Optimal tire size for 4.56s gears and 42RLE?

I'd pick the ratio that lets me cruise on the flat Interstate at 65mph and 2000rpm... in top gear. I can always down shift, but cruising over 2000rpm kills gas mileage.

I have a TJR, 33s, 4.10s. I wish I had 3.73s.

On another note, my '87 YJ, 33s, 3.07s, got 25mpg in 4th.... average over 2000 miles from Yellowknife, NT to Denver, CO. cruising over 75mph. First trip with the TJR..... I was searching for gas stations. Getting under 20mpg.

Another cute aside, I got a ticket on a Wyoming Interstate for doing 78mph in a 75mph zone. The cop was on the other side of the Interstate, took him 10 minutes to turn around and catch me.
 
billiebob said:
I'd pick the ratio that lets me cruise on the flat Interstate at 65mph and 2000rpm... in top gear. I can always down shift, but cruising over 2000rpm kills gas mileage.

I have a TJR, 33s, 4.10s. I wish I had 3.73s.

On another note, my '87 YJ, 33s, 3.07s, got 25mpg in 4th.... average over 2000 miles from Yellowknife, NT to Denver, CO. cruising over 75mph. First trip with the TJR..... I was searching for gas stations. Getting under 20mpg.

Another cute aside, I got a ticket on a Wyoming Interstate for doing 78mph in a 75mph zone. The cop was on the other side of the Interstate, took him 10 minutes to turn around and catch me.
Click to expand...
He was really bored!
 
  • Like
Reactions: 2006TJ1
My neighbours Tundra has a 5 speed, double OD.

The Audi A8 years ago with an 8 speed, triple OD hits top speed 156mph? in 5th, which is direct. It loses speed with every shift after 5th. If you want performance, gear for top speed in DIRECT which is the most efficient "gear" to transfer power to the wheels, and use the less efficient OD to reduce rpms, noise, wear and increase gas mileage.

In the 1970s, during the first OPEC gas crisis, OD became an industry standard to increase gas mileage. OD should never be considered for performance. GEAR for the direct ratio.

In the 1970s, the CJ5 came with a 2.72 rear end.... my 1975 Trans Am had a 2.56 ratio. History will tell what and why. Most forums today are dominated by one point of view and those zealots preaching will crucify anyone who disagrees.
 
Last edited:
Keep in mind the OPs question....

"Can anyone tell me the optimal tire size for running this setup on an 06' X with 4.0 liter and 42RLE automatic trans. *Note this is a daily driver as well."

He wants advice for a daily driver, not a weekend beach buggy or a trailered rock crawler.
 
billiebob said:
Keep in mind the OPs question....

"Can anyone tell me the optimal tire size for running this setup on an 06' X with 4.0 liter and 42RLE automatic trans. *Note this is a daily driver as well."

He wants advice for a daily driver, not a weekend beach buggy or a trailered rock crawler.
Click to expand...
I daily drive an '06 X, 42RLE trans, 4.88 gears, 33s. It's perfect. Gas mileage sucks.

I also have an '06 Sport, 42RLE, 3.73 stock gears, 30" tires. Not as peppy as the 4.88 gears. Gas mileage is only better by 1-2 mpg.
 
billiebob said:
Keep in mind the OPs question....

"Can anyone tell me the optimal tire size for running this setup on an 06' X with 4.0 liter and 42RLE automatic trans. *Note this is a daily driver as well."

He wants advice for a daily driver, not a weekend beach buggy or a trailered rock crawler.
Click to expand...
How many times do you want me to answer it?
 
billiebob said:
My neighbours Tundra has a 5 speed, double OD.

The Audi A8 years ago with an 8 speed, triple OD hits top speed 156mph? in 5th, which is direct. It loses speed with every shift after 5th. If you want performance, gear for top speed in DIRECT which is the most efficient "gear" to transfer power to the wheels, and use the less efficient OD to reduce rpms, noise, wear and increase gas mileage.

In the 1970s, during the first OPEC gas crisis, OD became an industry standard to increase gas mileage. OD should never be considered for performance. GEAR for the direct ratio.

In the 1970s, the CJ5 came with a 2.72 rear end.... my 1975 Trans Am had a 2.56 ratio. History will tell what and why. Most forums today are dominated by one point of view and those zealots preaching will crucify anyone who disagrees.
Click to expand...
No, most forums are not dominated by one point of view. I see gear discussions daily. I have seen at least 20 shops recommend 3.73's and 4.10's with 37's as being perfect and several agreeing with them saying their rigs on 37's will even accelerate up hills in OD.

You listed several vehicles that have almost nothing in common with the TJ so how about my truck? 3.73, and it pulls a 14,000 lb load up hills at 65 in OD that none of my TJ's will go up empty with stock gearing without downshifting out of OD. But, how is any of that relevant? Should we use that example to all go back to 3.73 or toss it as non applicable?

What would happen to your neighbor's Tundra if he tossed on a set of 35's? Is he going to gear it higher or lower or leave it alone? Same question for the Audi, when is the last time you saw one on much larger tires? Can you even put 2" larger tires on that car without cutting the wheel wells?

Have you ever driven a CJ-5 with the manual trans and 35's and 2.72's? If you have, tell me one good thing about that set up.

Last question for you. Have you driven for any length of time a TJ with the 42RLE, the stock gears, and larger tires?
 
That Jeep looks good....I wouldn’t change it if it’s smooth.
 
Top Bottom
Back