"Gear" heads please check in

95_togo · May 21, 2004

called a local shop and asked how i can improve gas mileage by changing gears (with gas $2.20 a gallon - you can guess why) i don't know what's in the truck now, but they told me that for better gas mileage and to keep the RPMs down, i need to increase the number (i.e. go from 3.73 to 4.10) does this sound right?

brief exp. of truck

95 1500 x-cab 5",7" drop 245/45-17 tires (total tire height about 20")

the lower gear, higher gear means nothing to me at this point, so i might need a little education on that as well.

so - if i did have 3.73, would i be better off putting in 4.10 or 2.xx?

keep in mind this truck is just for the purpose of driving around town and back and forth to work (50 miles one way) for all the true gear heads - my "raceable" cars are in the garage! so thos needs not be something to take into consideration of putting in 4.10 just for acceleration.

so - let's hear it!!!!

TX-TahoeLtd · May 21, 2004

I believe if you have 3.73 gears now, then lower gears would be 4.10 and higher gears would be like 3.07 or 2.92.

The way I understand it is if you mark a spot on your tire. The gear ratio is how many times it takes the driveshaft to go around before your tire makes one complete rotation.

So, if the shaft spins around 3 and 3/4 turns before you get back to your starting point on the truck, then you've 3.73 gears. This may all be off some if the overall rolling distance of your tire has changed due to your wheel/tire configuration.

That's the way I understand it....so don't shoot me if it's off.

I'll let the experts chime in now...cause I'm certainly not one.

May 21, 2004

4.10 gears are power gears. 3.73 gears are mostly for trucks with light otwing packages. If you want more mileage go from the 3.73 to the 3.4X gear. Don't expect to get much more. Check the stickers on new vehicles they generally give 1 mpg increase to trucks without towing packages.

Doesn't sound like much. If you're getting 15 mpg, then 1 mpg more is about 7 percent increase. Seven percent of a tank full in my Yukon is $3.50. Fillup once a week and you save $182/yr. How much are the new gears (installed). It may take a couple years to pay for themselves.

redvett · May 21, 2004

A 3:42 gear is the next gear up. Figure how much the conversion costs say $600 and how many miles you drive a year and how long it will take to get a payoff. In my estimation its not worth it. Spend the money on a good tuneup and save the rest.

95_togo · May 21, 2004

A 3:42 gear is the next gear up. Figure how much the conversion costs say $600 and how many miles you drive a year and how long it will take to get a payoff. In my estimation its not worth it. Spend the money on a good tuneup and save the rest.

they told me to go to 4.10 - (if in fact i do have 3.73s which is still TBD)

the cost to replace the gears was $800 - what about going to yet oen more - what is the next step past 3.42?

and does anyone think that replacing the entire rear end myself would be more cost effective than having them just change gears?

99-2door · May 21, 2004

If you replace 3.73s with 4.10s you are gonna get worse gas mileage, especially if you do much highway driving.

As someone posted earlier, the higher the gear numerically the lower the gear ratio. That means that your output shaft on the tranny turns 4.10 times for every revolution of the tire, opposed to the original 3.73 time to turn the wheel once. That means higher RPMs for the same speed.

I bet your truck has 3.42s to start with, most 2wd 95s do. Check the RPO codes in the glovebox.

GT4= 3.73

GU6= 3.42

GU4= 3.08

You either misunderstood the shop or they are trying to rip you off. Believe me, you do not want 4.10 gears and 20" tires.

There are more factors to consider than just gearing too. What engine does your truck have? transmission?

IMO 3.42s are the best all around gear set for the 88-98 2wds

3.08s and it is a dog that drinks gas because your foot is in the throttle all the time, 3.73s and 4.10s it is revved up all the time drinking gas unneccessarily.

Go to Smokemup.com , there is a gear calculator there that will help you out.

redvett · May 21, 2004

Gearing the truck too high will cause the engine to be out of the power band. The result the engine will be working harder and worse mileage. Change the tires up one size larger in height and recalibrate speed senser for larger tires will help and be cheaper.

Cop_Dodger · May 21, 2004

It really depends on your driving habits and driving conditions. A lower gear ration (like a 4.10) will give you better gas milage if you drive mostly city. The reson behind this is your 7000# truck is now easier to move from a stop, but you will loose milage on the highway due to the higher rpm's in overdrive. If you do alot of interstate driving stick with the gears you have.

Shotgun · May 21, 2004

Your current tire diameter is 25.68.Your truck probably came with 235-75R-16's and the diameter of these tires are 30.46" Your definatly need taller gears since you dropped 5" on your tire diameter. So, with your smaller tires you are currently running an actual gear ratio of 4.42. You would need to go to at least a 3.42 ratio to get you back to around an actual 3.73 ratio. I think you need to go with like a 3.31 ratio if you never plan on towing heavy loads and just use your truck for cruising.Hope this helps.

drumset5994 · December 26, 2005

I've got 3.08's ...

1st gear and 2nd gear are fast as hell...this truck moves

Then after that its all over.

Ben · December 26, 2005

Yup, depends on many things. One size fits all does not apply here....

First, the HOW2's of gearing and "power" (torque, HP, etc).

Mulitiplication is what gears do. 1:1 is not mulitiplication, or it can mulitiply the power "up" or "down".

A 3.73 diff ratio has the drive shaft turn 3.73 times for each axle turn. So it mulitiplies the drive shaft power by 3.73 times. 100 ft/lbs of torque will translate to 373 ft/lbs, minus losses, of torque at the axle.

Ditto 4.1's. 100 ft/lbs in and 411 ft/lbs out.

BUT, there is a price to pay....some times.

More turns by the engine for the same axle rev says more fuel used, generally.

Generally meaning in reference to those who have mentioned engine curve/torque band/etc. Driver style, loading and terrain also affects this.

Take my 1980 Silverado C10. Had 2.08 diff ratio or something like that. After spec'ing out a "built" engine (stainless valves, ported, flowed, matched, polished, CC'd, cam, etc head), "built" tranny (HD clutches, shift kits, reprogramed valve body, etc) it didn't get very good MPG and not the performance I wanted/expected.

Found that dad had ordered that truck with the "economy" diff ratio.

Went back to the performance shop and had them install 3.73's. Daughter #2 found out that her daily could take and beat Mustangs out on the boulevard. MPG went up 2-3 MPG too. Nothing else was changed, just the diff gears from 2.X to 3.73's (33x12.5R15LT C tires).

So it "depends" on many factors and not just your truck. How you drive, what you haul/tow and where you drive matters. Toss in tire size too.