3.73 vs 4.10 gears - fuel economy?

[mtnrgr]

It just doesn't seem to make as much difference as I thought it would. But oh well, it's done. Doesn't have a tach, so I am only going by the ear tach. Eventually going to add another wart to the hood, with a hood tach.

How does the ranger do now with the gear change? When I bought my 94 3.0 5spd new it had 3:45 gears and did ok. In 99 when I had a 6" lift put into it along with 31s, I had 410's put in along with a limited slip..22 years later my ole 3.0 had done wonders.

 

[cbxer55]

Only really drove it from the shop straight to work. Did do a burnout on the way though. LOL!

My tires are maybe 28 inches. Cooper Cobra GTs in 255/60-15. Fronts are 195/70-15.

 

[pjtoledo]

to clarify things a bit the rear axle sensor reads the tone ring, which is attached to the ring gear.
when changing the R & P the tone ring stays the same.

 

[cbxer55]

to clarify things a bit the rear axle sensor reads the tone ring, which is attached to the ring gear.
when changing the R & P the tone ring stays the same.

That's the best explanation yet. Thanks for that. I texted the guy at the shop some of the info here, and his take was that Motive Gear sent me 3.73s instead of 4.10s. I think this will clear up his thinking. He told me I would need to buy a tuner and use that to change it.

Really, the difference in engine rpms isn't super huge. Fuzzy math says it's around 7%. So every 1000 rpms, it should run 70 more. So at any speed where it used to run 3000, it would run around 3210 now. Without a tach, I can't really say. It sounds like it's revving higher, but it's not a huge difference. I'm kinda sorta underwhelmed. I was expecting more. But, onto other things. Found a 98 - 00 front bumper with the driving lights in the lower corners. Going to pick up that and a new fascia with a billet grill. Try and clean up the front end a little. Repaint the hood, weather permitting, which ain't anytime soon from what I can see. Rain, rain and more rain.

 

[sgtsandman]

My experience with that system was there was no change in speed reading or odometer reading. My 1998 Ranger came stock with 3.45 gears in the rear axles. Them mpg was about 21-22 mpg and under powered up until 70 mph on the highway. I changed the rear axle for one with 4.10 gears, the mpg didn't change but the get up and go and general all around performance improved greatly. Granted, the engine as a 2.5 Lima hooked to a 5-speed manual transmission but the 4.10 gearing was a much better match for the engine and the hilly terrain we have around here.

 

[cbxer55]

Going from 3.45s to 4.10 is a much bigger change than 3.73s to 4.10s. Time will tell. As I said, I picked the truck up and drove like 10 miles to work in stop-and-go traffic. Got to get it on a highway, as that is where the rpm rise should be more noticeable. Should be like driving like it used to OD OFF with it on. Or close to it.

 

[sgtsandman]

True but it's the only reference I can give you. For me, it was no change in mpg, speed reading, or odometer reading. I plan on going from 3.73 to 4.56 on the 2011 but the pick location is different and I haven't done it yet. So, it wouldn't be any help for you.

 

[pjtoledo]

going from 3.73 to 4.10, 3.73 multiplied by 1.1 is 4.103
that's about a 10% increase in torque

overdrive is .79, that's about a 20% decrease. or increase if you're downshifting.

 

[DCman]

Yes, 1998 to 2000 Rangers used the ABS sensor on rear axle for speedometer/odometer, it registers AXLE rotations per mile
So ring gear tooth count(or pinion) won't matter, but tire size will matter

Drive shaft speed needs to be converted to rotations per mile using tire size and gearing
3.73 means drive shaft rotates 3.73 times for each 1 time the axle rotates
4.10 would rotate 4.1 times for each 1 rotation of the axle
And then you need to know how far vehicle travels with 1 turn of the axle which varies by diameter of the tire

Good to know that I won't need to correct the speedo if I change gears in the rear end (as long as I stick with the same size tires), so I thank you gentlemen for that information.

However, Ron's definition of what "3.73" and "4.10" mean are incorrect.
Those numbers are Gear Ratios.
ANY ratio is simply a comparison of two numbers.
In the case of "Gear Ratio" it is the comparison of the number of teeth on the ring gear, compared to the number of teeth on the pinion gear.
It is incorrect to think that if your truck has 3.73 gears in the rear end that the driveshaft will turn that many times for every turn of of the axle shaft.
It only means that there are 3.73 teeth on the ring gear for every one tooth on the pinion gear.
Sure, the driveshaft rotation will speed up, or slow down, as you change rear axle gear ratios (everything else remaining constant), but the numbers do not compare directly.
It is simply a comparison of the number of teeth on those gears.

To calculate engine rpm based on road speed and tire height, the formula you use is: road speed (mph), times effective final drive gear ratio, times 336, divided by the height of the tire in inches.
The end result will give you engine rpm.

 

[Blmpkn]

... no... ranger Jesus ron.d is correct

 

[DCman]

No, he's not.
I've proved this to myself several times.

 

[Blmpkn]

 

[RonD]

I think its the same thing if I am reading what was said correctly

example here

So for a 3.10 ratio there are 3.1 teeth on ring gear(driven gear) for every 1 pinion tooth
4 teeth for every 1 tooth on a 4.0 ratio

And so the drive shaft must rotate the pinion gear 3.1 times to get 1 full rotation of the ring gear if ratio is 3.10:1
Or 4 times if its a 4.0:1 ratio
So same thing, tooth ratio and rotation ratio

 

[cbxer55]

going from 3.73 to 4.10, 3.73 multiplied by 1.1 is 4.103
that's about a 10% increase in torque

overdrive is .79, that's about a 20% decrease. or increase if you're downshifting.

Like I said, it's not overwhelming. I felt it more on the highway coming home from work last night, than I do around town. I could tell it was revving a bit more. I don't really care about the gas mileage, my daily round trip to work and back is 13 miles. Sometimes I go the long way and make it 25. LOL

 

[snoranger]

It is incorrect to think that if your truck has 3.73 gears in the rear end that the driveshaft will turn that many times for every turn of of the axle shaft.

But it does... you can jack up a locked rear*, spin the wheels 1 revolution, count the number of turns the driveshaft makes, and it WILL match the gear ratio.

*On an open diff, you only jack up 1 wheel.