Gear change.....lower?????
 

Hello everyone.

I am getting ready for the gear swap from 3:73 to 3:45. I was talking with some "gearheads" at work the other day and they seem to think I will do better with 4:10's rather than 3:45's. I told them it may be better in town but I spend most of my time on the highway. They said "oh you'd be surprised."

I still think 3;45's are the way to go, but in an effort to try and learn something here, can someone explain to me why these guys think they are right with the 4:10's? I would think my poor little 2.3l would be turning way to many rpm's at 60 mph with such a low gear.

Thanks for trying to teach "non-mechanical" me something.

I like my 3.45 and my mileage is great with the .80 overdrive 5 speed. Maybe your friends just don't get 30+ mpg in a pickup truck. If I wanted a 4.10 I guess I could downshift two gears.

regards
Mech

Well, sure they'd think that 4.10:1 would be better. You'd practically give yourself whiplash whenever you'd accelerate from a dead stop, and your in-city fuel economy would improve a bit. Wouldn't do your highway fuel economy any good, though.

If you reach for advice outside the ecomodder community you aren't likely to receive the best advice. Tuning for max fuel economy is an extremely small niche relative to the power and speed group.

That being said, it's well documented here on EM that lower RPM at a certain speed = better fuel economy. For highway cruising you will want the tallest gearing that will work in your application.

I had someone tell me that a cold-air intake would improve my mileage. When I tried explaining a warm-air intake he essentially called me a heretic.

higher rpms = faster pulse
 

That is true for cruising, but the only difference with P&G is the pulse. Compared to a DX, my EX has higher rpm's, but also a faster pulse that results in a greater glide ratio.

I have noticed this in my Festiva. It doesn't do well at all at highway speeds, but low speed pulse and glide on back roads, I feel it's almost as good as any option.

They will also tell you you need a 9" rear end. Ignore them.

In my truck I can always choose a lower gear for the pulse.

3.73 to a 3.45 is not much difference, about 10% lower cruising RPM.

97 Ranger transmission ratios (Mazda transmission):
1st
2.47
2nd
1.87
3rd
1.47
4th
1.00
5th
.75

Basically at 3.00 rear end and a 4.00 rear end would be the same as 4th gear with the 3.00 and 5th with the 4.00.

I guess it takes too much effort for your friends to downshift if they want a higher overall final drive ratio. Personally I like the lower engine RPM on the highway, and if I am climbing a hill that I can't climb in 5th then just go down to 4th or 3rd.

Meanwhile I have a overall final drive ratio they do not have and they are paying for it every day they drive.

When I bought my Ranger I knew the transmission code for the rear axle and much to my delight it was the 3.45. The owners manual says to never jack up the rear end using a floor jack and the center of the rear axle. I wonder how many ranger rear axles have been ruined by those who never read that information.

regards
Mech

I agree with all of you. I thought maybe (by some weird twist of mechanics), if there was something to what they said I could learn something. I guess what I did learn was not to listen to listen to guys who like to go faster than farther. :)

Here. Have a picture. Lower rpm is better for mpg.
http://ecomodder.com/forum/attachmen...1&d=1400613088
Edit for better version.

that graph feels like it has too many axis(axii?).

anyways, i have spent a lot of time with a 92 2.3/5 speed/2WD/3.45 ranger....

it pulls itself along in 5th as low as 40MPH without too much complaint from the engine and will accelerate(slowly) as long as you're not going up too much of an angle. sitting at 55, i feel like i could grab an extra gear if there were one, i want to say the engine is sitting around 2000RPM at that point. at 70, it's super buzzy and definitely could use a 6th gear. i wouldn't want to go with numerically higher gearing, or else you'll be moving yourself even further away from the torque peak.

On my 97 Ranger.

rear tire diameter 24.75 inches
multiply by PI 3.1416
77.75 inches per revolution
divide by 12 to get feet
6.479 feet
divide 1 mile by 6.479 feet
815 revolutions per mile

.75 over drive 5th gear times the rear axle ratio
2.5875 overall final drive ratio in 5th.

815 revs per mile X 2.5875 revs of the engine per rev of the rear wheel.

2109 RPM at 60 MPH.

regards
Mech

Here's a version that may help.
http://ecomodder.com/forum/attachmen...1&d=1400613088

much better, having the colors similar/combined confused me for a few seconds and i look at charts/graphs for probably a solid hour a day. i do have a touch of color seperation/blindness though.

My '86 MG half-ton has a 3.08 and the "granny low" 4spd. When I drove it everyday it would do ~16-18mpg highway and ONCE it got 30 in-town. That once was with a nearly empty tank (and I knew it) driving TO the gas pump about 15mi away. I did the speed limit in town always but was never in a hurry to get up to speed, highway I kept it @60.
Wish it had OverDrive!

The 9" probably isn't the right choice for what the gearheads are doing either...

Picking up the 3:45 in about a week. He says he also has a 3:27??? Never heard of that one. Probably too high a gear for the little stock 4 cyl. But in the interest of learning (and I think I already know the answer), is the 3:27 too tall? I'm staying with the 3:45 anyhow because I still drive in town sometimes and with something that tall (3:27) I'm pretty sure the gains on the highway would be lost in town.

You have a manual. If it's too tall, you can always run a gear lower.