Talk me out of 4.88 re-gear

Mean Green

Mean Green

New Member
Supporting Member
Joined
Sep 2, 2019
Messages
17
Location
Casper
Hey guys and gals, I just bought a new jeep but it's been modified already and want to scale it back. Currently has 4.5 bds lift with 37 Goodyear tires. Stock Dana 44 rear and Dana 30 up front. Has not been regeared yet. I'm thinking of going down to 35's and regearing to 4.88. this needs to be a daily driver weekend warrior do everything type of jeep. Not all jeeps need to be rock crawlers in my opinion. Am I crazy for thinking of going it down? Pics of rides appreciated with 35's and 4.5 inch lift.

610.jpeg
 
My 2016 Rubicon has 315 KO2s and the factory 4.10 gears. It feels pretty damn near perfect with that setup, but I think it would be slightly better if it it was geared to 4.56... that would IMHO be the perfect combination for 35s. However, I also don't feel that going to 4.88 is going to be that much more noticeable over 4.56. That being said, I think 4.88 would actually work great.
 
  • Like
Reactions: Wunfeather
Mean Green said:
2016 3.6 with 5 speed automatic
Click to expand...

I live in the mountains and my wife daily drives the JKU to work from 2000 foot elevation where we live to over 5000'. it has an automatic with stock 4.10:1 gears with 35" tires. it pulls the hills great and has plenty of power. my lift is only 3.5"
 
nice looking JK by the way and welcome to the Forum. Not sure what 35's wouId look like with those fenders, do you have the full fenders? I really like the Sublime Green color
 
I will be getting the original fenders and painting to match. Agreed it would be too much for 35's. I love the obnoxious color. Lol. So should I look at 4.56? Sounds like even 4.10 is enough
 
Mean Green said:
I will be getting the original fenders and painting to match. Agreed it would be too much for 35's. I love the obnoxious color. Lol. So should I look at 4.56? Sounds like even 4.10 is enough
Click to expand...
some would say 4.56 isn't enough but coupled with the auto and dropping to 35" tires, I would say its just right. you're probably (hopefully) at 3.73:1 now or worse 3.21:1 with 37's, how does it drive?
 
So I am currently on 3.21. It's really not terrible to be honest. Slow but I'm getting 16 mpg in town. Hills suck of course but the jeep handles it surprisingly well
 
Found a chart that says rpm is 2445 with 35's and 4.56 gears. If I stay on 37's the same would be true with 4.88. Any fears I should have for a daily driver weekend warrior if I stay on 37's with 4.88 gears and a Dana 30 up front? Thinking I'll sleeve it and weld gussets on inner C's for strength. Would this be enough?
 
The 35" tire diameter is reduced to a more realistic size.

NAG1/4.10/34" = 2522rpm @ 75mph
NAG1/4.56/34" = 2805rpm @ 75mph
NAG1/4.88/34" = 3001rpm @ 75mph

NAG1/4.10/36" = 2382rpm @ 75mph
NAG1/4.56/36" = 2649rpm @ 75mph
NAG1/4.88/36" = 2835rpm @ 75mph
 
  • Like
Reactions: DrDmoney
Mean Green said:
Found a chart that says rpm is 2445 with 35's and 4.56 gears. If I stay on 37's the same would be true with 4.88. Any fears I should have for a daily driver weekend warrior if I stay on 37's with 4.88 gears and a Dana 30 up front? Thinking I'll sleeve it and weld gussets on inner C's for strength. Would this be enough?
Click to expand...
I wouldn't run a D30 with a 37 period
 
Mean Green said:
Found a chart that says rpm is 2445 with 35's and 4.56 gears. If I stay on 37's the same would be true with 4.88. Any fears I should have for a daily driver weekend warrior if I stay on 37's with 4.88 gears and a Dana 30 up front? ...
Click to expand...

Be careful of the charts. Does it include the overdrive ratio?

What does a stock JK run for rpms at 75mph?
 
  • Like
Reactions: DrDmoney
That chart does say overdrive and only says 70 mph after looking closer at it. I'll never drive much over 70 anyway.
 
Mean Green said:
That chart does say overdrive and only says 70 mph after looking closer at it. I'll never drive much over 70 anyway.
Click to expand...

Overdrive for your specific transmission?

The point here is that this is a fairly simple math problem. And gear ratios are not very mysterious. A stock JK ran various gear ratios for it's tire and transmission combinations. Knowing what those were is a good starting point for deciding what to choose for a larger tire.
 
  • Like
Reactions: StG58
Top Bottom