3.6L, 8 AT, 37”: 4.88 or 5.13?

Reseg

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Awesome, thanks. I wonder if anyone with 5.13 gears can chime in with downshift behavior during WOT from 8th gear? The video I saw stated that the transmission wouldn’t go below 6th in this situation. The video was posted by “he who shall not be named here”.
Keep in mind this is the V6 and it was shifting at redline. Doesn’t the 2.0 have a lower redline? So it would shift sooner and maybe not shift as far down gears.





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In that video, he is complaining about 4th at 70mph with 5.13s. When doing 67mph in 4th, it's at redline, so it makes sense.

5th was achieved at 70mph automatically.
 

Reseg

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I never see 8th under 50mph. What does this do for your overall fuel economy? Since upgrading to 37s my JLUR gets approx 280 miles per tank, averaging 14mpg.

@Reseg
Did you have a good baseline of your before and after mpg change?
No, I modified it right after getting it. I was surprised to see it in 8th @ 46mph so I video'd it. I usually don't pay attention to the gear. The places I drive are horrible for MPGs, constant stop signs and 75-80mph toll road every few weeks. I always get way less MPGs than a vehicle is rated at. I drove a brand new Civic for a bit I got for my daughter, rated at 32 city, 42 highway, and I was getting 23 with it in eco mode.
 

Redbaron73

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I drove a brand new Civic for a bit I got for my daughter, rated at 32 city, 42 highway, and I was getting 23 with it in eco mode.
This sounds a lot like my driving.
 

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@Chocolate Thunder - I ordered the Dana Spicer master install kits for the front and rear axle yesterday which leaves me to decide on the gear ratios soon. As you have seen me post, I am on the fence as well, but between 4.56 and 4.88. From my viewpoint with 35" tires, 4.56 would put me about where I was with 33" tires and 4.10.

4.88 would give me a bit more "ummpf" with 35" tires and if I were to move up to 37" (doubtful, but never say never) it would have me just about where I was with 33" tires and 4.10.

Truth be told, I was not really that happy with 4.10 and 33" tires because I hate the constant up and down shifting when driving into a headwind or slight inclines. I have always opined that FCA should have installed 4.56 from the factory and while I know that 5.13 is not for me, I am leaning very hard to 4.88.

Thoughts?
 
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Chocolate Thunder

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@Chocolate Thunder - I ordered the Dana Spicer master install kits for the front and rear axle yesterday which leaves me to decide on the gear ratios soon. As you have seen me post, I am on the fence as well, but between 4.56 and 4.88. From my viewpoint with 35" tires, 4.56 would put me about where I was with 33" tires and 4.10.

4.88 would give me a bit more "ummpf" with 35" tires and if I were to move up to 37" (doubtful, but never say never) it would have me just about where I was with 33" tires and 4.10.

Truth be told, I was not really that happy with 4.10 and 33" tires because I hate the constant up and down shifting when driving into a headwind or slight inclines. I have always opined that FCA should have installed 4.56 from the factory and while I know that 5.13 is not for me, I am leaning very hard to 4.88.

Thoughts?
I originally went to 35 and considered 4.56. Most everyone who knows more than me told me to “never say never” as far as going with bigger tires (37 now) and that it’s not enough of a difference in going to 4.56 to justify the cost. That’s a matter of opinion of course. I was also advised that since I’m spending $2K I might as well get a little more grunt than I had with the original 4.10 and 33. 37 and 4.88 seems to be a sweet spot. But I believe that even if I were still on 35 I’d go 4.88 over 4.56. 5.13 is more gear than I want or need and I’m confident that I won’t increase tire size any further.
 

CarbonSteel

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I originally went to 35 and considered 4.56. Most everyone who knows more than me told me to “never say never” as far as going with bigger tires (37 now) and that it’s not enough of a difference in going to 4.56 to justify the cost. That’s a matter of opinion of course. I was also advised that since I’m spending $2K I might as well get a little more grunt than I had with the original 4.10 and 33. 37 and 4.88 seems to be a sweet spot. But I believe that even if I were still on 35 I’d go 4.88 over 4.56. 5.13 is more gear than I want or need and I’m confident that I won’t increase tire size any further.
Great minds think alike. I will be ordering both sets of 4.88 gears this coming week. Thanks for your thoughts.
 

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very informative. Thanks for posting these vids .. 4:88 for me
 

Tdog495

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Also downshifting to 4th gear (for passing speed) on 4:88’s is a good thing. Simply because it will quickly shift to 5th and that creates that passing power.
Downshifting from 5th is not so good. (5:13’s). When u downshift to
5th it takes longer to get to 6th, and u wouldn’t get that instant passing speed
 

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How do you guys get the little gear subscript on the D? Is this a Tazer thing?
 

Jeepmarkjl

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im bumping up to 35s next week which Im told the 4.10 on my Rubicon is fine. But if I ever want to go to 37 I should do 4.88. Im not towing anything really (except for my fat a&&). so here's the question: I see two types of regear options on websites: Just the Axel Gear ring and Pinion or the whole rebuild kit (which is a lot more expensive). So whats really needed? Axel Ring/Pinion option or the full rebuild?
 

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@Chocolate Thunder

just finished a mostly interstate and highway (with stoplights) route i frequently drive.

3” lift, 37’s, 4.88’s, 3 occupants, 400lbs of cargo from northern MD to central VA.

203.7miles. Displayed MPG 19.7; hand calc was 20.3.

7th was frequently used on hills, but nothing i to 6th i can recall that wasnt speed related. So, i expect it to go to 7th time to time for hills to maximize 8th cruise, as it It still overdrive. The trans never felt “busy” or “undecided” about its gear. I found the drive perfect.

given the conditions, the 4.88 gears accounted for passengers, 3” of lift/airdrag, and 400lbs of cargo while losing less than 1 MPG along that same route when compared to stock height/37’s/stock gears/no cargo.

hope that helps.
 
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Chocolate Thunder

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@Chocolate Thunder

just finished a mostly interstate and highway (with stoplights) route i frequently drive.

3” lift, 37’s, 4.88’s, 3 occupants, 400lbs of cargo from northern MD to central VA.

203.7miles. Displayed MPG 19.7; hand calc was 20.3.

7th was frequently used on hills, but nothing i to 6th i can recall that wasnt speed related. So, i expect it to go to 7th time to time for hills to maximize 8th cruise, as it It still overdrive. The trans never felt “busy” or “undecided” about its gear. I found the drive perfect.

given the conditions, the 4.88 gears accounted for passengers, 3” of lift/airdrag, and 400lbs of cargo while losing less than 1 MPG along that same route when compared to stock height/37’s/stock gears/no cargo.

hope that helps.
That’s a huge help, thank you for the details. I’ve never gotten mileage like that even stock except once on a straight trip going 63 mph the whole way. Got 19.xx. Now with the 2.5” lift, 37s, and 4.10 I get 15.5-17 on the highway.
 

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