6 speed gear decision input needed

[JackyB88]

I ran 35s with 4.10s for the first year. Only on the relatively steep uphills did I really wish I had more gear. I've got 37s on now, still stuck with 4.10s, spend most time in 4th. If you're sticking with 35s, I wouldn't go more than 4.56. If you're gonna run the 35s for a while and then go to 37s, I'd say 4.88. If you're gonna hit the 37s and maybe 38s, go 5.13. Here's some tables I built to help visualize what sizes/ratios would be doing across the board.

Tire Size

36.8​

Tire Size

36.8​

Tire Size

36.8​

Tire Size

36.8​

Axle Ratio

4.10​

Axle Ratio

4.56​

Axle Ratio

4.88​

Axle Ratio

5.13​

Rev

1st

2nd

3rd

4th

5th

6th

Rev

1st

2nd

3rd

4th

5th

6th

Rev

1st

2nd

3rd

4th

5th

6th

Rev

1st

2nd

3rd

4th

5th

6th

Hi

4.49​

5.13​

2.63​

1.53​

1​

0.81​

0.72​

Hi

4.49​

5.13​

2.63​

1.53​

1​

0.81​

0.72​

Hi

4.49​

5.13​

2.63​

1.53​

1​

0.81​

0.72​

Hi

4.49​

5.13​

2.63​

1.53​

1​

0.81​

0.72​

1500​

9​

8​

15​

26​

40​

49​

56​

1500​

8​

7​

14​

24​

36​

44​

50​

1500​

7​

7​

13​

22​

34​

42​

47​

1500​

7​

6​

12​

21​

32​

40​

44​

1750​

10​

9​

18​

31​

47​

58​

65​

1750​

9​

8​

16​

27​

42​

52​

58​

1750​

9​

8​

15​

26​

39​

48​

55​

1750​

8​

7​

14​

24​

37​

46​

52​

2000​

12​

10​

20​

35​

53​

66​

74​

2000​

11​

9​

18​

31​

48​

59​

67​

2000​

10​

9​

17​

29​

45​

55​

62​

2000​

10​

8​

16​

28​

43​

53​

59​

2250​

13​

12​

23​

39​

60​

74​

83​

2250​

12​

11​

21​

35​

54​

67​

75​

2250​

11​

10​

19​

33​

50​

62​

70​

2250​

11​

9​

18​

31​

48​

59​

67​

2500​

15​

13​

25​

44​

67​

82​

93​

2500​

13​

12​

23​

39​

60​

74​

83​

2500​

12​

11​

21​

37​

56​

69​

78​

2500​

12​

10​

20​

35​

53​

66​

74​

2750​

16​

14​

28​

48​

73​

91​

102​

2750​

15​

13​

25​

43​

66​

82​

92​

2750​

14​

12​

23​

40​

62​

76​

86​

2750​

13​

11​

22​

38​

59​

72​

82​

3000​

18​

16​

30​

52​

80​

99​

111​

3000​

16​

14​

27​

47​

72​

89​

100​

3000​

15​

13​

26​

44​

67​

83​

93​

3000​

14​

12​

24​

42​

64​

79​

89​

3250​

19​

17​

33​

57​

87​

107​

121​

3250​

17​

15​

30​

51​

78​

96​

108​

3250​

16​

14​

28​

48​

73​

90​

101​

3250​

15​

14​

26​

45​

69​

86​

96​

3500​

21​

18​

36​

61​

93​

115​

130​

3500​

19​

16​

32​

55​

84​

104​

117​

3500​

17​

15​

30​

51​

79​

97​

109​

3500​

17​

15​

28​

49​

75​

92​

104​

3750​

22​

20​

38​

65​

100​

124​

139​

3750​

20​

18​

34​

59​

90​

111​

125​

3750​

19​

16​

32​

55​

84​

104​

117​

3750​

18​

16​

30​

52​

80​

99​

111​

4000​

24​

21​

41​

70​

107​

132​

148​

4000​

21​

19​

37​

63​

96​

119​

133​

4000​

20​

17​

34​

59​

90​

111​

125​

4000​

19​

17​

32​

56​

85​

105​

119​

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[hephaestus]

I have a 2018 JLUR w/6spd on 35's. 4.10's sucked on the highway and if I was even towing a 1000lbs jetski, it was futile. I just put 4.88's in last week. They are perfect for a Jeep that still sees highway miles. I can use 5th and 6th gear again now and actually tow. On steep boat ramps pulling a double set of jet skis out of the water before was dangerous. I had to use 4low or I would burn my clutch up so bad that I was afraid I was going to slip back into the water. Now I can get them out in 2wd without worry. 5.13's would be nice but not if you see interstate use. I'm at about 2200rpm in 6th gear doing 80 now and it's perfect. I did lose about 1mpg from 4.10 to 4.88 though. That kinda sucked and would suck even more with 5.13's.

 

[Blacksport]

I’m about to get my wife’s Jeep regeared. Hers is also a 6 speed but a sport. Her Sport has my original Rubi axles under it with the stock 4.10’s.

A 2024 Sport or Sport S has a 3.45 axle ratio as stock. The Willys & Rubicon have 4.10 ratios. A 4.56 ratio is a no-charge option. The Sport models have no optional ratios.

 

[Apples491]

I'm on 37s with factory 4.88s at elevation. The Jeep always felt sluggish, like a little worse than stock gearing (4.10/33s). I got it tuned by Brad and it's a whole new vehicle.

That being said, at your elevation 4.56s would probably be fine. If you think you'll be taking it into the Rockies occasionally go with 4.88s. 5.13s are way too tall for any sort of daily driver.

With 4.88s your RPMs in 6th gear on the highway will be a little high but shouldn't be terrible. I'll second using the grimjeeper calculator above. Figure out what final drive rpms would be in each ratio and then hit the highway and put yourself in whatever gear gets you to that RPM and assess if you could live with it. Not a perfect comparison but gives you an idea.

 

[double0762]

I’m about to get my wife’s Jeep regeared. Hers is also a 6 speed but a sport. Her Sport has my original Rubi axles under it with the stock 4.10’s. We recently did a small lift and 35x12.5-17 tires on my original Rubi wheels. Hers will never go bigger than 35’s and the 4.10’s just don’t cut it on the highway. We recently went to OKC from Amarillo and was in 5th pretty much the entire just to be able to go the speed limit of 75. 6th couldn’t maintain that speed even on flat road.

Those that have 35’s on a 6 speed, 4.88 or 5.13? I’m leaning towards 4.88 for the bigger pinion, but that’s not a huge deal on hers it’ll see some dirt roads and light trail use

I went with 4:56 gearing for my 6 spd. Plenty of power thru the gears and I have no problem with 6th gear on the highway

 

[roaniecowpony]

If you're willing to adjust your top cruise speed to keep the rpm at a comfortable level, 4.88 should work fine. But if you absolutely want an exact speed for cruise, you'll need to be exact for the gear choice. I find that the 2300 rpm cruise works for me.

 

[siggy]

If you haven't tuned it, I'd highly suggest that. Game changer especially with the manual - pretty much transforms the Jeep.

Which tires did you put on? I don't necessarily see the issue with running it in 5th. Wouldn't that put you in the same rpm range as 6th w/ 4.88's?

 

[hephaestus]

If you haven't tuned it, I'd highly suggest that. Game changer especially with the manual - pretty much transforms the Jeep.

I TOTALLY concur. BMP Tuning on here did mine and it's the single best thing I've ever done to it. I still wanted 4.88's for my 35's afterwards though.

 

[6.2Blazer]

If you do the math, 4.56 gears in 6th gear gives you almost the exact same RPM at speed as 4.10 gears in 5th gear. So on paper going to 4.56 gears would let you run in 6th gear in the same situation. However I will say that going from 4.10 to 4.56 is a pretty small change considering how much it costs. Part of this is that 5th and 6th gears are really close to each other. If you are going to change gears I would recommend going to 4.88 to make a noticeable difference. Going to 4.88 gears only bumps up the RPM at 75 mph by around 140 RPM as compared to driving in 5th gear with the 4.10's.
But with that said, I'm not completely sure what made the drive "miserable"? What is the difference between driving down the freeway in 5th gear with 4.10s at 2,400 RPM versus running in 6th gear with 4.56 at the same RPM? Sure, it's nice to have use of all 6 gears but there isn't any issue running in 5th, and you shouldn't notice any difference. You simply aren't going to notice much, if any, difference during take off between 4.10 and 4.56.

 

[CorvZ061]

If you do the math, 4.56 gears in 6th gear gives you almost the exact same RPM at speed as 4.10 gears in 5th gear. So on paper going to 4.56 gears would let you run in 6th gear in the same situation. However I will say that going from 4.10 to 4.56 is a pretty small change considering how much it costs. Part of this is that 5th and 6th gears are really close to each other. If you are going to change gears I would recommend going to 4.88 to make a noticeable difference. Going to 4.88 gears only bumps up the RPM at 75 mph by around 140 RPM as compared to driving in 5th gear with the 4.10's.
But with that said, I'm not completely sure what made the drive "miserable"? What is the difference between driving down the freeway in 5th gear with 4.10s at 2,400 RPM versus running in 6th gear with 4.56 at the same RPM? Sure, it's nice to have use of all 6 gears but there isn't any issue running in 5th, and you shouldn't notice any difference. You simply aren't going to notice much, if any, difference during take off between 4.10 and 4.56.

It’s more trying to get it to where I can drop down to 5th for the hills instead of dropping to 4th which is a bigger step. I’d really like to get some mileage back too if I can, that 11.5mpg kinda stung

 

[GabeBoyTheGreat]

I ran 4.56s on 35s in my now sold 2018 JL Sport. Currently, I have 4.10s and 33s in my 2025 JLU Willys.

Based on my experience, 4.10s/33s and 4.56s/35s are adequate combinations, but just barely. When I eventually go to 35s on my Willys, I will without question go with 4.88s.

The only downside to 4.88s is slightly higher RPM on the highway, but you are still only running about 2,500 RPM at 75 MPH in 6th gear, which I would still consider very reasonable for a DD.

I will gladly take that slight increase in highway RPM to improve torque in gears 1-5 and R.

Due to the lightweight flywheel, starting off in 1 or R can be a chore sometimes. Lower gearing helps offset that a little bit.

The struggle with higher gearing with this particular tranny is that there isn't always a lower gear "available" if the current gear isn't cutting it. 4-6 are close together, so you can just downshift if the current gear isn't cutting it. The problem is the lower gears, 2-4. If you are struggling with those gears (happens frequently for me) and you try to downshift, the engine revs up to like 4k+ RPMs becausethe gear spacing is so wide. Personally, I don't like to rev that high just to cruise. If I am accelerating, sure, but not while cruising.

So really the only option (for me) is to opt for the slightly lower gearing (4.88) in hopes that I don't have to downshift as often.

Additionally, 2nd and 3rd gears are essentially the only 2 acceleration gears for highway speeds, but with 4.56s on 35s, 3rd gear tops out at 95 MPH. Since I will never reach that speed in my Jeep, that means that I am leaving that high end power on the table. Going to 4.88s brings the top speed of 3rd gear down to 89 MPH. It still leaves some high end power on the table, but definitely an improvement over 4.56s.

I also recommend the tune, but to me, that is not a substitute for proper gearing.

 

[LKG]

I had 4,88s with 35s on my last one. I think it was perfect.

Did you still start in 1st? Or did you jump to 2nd??

 

[Maverick909]

I’m about to get my wife’s Jeep regeared. Hers is also a 6 speed but a sport. Her Sport has my original Rubi axles under it with the stock 4.10’s. We recently did a small lift and 35x12.5-17 tires on my original Rubi wheels. Hers will never go bigger than 35’s and the 4.10’s just don’t cut it on the highway. We recently went to OKC from Amarillo and was in 5th pretty much the entire just to be able to go the speed limit of 75. 6th couldn’t maintain that speed even on flat road.

Those that have 35’s on a 6 speed, 4.88 or 5.13? I’m leaning towards 4.88 for the bigger pinion, but that’s not a huge deal on hers it’ll see some dirt roads and light trail use

4.88 is over kill for highway and 35's. I have a 6 speed manual running 4.88 and 37's. you would do much better with 4.56.

when i had the 4.88 and 35's at 70 MPH you will be running mid to low Teens for MPG and 28-29 hundred rpm

 

[Maverick909]

I ran 4.56s on 35s in my now sold 2018 JL Sport. Currently, I have 4.10s and 33s in my 2025 JLU Willys.

Based on my experience, 4.10s/33s and 4.56s/35s are adequate combinations, but just barely. When I eventually go to 35s on my Willys, I will without question go with 4.88s.

The only downside to 4.88s is slightly higher RPM on the highway, but you are still only running about 2,500 RPM at 75 MPH in 6th gear, which I would still consider very reasonable for a DD.

I will gladly take that slight increase in highway RPM to improve torque in gears 1-5 and R.

Due to the lightweight flywheel, starting off in 1 or R can be a chore sometimes. Lower gearing helps offset that a little bit.

The struggle with higher gearing with this particular tranny is that there isn't always a lower gear "available" if the current gear isn't cutting it. 4-6 are close together, so you can just downshift if the current gear isn't cutting it. The problem is the lower gears, 2-4. If you are struggling with those gears (happens frequently for me) and you try to downshift, the engine revs up to like 4k+ RPMs becausethe gear spacing is so wide. Personally, I don't like to rev that high just to cruise. If I am accelerating, sure, but not while cruising.

So really the only option (for me) is to opt for the slightly lower gearing (4.88) in hopes that I don't have to downshift as often.

Additionally, 2nd and 3rd gears are essentially the only 2 acceleration gears for highway speeds, but with 4.56s on 35s, 3rd gear tops out at 95 MPH. Since I will never reach that speed in my Jeep, that means that I am leaving that high end power on the table. Going to 4.88s brings the top speed of 3rd gear down to 89 MPH. It still leaves some high end power on the table, but definitely an improvement over 4.56s.

I also recommend the tune, but to me, that is not a substitute for proper gearing.

no way 2500 at 75mph with 4.88s and 35's I run 4.88 and 37's at 2650 at 75mph

 

[JeepinPete]

It’s more trying to get it to where I can drop down to 5th for the hills instead of dropping to 4th which is a bigger step. I’d really like to get some mileage back too if I can, that 11.5mpg kinda stung

If your mileage was that bad you must have been bucking one helluva headwind. Regardless, swapping gears isn't going to help mpg's.

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