New gearing???

[Wheelin98TJ]

Man I don't know how else to explain it to you, you're not getting it and I don't have the crayons to explain it another way.

If it works for you that's great, have fun. There's a reason 99% of performance lifted vehicles match the gearing the way they do. You keep bring up 85MPH, but that's simple not what the majority of Jeep owners are doing with their vehicles.

I'm done explaining it, you want to run 3.55's and 40's on your Jeep have fun, someone gotta keep the transmission rebuilders in business. I know I know you've got a whole 25K on your jeep and haven't burnt the transmission up yet...that's great.

Just give up now. I've been down this road with him several times.

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[CJ5w4wdSmokyOnMyTail]

That's exactly the point, it all depends on what you want out of the vehicle. I've worked on moon buggies, 4cy crawlers, big block rock bouncers, all the way to KOH and Baja trucks, and there is no 1 answer fits everything. I had a 80HP Samurai-based rock crawler on 40's that could idle up a vertical wall thanks to its gearing, but had a top speed of about 30mph, Had I had the factory gearing in that buggy I would be putting in a new clutch after every weekend trip. Worked on 1000HP 1ton built rigs running 44's on 4.10's that had been in service for years, no problems. There's a reason the old SM465 transmissions with the granny first gear were such monsters and everyone loved them.

Lower (numerically higher gears) reduce stress on the transmission in exchange for engine RPMs. The exact same Jeep on 40's will have less strain on it's transmission with 5.13's vs 4.10's, but it will run at a higher RPM with the exact same speed/transmission gear.

In your situation, pulling a trailer up a steep dirt hill, what would be BEST for the Jeep would be to drop it into 4lo and sit at about 2K all the way up the hill, that would put the least amount of stress on the Jeep, resulting in the lowest amount of heat in the transmission and keep the engine in the most efficient torque range. Depending on where you are, that may or may not be practical. Most people don't want to idle around everywhere they go, so compromising and trying to minimize stress/heat while having the jeep perform how you want it to

On small 37's (Closer to 35.75) 5.13's, and Jeeps .67 final OD gear; I'm running around 2400RPM at 75MPH. This is perfectly comfortable to me and as fast as I really have any desire to drive my Jeep. I really enjoy the deeper gears around town and at lower speeds, I feel like it reduces stress and heat on the Jeep in stop and go traffic and especially when I'm pulling my boat (5K+ when loaded up). It also puts the Torque right in line with the torque curve for the 3.6 as far as efficiency goes.

If my needs/driving style was different, I definitely would have considered a different gear ratio. Then again if I wanted a vehicle where I would primarily be doing 80+ MPH, a Jeep would probably be my last choice. At the end of the day we are driving bricks on wheels. No gearing will make up for the piss poor aerodynamics of a Jeep windshield.

Put 35s on my 2021 JTM soon after buying it new. The 4:10 gears seemed totally fine. I didn't notice a difference. Moved up to 37s a few months ago. Drives like it is wheezing (slower off the start, feels like it struggles. No pep in its step. Regearing to 4:88 next month. Going from 35s to 37s made a noticeable difference to me.

 

[Stan H]

JScan is pretty cool. You manually input the tire size. I will have to check it again. All in with parts was like $75. Full access to the VIN you pay $10 for. It's what teh dealership uses, So i've been told.

Now I aint saying I am right but I have seen several post from different guys that said the true size of the tire is at your inflated amount and height while mounted . Ask me why the flashcal chose 33.25 and the spedometer is dead on. And I will tell you cause at the inflation amount I run plus the weight that's what the computer figured up . ..trust me I tried manually entering 35 and 34.5 was terrible ..

 

[AstroZombie]

Well if i can get it to read better gas mileage teh boss might ease up a little LOL

 

[RubiWhiteGladiator]

This topic has been brought up ad nauseam. You can get by with stock 4.10s and many do, but a regear will be beneficial. Many factors play a role such as type of driving/offroading, weight of set up, and type of terrain you live in to name a few. Do a google search/search on this forum. There's a shit ton of info.

I agree with RodRecket, it all depends on your set up and what you plan on doing. I finally regeared mine to 5.13 and wish I have done it sooner, but my truck is loaded down with a bed cap, RTT, custom drawers in the bed, my gear.

 

[JTGuy]

Re gering will multiply the torque and give it more pep off. the line. My 4.88s help everything run cooler.

 

[Stan H]

Well if i can get it to read better gas mileage teh boss might ease up a little LOL

My usual mileage on 4.10's 35x12.50x17 ran 65mph most of the way and about 40 miles of that was nothing but twists and ups and downs .
I suggest raising your right foot of the go pedal a little

 

[wadewolf]

My usual mileage on 4.10's 35x12.50x17 ran 65mph most of the way and about 40 miles of that was nothing but twists and ups and downs .
I suggest raising your right foot of the go pedal a little

That's around what I get on the stock 33's in mine with 4.10's. I only have about 1400 miles on it so far so im hoping is just break in and it will get a little better after a few hundred more miles.

 

[Stan H]

That's around what I get on the stock 33's in mine with 4.10's. I only have about 1400 miles on it so far so im hoping is just break in and it will get a little better after a few hundred more miles.

It was an 100 mile trip. I run 89 octane in mine and yes mine is well broken in....lol

 

[ttn333]

That's around what I get on the stock 33's in mine with 4.10's. I only have about 1400 miles on it so far so im hoping is just break in and it will get a little better after a few hundred more miles.

Mine is so broken in that it had to spend several weeks at the dealers to replace parts. And I'm still only get around 12mpg, not stock though.

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