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V8 Dakotas
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zamboni man
Dodge Dakota
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1/13/2004
02:20:48
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 Subject: Gear Ratios
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Can someone explain the difference between a 3.55 and a 3.92 gear ratio and why the limited-slip is so much better?
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posi man
Dodge Dakota
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1/13/2004
08:16:03
|  RE: Gear Ratios
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Gear ratios are simple. the higher the number the lower the gear. A 3.55 unit means that the driveshaft spins 3.55 times, and the tires spin one full revolution. A 3.92 means the driveshaft will spin 3.92 times to get the tires to do one revolution. The lower gear is better for acceleration, but makes the top speed lower. A 4.88 rear end would give you neck breaking acceleration, but your truck would top out at like 85 mph. Where with 2.76 gears your truck would be a dog off the line, never climb a hill, and probably never have the balls to spin the tires, but would go like 65 in first gear. I am just guessing on the speeds here, I am just using them as examples. As for limited slip/posi-traction, both tires will spin when you hit the gas, giving you twice the traction of an open differential, making your truck faster off the line(and more fun around corners at full throttle). The reason it is more fun, is because when both tires break loose in a corner, the ass end of the truck goes sideways, It looks cooler, and is much more fun(unless a cop sees you do it.) An open differential will usually spin just one tire, and cause people around you to laugh, because you dont have limited slip. Occasionally an open diff. will spin two tires, but never when you want it to, and it is only around 5% of the time. I'll stop rambling now.
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.boB
Dodge Dakota
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1/13/2004
10:41:03
| RE: Gear Ratios
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An open differential will direct power to the tire with the LEAST traction. It's cheap, it's easy, and it lasts forever. For the vast majority of drivers that works just fine. If you live where it snows, you know what it's like to get stuck, or have one wheel spinning while you're trying to get up the hill. Oddly enough, that can be a good thing for some people, as the non-spinning whell acts like a rudder and keeps the back end from fishtailing around.
Limited slips/posi's direct most of the power to the wheel with the MOST traction. Great for getting through the mud/snow/sand when you need to. But it can make both rear tires spin and the truck will fishtail. Requires a slightly different driving technique.
I never could understand why anybody would by a 4x4 w/o LSD/Posi. Doesn't make sense. The front differential is always open; can't put LSD/Posi there. So on many 4x4's you have two open differentials. Get one side of the truck in the snow/ice/mud, and you're going nowhere. All the power is directed to the two wheels without traction. If the rear is LSD, then at least one tire will grip, and that's usually all you need to get moving again.
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DavidH
Dodge Dakota
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1/13/2004
12:58:56
| RE: Gear Ratios
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I don't mean to sound too uninformed, but how do you determine your gear ratios? I bought my 95 5.2L 5 spd used and that was not one of the questions I thought to ask. Also I was wondering about the diff, how do I determine the size. Thanks for all of your help.
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b1llyw
GenII
1/13/2004
14:40:04
| RE: Gear Ratios
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Great explanations guys. Hey DavidH, on my '95 the gear ratio and whether or not you have the "anti-spin" differential as the factory calls it are listed on a sticker on the underside of your hood.
Bill White - KRC Performance
'95 CC 4x2, SLT - 408 is done, truck isn't
'03 Ram 1500 QC 4x4 Hemi Off-Road
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posi man
Dodge Dakota
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1/13/2004
21:18:54
| RE: Gear Ratios
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If you have a truck like mine, the hood was changed before you bought it, and the sticker was missing from both the hood, and the glove box, you need to look on the diff itself. There are stamped metal tags on the rear diff of the truck, it will tell you what size it is, and the gear ratio, but will not tell you if you have limited slip. To find out if you do have a LSD jack the back of the truck up, and have a friend hold one of the wheels, while you turn the other one. If they spin the same direction, and your friend cant hold his side from turning, you have a LSD. If the other wheel spins oposite the way you are spinning one of them it is an open diff. To find out the ratio, you can look on the glove box sticker, or if it is missing (like mine) you can call the dodge garage and give them your vin # and they can get you a new one. If your gears have been swapped out by a previous owner (like mine again) then you can jack the ass end of the truck up again, and put a mark on the drive shaft. Have a friend slowly spin one tire while you count how many times the shaft spins. If it spins 3.55 times, you have a 3.55 if it spins 3.92 times, well you get the piont. I was stuck doing this, I was happy to find that my drive shaft spun 4.10 times. Good luck finding out, hope you have stickers, and tags, mine didn't, and it makes it kind of a bitch when you are lowered 7 inches in the back, and floor jacks hit your frame rails when you try to put them under your truck.
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DavidH
Dodge Dakota
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1/14/2004
09:14:30
| RE: Gear Ratios
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Thanks for your help, billyw and posi man, I will check this out this evening and let you know what I find.
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posi man
Dodge Dakota
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1/14/2004
21:05:08
| RE: Gear Ratios
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sweet, hope you find what you wanted to.
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Greggy
Dodge Dakota
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3/27/2004
21:05:42
| RE: Gear Ratios
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Hey Ya'll. Thought that I'd leave a comment or two. I have a 01' Dak witht he 4.7V8. I'm right now redoing my rear diff. I had a rubbing noise coming from it. I pulled the pinion bearing to discovered that I had a bunch of rollers chewed to sh?t. Probably where the noise was coming from. I'm taking the part into the dealership to bring this problem to their attention. If anyone has or had this problem and still have the bearing, bring it in. I have 50,000 miles on that rear end. I had shavings and metal dust in the oil.
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chieftech1
Dodge Dakota
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4/03/2004
12:43:53
| RE: Gear Ratios
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I have a 99' dakota cc w/ 318 and 31x10.50x15's. I want to have it lifted later and was wondering if anyone had any ideas about new gears if I run 33's on the truck. I'm hoping to get more power and better mileage.
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