02 S-10 gearing question.
 

Here’s one for the gurus. I looked up the truck and google lied. Said it had 3:73 gears but the manual says 4:10. At 65 it’s at least 2500 rpm (I will edit tomorrow with actual rpms). I would like to drop them lower so here’s the situation:
I have a GearVendors unit in the 93 3500 truck and it drops rpms by 500. I cut the driveshaft and installed it myself. Would it benefit me to put it in the S-10 or should I leave it alone and sell the unit? Pretty sure it would sell between 1500-2000 which i could use towards gas.
I just got the truck and my plans are to go camping. Some trips will be over 1000 miles round trip. Right now I avg 25 and fill up every 300 miles or so (there’s something wrong with the sending unit. PO said it will run out before empty). I will carry an extra 30 gallons in the back and use a pump to fill when needed.
What are y’all’s thoughts?

"Don't be evil' is water under the bridge.

Even DuckDuckGo is looking sketchy, being powered by Bing, which is down the AI rabbit-hole.
I hear good thinggs about Brave Search, and then there is StartPage.

Why support those that don't even pretend to not be evil? And where is Larry Page?

I say be evil.
Just don't hurt too many people that don't deserve it.

GM gear ratios are about 9% between ratios. So 18% is closest to 3.42 for your 7.5” rear end. That is a big jump, I played with gear ratios when I was running Geo Metros several years ago. I don’t know if 3:73 will be enough to be worth the trouble, that is entirely up to you. The 3:42 set might be 4th gear into a head wind with a 2.2. The V6 s10 probably has an 8.5” diff with 3:73 or 3:42. Driveshaft might be a different length with the 8.5”.

I dunno. Is that evil or righteous? :confused;

yes. it IS a lot of trouble/time to put one in. i’m leaning towards selling it.

I wouldn't bother with a gear vender unit.
Standard gm gear ratios should be fine.

'2500-rpm @ 65'
 

For the OEM truck, GM may have already 'optimized' the gearing, considering passing acceleration, hill climbing, full load, towing, etc..
To arbitrarily change it, you'd be completely shooting in the dark.
My CRX has three overdrive gears and 'ANY' headwind, road grade, passing maneuver, etc. requires a downshift to, as low as 3rd-gear, just to maintain a constant speed.
At Bonneville, I could never take it out of 3rd, as , if I did, the engine would completely come out of it's torque curve and fall on it's face. I'd go from 97.386-mph top speed, to 89.61-mph.
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I recommend that you exhaust all available avenues of research to see what other S-10 owners have experimented with, and all the outcomes.

Although adding an external overdrive should move the engine to a more efficient RPM/load, you're also sending power through a lossy extra set of reduction gears, which probably eats 2-4% of the total fuel economy. You lose part of what you gain.

True. Although I couldn’t notice any reasonable gains in mileage in the other truck it at least brought rpms down enough to reduce strain on the engine.

RPMs
 

Many decades ago, HOT ROD Magazine did a project with Ford Ranchero, which included adding a Gear Vendors OD unit. I may have discussed it in my 'lectures.'
I don't have that data at hand, but my memory is that, it was well worth the trouble.
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Back in 1976, messengers reported that a 28% overdrive would produce a 19% improvement in fuel economy.
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I swapped out a 3-speed 1:1 transmission and 4:56 rear end, for a 4-speed OD trans and 3.50:1 axle in my grandad's '61 DODGE D-100, which along with steel radials and some aero brought the indicated 55-mph top speed & 11.0-mpg, up to an indicated 91-mph top speed, and 21.5-mpg.
It was just a leap of faith, but it worked out.
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We can't have any 'a priori' knowledge of what gearing would do for you.
If you were to do any significant 'streamlining' to the Chevy, the PhDs' would tell you that taller gearing would be mandatory.

Your making it hard to decide what to do.....

Throw the I Ching?

HOT ROD's Gear Vendors experience
 

From: HOT ROD Magazine, December, 2008, pages 102-105, by Christopher Campbell.
* Their project truck was a 1967 Ford Ranchero GT.
* With C4, 3-speed automatic, pre-lockup trans.
* OEM, @ 65-mph = 13.0-mpg.
* With street-rod mods, 17.0-mpg @ 65-mph.
* Adding electronically-shifted 0.78:1 overdrive = average 19.5-mpg. As high as 20-mpg, once.
* Average 14.7% mpg improvement.

some CAR and DRIVER S-10 Road Test Data
 

I had a Car and Driver article for the 1994 model year GMC Sonoma SLS ( a mechanical clone of the Chevy S-10 Super Sport, regular cab, with 4.3-liter V-6, 195-bhp @ 4500 rpm, 5500 rpm redline, and GM 4L60-E, 4-speed overdrive automatic trans, with 3.42:1 ring & pinion, P 215/ 65 HR-15 tires.
--------------------------------------------------------------------------------------* In 4th-gear, the truck is geared for 140.4-mph @ rated power.
* 2,500-rpm, in 4th = 78-mph.
* The truck achieves a governed top speed of 112-mph, in 3rd-gear, @ 5150-rpm.
* In 4th-gear, the truck holds 112-mph, @ 3,600- rpm ( 80% of rated power, and peak torque.
* 4th-gear = 31.2-mph / 1,000 rpm @ engine.
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* Both a Borg-Warner T5 manual five-speed overdrive transmission, and New Venture Gear manual five-speed were available, depending on engine package.
I don't have any data for the NVG transmission.
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As of 1975, Borg-Warner had engineered a 5-speed 1:1 output shaft unit, which would be used in conjunction with a lower numerical ring-and pinion to achieve the desired 'overdrive' final drive ratio, but without the 2% attendant mechanical loss of a typical OD transmission. Not used by GM as of 2004, when the S-10 went out of production.