Gears for 37" tires

[dhurley737]

Real world experience here:
On my JT Rubicon with 38's I went with 5.38's thru a friend's strong recommendation (big time pro in the industry). Some folks give me the but for me I have a great mix of highway, minor towing, and some off-road trails (nothing extreme but more fun). Granted, I went with a 38" tire, but all of you with 35"s and 37"s know damn well you're gonna want 38"s at some point knowing that they fit (and then you'll really hate those 4.11's). With 25 years of driving behind me I know you always wish you went a little bigger, a little faster, a little taller. I just don't mess around with the intermediary stop anymore and go straight full-send (saves a ton of coin along the way as well).
20 years ago I had an XJ with 3.73's and 33" tires and I went to 4.56's on that. Was the single greatest thing I ever did - made the Jeep fun to drive again - and that was just a 4" tire size from 29" stock to 33".
More than likely you'll be better off w/ 4.88's or 5.13's... but if you're keeping that thing for a bit I can't recommend enough going straight to the 38's with 5.38's.

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[WK2JT]

@dhurley737 do you have the manual or auto trans?

 

[dhurley737]

@dhurley737 do you have the manual or auto trans?

Automatic

 

[WK2JT]

Automatic

I also have the Auto on 37’s and trying to decide between the 4.88 and 5.13 gears. Only reason for pause on the 5.13 is [Banned Site]’s review on the loss of passing ability with the 5.13’s. I think 5.13’s would still be better than stock, but just another consideration.

 

[wvyankee2]

I have the 488's with 35" Tires. My trans is extremely happy with this set up. About 2300 rpm's at 70 mph.

 

[Flux]

I also have the Auto on 37’s and trying to decide between the 4.88 and 5.13 gears. Only reason for pause on the 5.13 is [Banned Site]’s review on the loss of passing ability with the 5.13’s. I think 5.13’s would still be better than stock, but just another consideration.

I decided on the 5.13s for mine and am quite happy with the results so far. I have the auto and 37s (36.8"). If I decide to move up to 38s next time, I'll still be good with the set up. During lower speed cruising (45-60), she runs up to eighth gear fairly quick and just stays there as long as I'm at a steady speed. MPG gauge turns nice and green.... If I need to pick up the pace, it has plenty of lower gears to choose from. Highway speed (80-85mph), she'll shuffle between 7th and 8th gear if I hit an overpass or hill, but real time MPG stays between 15-18.

 

[hjdca]

I decided on the 5.13s for mine and am quite happy with the results so far. I have the auto and 37s (36.8"). If I decide to move up to 38s next time, I'll still be good with the set up. During lower speed cruising (45-60), she runs up to eighth gear fairly quick and just stays there as long as I'm at a steady speed. MPG gauge turns nice and green.... If I need to pick up the pace, it has plenty of lower gears to choose from. Highway speed (80-85mph), she'll shuffle between 7th and 8th gear if I hit an overpass or hill, but real time MPG stays between 15-18.

If your speedo is corrected, can you give us the rpm at 75 mph ? Thanks !

 

[Flux]

If your speedo is corrected, can you give us the rpm at 75 mph ? Thanks !

Not 75, but 81mph was around 2600rpm.... I have the Tazer and made the corrections. GPS app confirmed MPH is right on.

 

[hjdca]

Not 75, but 81mph was around 2600rpm.... I have the Tazer and made the corrections. GPS app confirmed MPH is right on.

That is perfect. thanks ! Note: my Rubicon JT is 2500 rpm at 85 mph (4:10s) and manual tranny, so, 6th gear is .72 while the auto tranny 8th gear is .67 , so, yours is perfect. I will go with the same diff gears.

 

[WK2JT]

Not 75, but 81mph was around 2600rpm.... I have the Tazer and made the corrections. GPS app confirmed MPH is right on.

@Flux another month in, how are you enjoying the 5.13s? I’m thinking this is the right ratio for me since I’m going to be at elevation and pulling a trailer.

 

[Flux]

@Flux another month in, how are you enjoying the 5.13s? I’m thinking this is the right ratio for me since I’m going to be at elevation and pulling a trailer.

I’m still very happy with the 5.13s. Currently, my average MPG has increased to 16.5 which is considerably better than it was with 4.10s. Go with the 5.13s, you won’t be disappointed.

 

[GrayGoose]

I have 4.88 in my JK with 37's, but from what I've read on the JL Forum, most people feel like the new 8-speed transmission makes gear swaps less of a necessity. I plan to try out 37's on the factory 4.10s before considering anything.

what did you decide?

 

[Renegade]

what did you decide?

I’ve got 11,000 miles on 37” tires in my JT, and am perfectly happy with the performance with 4.10 gears and the automatic transmission.

 

[GrayGoose]

I’ve got 11,000 miles on 37” tires in my JT, and am perfectly happy with the performance with 4.10 gears and the automatic transmission.

thanks - I have 5k on my 37's but it won't stay in high gears at hwy speeds so I just ordered the 5:13's

 

[Renegade]

thanks - I have 5k on my 37's but it won't stay in high gears at hwy speeds so I just ordered the 5:13's

I solved the issue of it not staying in 8th gear by turning off the gear display. I don’t mind if it’s in 6th (1:1), 7th (OD), or 8th (OD2), as long as it performs well. I’m sure 5.13 gears will be even better though.

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