Gear ratio and mph

[joeweger]

I changed my rear end from 3.73 gears to 3.45 what is the difference in speed?

 

[sgtsandman]

It depends on the year of the truck. 1998 and up, it won’t make a difference.

Why would you put a 3.45:1 gear ratio in your truck? That gearing usually hurts fuel economy and turns the Ranger into a dog unless you put a different engine in it to compensate.

I went from 3.45:1 to 4.10:1 and the mpg never changed but it’s get up and go improved by a huge amount.

 

[Curious Hound]

This should help.

Gear Ratio & RPM Guide For Larger Tires - The Ranger Station

This Gear Ratio & RPM Guide will enable you to see how many RPM's your engine will turn based on gear ratio and tire size.

www.therangerstation.com

 

[scotts90ranger]

If you look what color or tooth count speedo gear you have now and get one less it'll probably be pretty close...

 

[RonD]

3.45 ratio will have a higher top speed at the same RPM in a specific gear, than 3.73

i.e. a 3.45 with engine at 2,000rpms will be travelling at 70mph in Overdrive
A 3.73 at 2,000rpm would be travelling at 65mph in overdrive
Assuming same size tires

3.45 at 3,000rpm would be travelling at 100mph in overdrive
3.73 at 3,000rpm would be travelling at 95mph in overdrive

But as said a 4.10 ratio would get you to 70mph or 100mph much faster, but at higher RPMs

In a Ranger lower ratios were for better MPG, i.e. lower rpms on the highway when cruising
Cars with V8's used lower ratios for top speeds

 

[joeweger]

I changed my rear end from 3.73 gears to 3.45 what is the difference in speed?

 

[racsan]

“technically “ it would go faster, but be slower getting to a given speed. (0-60) I say technically because if you have a small engine like a 2.3 lima it might not have the horsepower to overcome the increased resistance to get to 90. I went from 3.45 to 4.10 and rpms are higher at certain speeds but it gets to 60 quicker and has much more bottom end pull. 85 is all it has overall, it just runs out of tourque at a certain rpm and wont go any faster. With 3.45’s it probably would max out at a similar speed but take longer to get there. (wind resistance).I never drove it hard with the 3.45’s, the axle swap was one of the first things I did. 3.73 is probably the best balance of power vs economy, I just always wanted to try 4.10’s with a 2.3 so thats what I went with.

 

[pjtoledo]

mathematically your speedometer is now off by about 8% unless your Ranger uses the rear axle tone ring for speed,,then it won't make a difference.
you will be going 8% faster than is indicated.

in reality speedometers usually read faster than you are actually going, so the difference will not be exactly 8%
get a GPS or navigation app that shows speed to find out exactly

you will not like long inclines with the 3.45 gears.

 

[sgtsandman]

“technically “ it would go faster, but be slower getting to a given speed. (0-60) I say technically because if you have a small engine like a 2.3 lima it might not have the horsepower to overcome the increased resistance to get to 90. I went from 3.45 to 4.10 and rpms are higher at certain speeds but it gets to 60 quicker and has much more bottom end pull. 85 is all it has overall, it just runs out of tourque at a certain rpm and wont go any faster. With 3.45’s it probably would max out at a similar speed but take longer to get there. (wind resistance).I never drove it hard with the 3.45’s, the axle swap was one of the first things I did. 3.73 is probably the best balance of power vs economy, I just always wanted to try 4.10’s with a 2.3 so thats what I went with.

My ‘98 had the 2.5 Lima and struggled to get out of it’s own way until about 70 mph. Then it started to do better. On paper, I suppose the 3.45 axle it came with made sense but in reality, it was a dog and fuel mileage suffered instead of improved since the engine was being over worked. Ford should have stopped at 3.73 with an I-4 equipped Ranger.

 

[scotts90ranger]

In the olden days they put even lower gears in, my '90 came with 3.08 gears but 190 70 14 tires... it didn't do too bad on the highway and the gas mileage was great when the engine was healthy...

 

[sgtsandman]

In the olden days they put even lower gears in, my '90 came with 3.08 gears but 190 70 14 tires... it didn't do too bad on the highway and the gas mileage was great when the engine was healthy...

Terrain makes a difference. The ‘98 had 225/70R14 tires. So, a little bit taller, I think. The truck was supposed to get something like 27 or 28 mpg. It never saw better than 22 before and after the axle swap. Pretty much what any other small truck I had ever driven got in the past. One was a Nissan truck with a four banger and a Chevy S10. I’m pretty sure both of those had a 4.10 in the rear axle.

 

[lil_Blue_Ford]

IMHO, 3.73 gears are about ideal for a stock RBV. My first Ranger had them and there was times where I would have preferred a little deeper gear (4.10), but it got good fuel economy (right up until the ethanol gas) and did everything I needed it to. That is my blue 2000, and I had it up to 110 once. My red 92 also has 3.73 and with a shift kit in the auto trans and a 4.0, it was pretty solid. My green 2000 had 4.10 gears and it was a bit of a dog actually compared to the 92, but I didn’t do a shift kit to the auto trans. I swapped the green 00 to a 5.0 and changed to 3.73 gears but it isn’t complete yet so I don’t have road performance.

 

[sgtsandman]

IMHO, 3.73 gears are about ideal for a stock RBV. My first Ranger had them and there was times where I would have preferred a little deeper gear (4.10), but it got good fuel economy (right up until the ethanol gas) and did everything I needed it to. That is my blue 2000, and I had it up to 110 once. My red 92 also has 3.73 and with a shift kit in the auto trans and a 4.0, it was pretty solid. My green 2000 had 4.10 gears and it was a bit of a dog actually compared to the 92, but I didn’t do a shift kit to the auto trans. I swapped the green 00 to a 5.0 and changed to 3.73 gears but it isn’t complete yet so I don’t have road performance.

The 3.73 in the 2011 was ok as long as it was not carrying much and had the stock tires. Not so much now with the gear in the bed and the 31’s.

The 2019 with a proper powerplant in it runs just fine with the 3.73s. The extra 63 horsepower makes a difference.

 

[cbxer55]

I changed my 98 from 3.73 to 4..10 a few years ago. I love it.

I didn't notice any speedometer or odometer reading change when I first did it. A few months ago, I put on shorter tires. 14's instead of 15's. Rear tires are now about a half inch shorter than the tires that were on it previously. 25.6 rather than 26 even. Speedo is off around 10% now. I pick up almost a tenth of a mile extra every mile. But, I don't care. It works for me. The old Cragar rims are worth it.

 

[cbxer55]

On a similar tack, my 04 Lightning has a tone ring on the axle. I was told by a guy on LightningRodder that it is used exclusively for the ABS system. When I changed the gear ration on it from 3.73 to 4.10, my speedo is now off 10%. Without touching the tires. I googled it, and it appears to be correct. Maybe Ron D. can straighten me out on this.

On Wednesday, I put a set of 17 inch rims on it. Race Stars. 17 x 11.5 rear, 17 x 4.5 front. Fronts are Mickey Thompson 28 x 6 x 17. Rears are M & H Race Master 390/40-17. They are about one inch taller than the old tires. So, will have to see what affect this has on it. when Mother Nature allows it. Maybe tomorrow.