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pixelenvy
Dodge Dakota
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10/22/2002
07:59:15
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 Subject: stupid question about gears
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I'm a newbie to this so bear with me. What are the purpose of gears and what exactly does the number mean when you refer to them .. like 3.42 etc? I figure they take less torque off the truck and give it more speed/acceleration .. if that's the case then would it be stupid to swap out the gears in a 4x4? I wouldn't want to hamper the 4x4 power and towing capabilities of the truck but more speed would be nice. can you guys clear this up for me?
thanks everyone!
-mike
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Clevite 77
GenIII
10/22/2002
08:19:12
|  RE: stupid question about gears
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the number refers to how many times the drive-shaft turns as opposed to how many times the axle or tires turn... 3.92's = the drive-shaft will turn almost 4 times for one revolution of the axle or tires. If you go with a higher number 3.92 being higher than 3.55's the 3.92's will give you more torque/acceleration/pulling power. now the other side to going with bigger gears is your RPMS are higher and you get less gas mileage. with my 3.92's @ 70mph I'm running at 2250 rpms now I think it's just about 2000 rpms with the 3.55's. hope this helps
Line-X Over The Rail Bed Liner
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Hersbird
Dodge Dakota
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10/22/2002
10:56:12
| RE: stupid question about gears
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Another ting to consider is the tire diameter. This will greatly change the effective gear ratio on your truck. If two Dakotas have the same gearing, say 3.92:1 but on is a 4x4 with 31 inch tall tires and the other is a R/T with 28 inch tall tires the R/T will have an overall lower ratio being put to the ground. The 4x4 with it's 31 inch tall tires would need 4.34:1 gears to actually run the same RPM in the same gear as the R/T. A bunch of R/Ts are running around out there with 4.56 gears and the 28" tall tires, and it often helps gas mileage around town or when towing, it only hurts mileage a little on those long flat interstates. A 4x4 with 31 inch tall tires or bigger could easilly run with 4.56 gears and it would be a huge inprovement over 3.55 gears. It would be equal to adding 85 ft-lbs of torque to a stock 5.2 or 4.7.
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pixelenvy
Dodge Dakota
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10/22/2002
11:37:22
| RE: stupid question about gears
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Message:
wow so is that what I should shoot for If I had 31's .. a 4.46 gear setup?
thanks,
-m
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Clevite 77
GenIII
10/22/2002
11:50:48
| RE: stupid question about gears
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Message:
with 31" tires and in drive, o/d off or 4th gear in a 5spd at 70mph you'll be at 3459 rpms
go to this site and at the top is an easy to use rpm calculator, ignore the crawl speed thing. To the left of the calculator is a calculate button. Mess around with that and see which kind of rpms you'll be at, remember if you go too big your motor will be screaming on the freeway, and your gas mileage will really go down the drain
http://www.4lo.com/
Line-X Over The Rail Bed Liner
Home Brew Intake
Dual Exhaust
3923 Autolite Plugs
Krypton 4300K Blue/Whites
Euro Clear Corners
Grille-Tech Grill Insert (Silver)
TPS Set At .705
Removed Rubber Flap
I've used Mobil -1 Full Synthetic Oil And Filter Since I Had 6,000 miles
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pixelenvy
Dodge Dakota
JOIN HERE
10/22/2002
11:59:04
| RE: stupid question about gears
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Message:
what brand is solid for gears?
thanks,
-m
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Hersbird
Dodge Dakota
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10/22/2002
23:09:01
| RE: stupid question about gears
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Go to www.ring-pinion.com they seem really good and carry different brands. They have all the caculators for figuring out ratios as well.
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Hersbird
Dodge Dakota
JOIN HERE
10/22/2002
23:14:12
| RE: stupid question about gears
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Message:
Don't use a OD off on an automatic or 4th gear on the manual to figure RPM on the interstate. There is no reason to cruise down the highway at 70 mph and not be in OD. The RPM at 70mph in overdrive with 31 inch tall tires, and 4.56 gears is only 2387 RPM which is only 100 rpm higher then my pure stock R/T turns at that speed!
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