/minute.
A 103.67 inch circumference tire has to rotate at 660RPM to cover 68428 inches in one minute (68428 / 103.67).
660 x 4.11(gear ratio) = 2713 RPM of the driveshaft.
If the transmission gear ratio is 1:1, then the engine is rotating at 2713 RPM also.
Once you find out the 5th gear ratio, multiply that by driveshaft RPM, and that will give a rough estimate.
For example, say 5th is 0.9:1. 0.9 x 2713 = 2441. So the engine RPM at 65 in 5th would be approximately 2440.
Without knowing the exact tire size, it's impossible to be accurate, because a 33" tire is almost never more than about 32.5” tall.
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KOKBREATH
Dodge Dakota
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1/04/2007
18:52:52
|  RE: TECH QUESTION, ANYONE KNOW??
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5TH GEAR IS 0.73
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WHISKERS
Dodge Dakota
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1/04/2007
18:56:18
|  RE: TECH QUESTION, ANYONE KNOW??
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WHAT WAS THE QUESTION??????????????????????????
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SteveJ
Dodge Dakota
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1/05/2007
00:50:48
| RE: TECH QUESTION, ANYONE KNOW??
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So .73 x 2713 means engine rpm is 1980.
Again, this assumes 4th is 1:1.
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Manny
Dodge Dakota
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1/05/2007
12:45:16
| RE: TECH QUESTION, ANYONE KNOW??
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Thanks for covering, SteveJ. But the way you figured it, it shouldn't matter what 4th ratio is.
Using your method, engine RPM can be found for any transmission gear ratio after you figure out the driveshaft RPM.
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SteveJ
Dodge Dakota
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1/06/2007
15:14:00
| RE: TECH QUESTION, ANYONE KNOW??
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You're right.
Didn't really analyze it all that much, just slapped some simple math together, hoping someone would find it useful.
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WHISKERS
Dodge Dakota
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1/13/2007
19:22:50
| RE: TECH QUESTION, ANYONE KNOW??
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WHAT WAS THE QUESTION??????????????????????????
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