4.56 vs 4.88 3.6 on 37s

Slavens said:
I am running 37's with 5:13's with a PR44 up front and it's been awesome so far drives easy MPG @ high 16's that's with 70MPH on the HWY.
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High 16's is pretty good, I'm hoping for 15-16 personally. The only thing that still has me on the fence is 75-80mph, which happens on the way to the trail fairly often and on the way to work (DD). Looking at the 3.6 RPM chart @ 70mph 4.88 with 37s (technically 36.75 is almost exactly the stock tires (31s) at 4.10 gears.

Thanks for all the input, I am somewhat leaning toward the 5.13 now, even the shop recommended it, but I was really looking for the balance between performance and gas mileage, even though its a jeep...
 
JKsix said:
What are y'all's thoughts on 5.38 gears with 37s and a 3.8L?
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Your gear teeth will be small and you run a higher risk of breaking them on the trail, especially if you love the skinny pedal. However, based on this chart it looks like it will be a good fit with your 3.8 and auto transmission.
gallery_2_46_206669.jpg

If you go through with it, remember that your ring and pinion are a weak point now.
 
MR.Ty said:
Your gear teeth will be small and you run a higher risk of breaking them on the trail, especially if you love the skinny pedal. However, based on this chart it looks like it will be a good fit with your 3.8 and auto transmission.
View attachment 151447

If you go through with it, remember that your ring and pinion are a weak point now.
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Thanks for posting these! It's a jeep I am looking into purchasing and it's a stick, so by these charts the jeep is in the blue and good to go.
 
5.13 would be too much for a Dana 30 correct? I was set on 4.88 but I know I want 5.13 eventually. Have to dump these 3.21 gears. I don't plan on pr44 until this axle takes a shit...
 
JRied said:
5.13 would be too much for a Dana 30 correct? I was set on 4.88 but I know I want 5.13 eventually. Have to dump these 3.21 gears. I don't plan on pr44 until this axle takes a shit...
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Yeah, 5.13s aren't going to end well unfortunately in a D30. Stick with the 4.88s.
 
JRied said:
5.13 would be too much for a Dana 30 correct? I was set on 4.88 but I know I want 5.13 eventually. Have to dump these 3.21 gears. I don't plan on pr44 until this axle takes a shit...
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While it is not recommended, ill be probably going this route, I don't want to spend money twice. I plan on getting a pr44 as well once my 30 hits rock bottom lol

If you do happen to go this route DO NOT lock the front.
 
JRied said:
5.13 would be too much for a Dana 30 correct? I was set on 4.88 but I know I want 5.13 eventually. Have to dump these 3.21 gears. I don't plan on pr44 until this axle takes a shit...
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Don't regear until you get the pr44 you will be better off saving it for the pr44. 1k regear for the front is about 20% or a pr44
 
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