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22:06:28 - 05/02/2024
Off-Road
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jeff kreman
GenIII
11/18/2002
22:39:45
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 Subject: Gears, explain this to me?
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Can someone please help me out here. I am trying to figure out the difference in gear ratio, and in lamen terms. Like whats the difference between say 4.56 and 3.55, or 3.90? I do know a little about ratio of driveshaft, but does that have anything to do with this? Also, I have 31" tires, and stock gears. I want to go with 33" tires in the future, and a powertrax no slip, what kind of gears would I realistically need? Thanks for any help.
Run your fingers over my truck, and I'll run over your fingers with my truck!
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Hawkeye
*GenIII*
11/19/2002
21:59:03
| RE: Gears, explain this to me?
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The lower the number, the higher the gear is. The higher the number, the lower the gear is. For larger tires, or heavy pulling, you want low gears. For more speed and better mileage, you want higher gears.
Example. If you took two truck set up identical to each other in every way, and one had 3.55 gears, and the other had 4.10's, then drove them side by side, and had each running at 2000 rpms, the one with the 3.55 gears will be traveling at a higher mph than the on with the 4.10's.
A 3.55 ring and pinion means that drive shaft will make 3.55 revolutions, to every 1 revolution of the rear axle, etc.
I have run 3.55's and 33x12.50 tires on all my trucks I have ever owned. No problems at all. 3.73 or lower would be optimal to me, but not lower than 4.10's. You will start eating up gas pretty good then, and not get that much more of a payoff in performance, especially on road. For 35's, anything from 3.90 to 4.56 is good. You have to also take into consideration what engine you have. A V6 will require a lower gear to pull the same load a V8 will for example. Also have to take into consideration what gears are in your transmision. There are charts to be found everywhere staing what the optimal gear selection would be for what tire, and gives the speed, rpm's, etc, but I dont like those charts. They are very vague in that they dont take into account the different gear ratios in the transmission from one brand, make and model to the next, or even among the same brand. My wife has a 99 4x4 Durango. I have a 2000 4x4 Dakota. They have two different tranny's. The gear ratios in her tranny are much higher than mine. I am running 3.55 gears in my axles with 33 inch tires and no problem. She has 3.55 gears and 31's. I fI went to 33's on her truck, it would not handle the bigger tires nearly as easy as mine with the same ring and pinion, because her tranny gear ratios are different. Mine are lower overall. I'll stop now so as to not get this anymore confusing. ;-)
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blackbeauty
GenIII
4/05/2003
05:11:36
| RE: Gears, explain this to me?
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Message:
Simple enough,
I have a 4.7L V8 with 3.92. If you have 3.55's, with a V6 I would want a 3.92. If you do any off-roading when you want power and axle protection, you will want 3.92's also. Basically, you can have a wussy 4 cylinder engine and huge gears, you'll do just fine, rather that the V8 with 3.55 or lower gears that will struggle. It all depends on your needs and usage. Do you want gas mileage or performance on or off road?
clean&shiny is good, mud&dirt is better
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AHersh
GenIII
4/17/2003
13:38:15
|  RE: Gears, explain this to me?
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Message:
With an I4, gears are a good idea for 33's. Something in the high three's should do the job just fine, but what are your plans? Is there any serious off-roading in the future?
My brother used to have an '86 Yota with the I4 and had 33" Mickey Thompsons. I turfed the truck hard in Gorman (CA - Home) and it was really begging for power. When I dropped gears for juice, there wasn't anything there. Also, without gears, the truck had a hard time on long grades and got pretty hot.
Tall gears (higher number) give the engine more leverage. With the I4, I would consider 3.93s. You are going to lose some top-end, but will need the low-end grunt they are going to give you. Depending on where you purchase the gears, somebody should be able to answer you questions. Like Hawkeye said, there are charts to help you match the current set-up.
1997 CC 4X4, 5.2L Manual
Dynomax UltraFlow, K&N Drop-in, Mobil1 in Motor & Gear Boxes, Rhino Lining
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AHersh
GenIII
4/19/2003
14:48:49
| RE: Gears, explain this to me?
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I was just looking at tires and came across the following link:
http://www.4wheelparts.com/Tirel_Gear_Ratio.asp
It provides a chart for matching gears to tire size.
1997 CC 4X4, 5.2L Manual
Dynomax UltraFlow, K&N Drop-in, MOOG Ball Joints, Bosch Platinum Plugs, Mobil1 in Motor & Gear Boxes, Rhino Lining
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blackbeauty
GenIII
5/01/2003
04:14:11
| RE: Gears, explain this to me?
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Message:
Those gears vs. Tire size charts are only good for matching original engine ratios and speedo accuracy. If you want to put more turning power to your tires while crawling over rocks then you want taller gears (higher gear ratio number) than what the chart says. Keep in mind, you can put on 44 inch swampers on an 8.25 Chrysler rear axle and break your axle shafts real quick. Go to a 4x4 shop near you. I'm sure they are eager to talk about your truck with you. Don't be intimidated.
clean&shiny is good, mud&dirt is better
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