Engine rpm sweet spot

[Cllowe]

Has anyone found the rpm sweet spot? I have the 3.6 manual, 2 1/2 lift with 33 tires, and stick gears for now. I have been playing around and have found that in 4th gear at 72 mph I am running about 2500 rpm which will get me an average of 19.2 mpg. So far that’s the best since it was stock. Oh yeah I have the afe pro dry air filter. Besides that motor is stock.

Sponsored

 

[jsw872]

i'm still on stock in a willys sport, i run 72mph in 5th gear just at 2k rpm, hardly use 6th, been getting a little over 21mpg

 

[bbroich]

If just cruising on fairly level highway, 2K rpm in 6th seems optimum about 65. Stock Rubi.

 

[Traveller128]

Our 2 door manual likes 2K-2100 for fuel economy. I found with the stock 3.45 gears and 33" tires, that it liked 4th gear at 60-67, 5th gear 68-80. I did back to back testing running 6th gear for a tank on the 80 mph freeway commute, and then reset and did 5th gear for the commute (I cruise at about 78 mph on the GPS). Did that a couple tanks per. I found that 5th gear on the freeway returned the best economy by about 1 MPG (21.5 vs 20.5). On back roads where we ran 60-65 in 4th, 65-70 in 5th, we'd return closer to 23. This was otherwise stock with 33" tires.

With the 4.10s in it now, plus the true-trac, we're seeing 19.5-20.5 commuting and 6th gear is the best gear now. It will do about 21 or a little better on the highways, gravel roads and trails, mixed. The true-trac is the probable cause, the front driveshaft is now spinning (preload in the truetrac won't let it freewheel).

Wind is a killer. Headwind drops the fuel mileage a fair bit, 18 MPG or so on the freeway.

 

[KJKWillys]

i'm still on stock in a willys sport, i run 72mph in 5th gear just at 2k rpm, hardly use 6th, been getting a little over 21mpg

Same here.

 

[Cllowe]

Our 2 door manual likes 2K-2100 for fuel economy. I found with the stock 3.45 gears and 33" tires, that it liked 4th gear at 60-67, 5th gear 68-80. I did back to back testing running 6th gear for a tank on the 80 mph freeway commute, and then reset and did 5th gear for the commute (I cruise at about 78 mph on the GPS). Did that a couple tanks per. I found that 5th gear on the freeway returned the best economy by about 1 MPG (21.5 vs 20.5). On back roads where we ran 60-65 in 4th, 65-70 in 5th, we'd return closer to 23. This was otherwise stock with 33" tires.

With the 4.10s in it now, plus the true-trac, we're seeing 19.5-20.5 commuting and 6th gear is the best gear now. It will do about 21 or a little better on the highways, gravel roads and trails, mixed. The true-trac is the probable cause, the front driveshaft is now spinning (preload in the truetrac won't let it freewheel).

Wind is a killer. Headwind drops the fuel mileage a fair bit, 18 MPG or so on the freeway.

You like the 4.10? I was thinking when I re rear this fall I will do 4.56. I am worried it will be to low though.

 

[Traveller128]

You like the 4.10? I was thinking when I re rear this fall I will do 4.56. I am worried it will be to low though.

It's perfect for the 33" tires, at least for us. Pulls away from a stop with no throttle, crawls around in low range really well, does everything we want including crawling around mountain trails. We like to hike in out of the way places, explore old mining country, go to fire lookouts, basically get way off in the hills. We don't rock crawl, we just explore on sometimes "vague" roads and trails that were trails 100+ years ago. Sometimes it's snow and muck, sometimes major dust and exposed rocks. So far, we've been up over 8000' of elevation, and the gearing and motor are working great for that. Maybe it's different over 10K feet, but the V6/manual/2 door combo is awesome for us.

If we were going to run larger tires like 35's, I think 4.56 would be a good place to be. We really have no intention of going larger, with the extra approx 2" from tires and Rubicon 2 door springs, we aren't scraping anything and it really claws around like a cat with limited slip both ends. Our only plan for the drivetrain at this point, is we'll put a TrueTrac in the rear eventually. Limited slip both ends makes for a very confident feel on the loose dirt/gravel roads and on rocky and slippery steep stuff for us. We run in 4HI a lot on dirt mountain roads, because the loose gravel everywhere is like riding on marbles. Much more confident steering in 4HI.

On the rougher stuff, we turn a knob on the Autolynx and run with the front sway bar disconnected.

Basically, we're enjoying the hell out of the 2 door Jeep, my wife is probably never going to let me sell it.

 

[J.Ferreira]

We have a lot of rolling hilly highways in Colorado and at the beginning of last week I accidentally left my Jeep in 5th gear for the drive with cruise at 70mph. About 2100 rpm ish. That was a fresh tank and my current mileage was sitting at 24mpg when I got to work. I drive 35 miles one way.
Decided to try that for the whole tank and I averaged about 23.5 Which is over the 21.5 average I typically get.
I used to just throw it in 6th for the downhill sections and the flats and then downshift to 4th for the uphills.
But my theory is that 5th has just enough pep to get up the hills without extra throttle input from me and the steady driving is helping my mileage. This week on Monday it said 25!
Time will tell, but I think 5th is the new 6th for me.

Edit: Also stock everything other than minor cosmetic things and personal touches. Drivetrain is intact from the factory sans one oil change and air fliter.

 

[Seer]

Our 2 door manual likes 2K-2100 for fuel economy. I found with the stock 3.45 gears and 33" tires, that it liked 4th gear at 60-67, 5th gear 68-80. I did back to back testing running 6th gear for a tank on the 80 mph freeway commute, and then reset and did 5th gear for the commute (I cruise at about 78 mph on the GPS). Did that a couple tanks per. I found that 5th gear on the freeway returned the best economy by about 1 MPG (21.5 vs 20.5). On back roads where we ran 60-65 in 4th, 65-70 in 5th, we'd return closer to 23. This was otherwise stock with 33" tires.

With the 4.10s in it now, plus the true-trac, we're seeing 19.5-20.5 commuting and 6th gear is the best gear now. It will do about 21 or a little better on the highways, gravel roads and trails, mixed. The true-trac is the probable cause, the front driveshaft is now spinning (preload in the truetrac won't let it freewheel).

Wind is a killer. Headwind drops the fuel mileage a fair bit, 18 MPG or so on the freeway.

Thank you for your post, I was reading several others to make a decision and your setup seems very close to mine! I have 2021 2-door manual sport and I'm never selling this vehicle. I always drove manuals and something is off with the gearing with this one but I love my jeep. It puts a smile on my face every time I drive it.

I'm planning to upgrade to 285/70/r17 (32.7") or 285/75/r17 (33.8") (planning to use my steel wheels which I like so much) do not want to go with bigger tires than these two options.

Other upgrades I have installed (for weight consideration): Eaton true track LSD(rear), ARB classic front steal bumper, AEV real steel bumper with fuel caddy & tire carrier, Steel rock sliders, Tera flex 1.5" performance spacer lift kit.

This is my daily driver and weekend warrior for hiking trips(not doing any crazy rock crawling) I just like to walk those parts. But I drove in deep snow in winters.

would you recommend 4.10 or 4.56 for regearing?

Thanks!

PS1: Dealer fixed the recall for manuals last month
PS2: I'm doing all this slowly due to funds, so it will take me some time to get to regearing but I would like to have the correct size so I can start looking for deals.(Check used ones etc) Not a wealthy individual.

Sponsored