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Mike C
Unregistered
3/22/2001
16:32:52
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 Subject: 3.55 or 3.92 gears
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Message:
Can anyone tell me the difference between the two and what it means, or which is better for what?
Mike C.
2001 4X4 CC Silver 4.7L 3.55
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matt
Mechanic
3/23/2001
02:48:10
| RE: 3.55 or 3.92 gears
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3.92 are a taller gear than the 3.55. Which makes them better for towing or turning off road tires, but bad for fuel econ and highway driving.
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KJ
Gen I
3/28/2001
21:05:16
| RE: 3.55 or 3.92 gears
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Message:
The 3.92 gears are good for big tires or normal road driving with a 5-speed or multi-speed automatic. The 3.55 gears are better for regular size tires or interstate type road driving where speed will be 65-70 mph. Higher (numeric) ratios are better for towing and acceleration but work the engine harder at highway speeds and thus use more fuel for that application.
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Bill A
Unregistered
4/02/2001
22:13:10
| RE: 3.55 or 3.92 gears
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Message:
Ok people 3.92 are lower gears. now you are right about the 3.92 better for towing and bigger tires. With axle ratios the bigger the number means lower gears. but be glad you don't have a f-150 some of them come with 3.08 gears. which means they are better for highway not offroad or towing
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matt
Mechanic
4/03/2001
02:23:58
| RE: 3.55 or 3.92 gears
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Message:
No I am dead positive I was correct the taller gear is the 3.92. Give I have eight years in field and a masters in ase cert. The taller gear is the one that takes more drive shaft revs to turn the axle shafts one rev. That makes the ring gear off the 3.92 taller than the 3.55 gear.
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MikeC
GenIII
4/03/2001
12:35:43
| RE: 3.55 or 3.92 gears
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Message:
Seems to make sense anyway, now that I thought of it. Look at a ten-speed bike. The bigger gears are the "lower" ones. My next question would be, is the difference really that substantial?
Thanks,
Mike C
2001 CC SLT 4.7 4X4 3.55 Silver
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Dean
Unregistered
4/07/2001
20:02:53
| RE: 3.55 or 3.92 gears
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Matt you are wrong , the 3.55 are taller. A quik explaination. 3.55 means the driveshaft will turn 3.55 times to 1 at the rear wheel. If you want I have a chart discribing it.
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help me out
Dodge Dakota
JOIN HERE
11/15/2004
10:45:04
| RE: 3.55 or 3.92 gears
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Message:
3.08 is fine as long as you got a big fat v8 pulling.
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DakotaOwner01
Dodge Dakota
JOIN HERE
11/15/2004
14:45:54
| RE: 3.55 or 3.92 gears
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I have the 3.92's in mine gives you more power less speed. I tow stuff and have 31's currently will be 33's in a couple monts.
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.boB
Dodge Dakota
JOIN HERE
11/16/2004
00:07:26
| RE: 3.55 or 3.92 gears
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Message:
A higher numerical gear ratio equates to more torque being applied to the ground. Just like a longer handle on your wrench applies more torque to the nut. Great for city driving, mountains, off roading, towing, etc. In short, doing what a truck was designed to do: Work.
The trade off is higher rpm's, particularly on the highway. At 80mph you'll have a few more rpm's with the 3.92 than a 3.55. That will probably cost you a little at the pump.
OTOH, the lower gear can sometimes keep the engine in the power band at lower speeds, so it becomes a wash. That's a real consideration if you rarely drive more than 60mph. If you have a 5 speed with stock gears, OD is almost useless on.
I used to drive a '95 ram with 5.2/5 speed (great truck). I started out with the stock gears, which I think were about 3.2'ish. At speeds above 70, OD was great. Anything below that, and I was constantly downshifting. If I was running relativly flat ground, but had a really strong head wind, I was downshifting. That Ram was about as aerodynamic as my house.
I later changed gears to 3.55. The truck ran a lot better, had more pep, towed better, but got the exact same mileage. That was probably because it got the engine up where it worked better, and it didn't bog down as much.
As for "taller" vs. "shorter", I agree with matt. The 3.92 is taller because it has a bigger number. It's a slang term, with no real solid automotive definition that I've ever seen. It's just generally accepted that way in my neck of the woods.
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Verde SAR Dog
Dodge Dakota
JOIN HERE
11/17/2004
19:23:19
| RE: 3.55 or 3.92 gears
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Message:
The terminology of "taller/shorter" did come from bicycles. Gearing on bikes is still measured in inches...equivilent to old time big front wheel bikes. Taller front wheels = taller gears = more top speed but more effort ie: higher gears lower numbers (closer to 1:1) for automotive terminology, the numbers for automotive are a ratio of the number of teeth on each gear (or turns ratio) 3.55:1 is actualy a lower gear ratio than 3.90:1 but called a higher or taller gear.
Now that you're all confused... automotive lower gears (higher numbers) mean less top speed but more torque on the road.
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furball69
Dodge Dakota
JOIN HERE
11/19/2004
06:29:41
| RE: 3.55 or 3.92 gears
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Message:
Don't low gears, be it tranny or diff, always mean your engine will rev higher at a given road speed?
ie. low lock 4wd vs. 4 hi
or first(low) vs. third
therefore a 3.90 is a lower gear than a 3.55 because a 3.90 will make your engine rev higher at a given vehicle speed.
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furball69
Dodge Dakota
JOIN HERE
11/19/2004
06:45:45
| RE: 3.55 or 3.92 gears
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As for weather the difference is significant or not I did the math to figure out the rpms at 80mph
at 80mph with 3.55's in OD my rpms are about 2100
with 3.92 gears the rpms would go up to about 2300.
not very substantial if you ask me but it may make the difference between constant downshifting or having to lock out OD altogether if you are towing.
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furball69
Dodge Dakota
JOIN HERE
11/19/2004
06:48:59
| RE: 3.55 or 3.92 gears
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Message:
whether too.
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Brad
Dodge Dakota
JOIN HERE
11/26/2004
02:25:37
| RE: 3.55 or 3.92 gears
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3:92 hands down. The 3:55 in my Dakota suck. Constantly turning overdrive off.
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furball69
Dodge Dakota
JOIN HERE
11/27/2004
03:25:00
| RE: 3.55 or 3.92 gears
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I like the 3.55's because I do a lot of highway driving.
I'd still like the 3.55's for towing or hilly conditions cause I'd rather lock out OD with 3.55s than 3.92s.
I've been shutting off cruise instead of locking out OD; I jsut let the truck slow down on hills and regain the speed once I get over them. unless someone is behind me then I'll kick it down but otherwisse, no... seems to save fuel too.
Would be nice to be able to select 4th gear with the selector though.
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travis f.
Dodge Dakota
JOIN HERE
11/30/2004
13:21:50
| RE: 3.55 or 3.92 gears
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Message:
there is a complet rear end on ebay right now with 3.92 if any one is interested
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=7937969479
it's going cheap right now
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