Best Gears for 35's?

[Jeeperjamie]

Max tow with 35’s everything else is stock, I don’t really go highway but maybe once a week and average on the dash 18.6, live in upstate ny where it’s moderately hilly, any rd where I can get 55-60 she is in 8th no problem, still is plenty of passing power when needed on actual highway, when I drive with a lighter foot I’ve seen over 20mpg on the average, and my truck has constant 150-300 in bed depending what tools I need for work that day

For this same reason is why I question the need for 4.88 gears on mine and just 4.56 gears. I don't plan on going bigger than 37's and a light 37 under 80lbs. I see over 17 in mine on 37's and saw the same numbers your getting when I had 35's. I feel like unless your towing to the max you will see the best performance on 37's with 4.56 gears on the JT with the 8spd trans.

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[SteveH85355]

I read in one Forum that 4.88s will work fine with 35s too, but I thing that combination will be to much.

I regeared my Rubicon to 4.88s after installing 35s. I LOVE IT! Gas mileage has stayed the same, usually in 8th by 45 and almost never downshifts @ highway speeds. Yes, it runs 2200 rpm @ 70 mph but given the complete and total lack of power below 2000 rpm the engine never lugs.

 

[dcmdon]

I don't know what combination will give this. But if I'm driving on the highway in my truck. (35s and 4.10 gears)

At 70 mph it can't really maintain speed up even the slightest incline in 8th. I'm turning about 2000 rpm.

In 7th, its turning about 2500 rpm and can maintain speed, but is noticeably louder. Not loud. Just a bit more engine noise.

So something that has the engine turning about 2300 rpm at 70 might seem just right.

Some back of hte napkin math. (Not by any means difinitive)

(4.1 x 2300)/2000 = 4.71

So 4.71s will get me to 2300.

4.71s don't exist.

So some more math (2000 x 4.88) / 4.10 = 2380 rpm at 70 mph

(2000 x 4.56) / 4.10 = 2224 rpm at 70 mph.

I'd lean towards more rpm just for the ease of driving. So I'd probably do 4.88s.

 

[macgyvr]

I'm thinking about 5.38s and 35s...37s maybe in the future...

The pin is the same size from 4.88? So nothing lost, nothing gained?

My highway cruising speeds are 70-75...still reasonable rpm...

Gas mileage isn't a big deal, 13k miles on mine since new in Nov 19, I have a work car to dd.

Too poor to do this twice.

mac 'Am I crazy?' gyvr

 

[T-Rock]

Interesting thread, late to the party, but 2 cents anyway.
I have a JT Mojave, 4.10 gears, running 35" BFG KO2.s with a SmartCap, Frontrunner rack and Decked system. I used a Tazer to size the tires and get shifting on the 8-speed auto to fall in line.

I know I run with roughly 500 lbs load at all times due to that stuff and the gear in the drawers.
I get 14.6-15.2 MPG on the highway (typically mixed with lots of hills, some mountains, some flat).
If I am towing we are looking at 9 MPG.
I also only get into 8th gear once in awhile on the freeway (downhill), typically in 5th or 6th at 65-70mph.
I raised my tire pressure from 36 to 38/39 due to the weight and to see how it impacted both shifting and mpg. Shifting improved a bit, I now hit 8th a tiny bit more frequently but I get into 7th gear more often. My mpg stays closer to 15 now.

I set this up this way so I wouldn't have to load/unload recover gear, tools, etc. all the time.
I know if I stripped it down that would help mpg, but honestly, I didn't think it would impact shifting much. Maybe that isn't the cause, I don't know.
I don't really think I will go to 37's or larger, I don't do rock crawling or difficult trails & don't think it is worthwhile to add a lift and regear to go to larger tires (unless I win the lotto) for what I do.

So...is it purely the extra weight or am I just to much of a lead-foot?
OR would 4.56 or 4.88 gears help?

 

[JTGuy]

With my '22 JTR and 4.10s with 315KO2s it does just fine. Going to BFG KO2 in 37 (36.5) and was going to do 4.88s but now thinking that 4.56 might be better for all the freeway I do. That way I can easily go back to 35s. In the 8 speed trans 6th is 1:1 so it's the strongest there. 8th is .67 and probably the weak one.

 

[macgyvr]

I ended up going 5.13s with 35s. I love it. Have about 5k miles on the gears. Just went to Moab from Indiana. 11 days driving the Jeep. Got about 17 mpg on the highway running 70-75 mph (2500-2650 rpm). The thing absolutely has power.

Photo shows mpg for entire trip which included 5 days of wheeling in Moab. The truck was ridiculous off road. My 5th trip to Moab (first in JTR), it was a blast.

mac 'no regrets' gyvr

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