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Discussion Starter · #1 ·
Well I think the time has come to bite the bullet and regear. I have a 2010 sport with a Teraflex 2.5" coil lift sporting 35" BFG KOs. From everything I have read it looks like I should go with 4.88s. I am currently running 3.21s and they are fine for town and running forest service roads but as soon as the terrain gets steep and gnarly 4Hi pretty much becomes useless. Me thinks it is definitely time for a regear.

I am not babying this bad boy as I already have some nice custom pin stripes from exploring Narnia!!!

What are the 4.88s like for everyday driving? Will it be like a tractor in town? Will I get back power going up long steep hills on the highway?

Could I live with 4.10s? From what I understand from the dealer if I go beyond 4.10s my warranty is done on that part of the drivetrain. I'm really not too worried about the warranty I want to install what is going to be the most functional. :)

Just some background info for you all. I have about 1500km on it now and at least 1100 are off road! I bought this baby instead of a quad.

Cheers. And thanks for all the info in advance. :)
 

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:cool: Don't know about the 3.21 gears, cause that's pretty HIGH gear'd

My JKU Rubi has 4.10 gears and I've got BIG 33" tires and an auto, but

Rather than regear I've used my AEV Procal Module to fool the tranny into thinking that I've got 5.13 gears and the performance is very adequate, but

With 3.21 gears, I think you should change-don't know about 4.88, cause your gonna have to get a programmer to correct your speeedo-anyway !!

Decision-decision-decision !!

:rofl::rofl: JIMBO
 

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Discussion Starter · #3 ·
I've got a 6spd and I did pick up the AEV procal after I put the new tires on. Amazing how fast that handy little tool works.

If it was a mall crawler I would be good to go, but this bad boy tries to avoid all malls. Lol
 

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I have 4.88's and 35" mud terrains on my 6-speed. Highway over 70MPH is a bit loud (3K+ RPM's), and mileage isn't great (16ish), but I wheel it hard, so they're worth it- Mark W.
 

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thaduke2003 said:
I have 4.88's and 35" mud terrains on my 6-speed. Highway over 70MPH is a bit loud (3K+ RPM's), and mileage isn't great (16ish), but I wheel it hard, so they're worth it- Mark W.
I have the same setup. Do you think it's bad to run your RPMs at 3k for an extended time? I don't drive on the interstate much, so I'm usually at 55-60mph going up north. Haven't taken her very far yet.
 

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Discussion Starter · #6 ·
Not sure about Jeeps as this is my first one. :)

I can tell you that on my single cylinder KLR650 I could do 5000+ RPM for a very long time with no issues. I think redline was around 6500-7000. Estimated lifetime on those engines are around 80,000km.
 

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Running ANY engine at high RPM for a long time will have negative effects on that engine's internals. Heat builds up much more rapidly at higher RPM's due to combustion, friction, etc. That's part of why you get worse fuel economy at high RPM's.
The lower your highway RPM's (within reason), the better your fuel economy SHOULD be. There are, of course, other factors, like wind resistance/drag, tire rolling resistance, and inclines to consider- Mark W.
 

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one other factor to keep in mind the lower the gears the smaller the parts.. dana 30 pinion is already small. Have you thought about a 4:1 t-case gearing?
 

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By the way, just read the whole post over: the warranty thing is a load of crap- they're trying to get you to buy OEM 4.10's and have them install them. ANY re-gear will void your warranty on MOST, if not all, axle parts.

As for swapping t-cases vs. re-gearing, while it's an option for a dedicated off-roader, it doesn't make much sense for a driven rig. Being undergeared is killing the OP's fuel economy and power on-road, which wouldn't be changed one bit by a deeper t-case gearset- Mark W.
 

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Since you have a Sport and 35" tires, 4.88s for a 6 speed and 5.13s for an automatic will give you the best performance and RPM range. Do it once and do it right.
 

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river2c said:
Since you have a Sport and 35" tires, 4.88s for a 6 speed and 5.13s for an automatic will give you the best performance and RPM range. Do it once and do it right.
You think 5.13s fir an auto is a bit much?!?
 

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snopro269 said:
You think 5.13s fir an auto is a bit much?!?
I think its wayyyyy to much. Maybe if you were thinking about running 4+ inches of lift and 37s you would need that gearing.
 

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^ Amount of lift has NOTHING to do with gearing. As for 5.13's, that would be the proper gearing for 35's in the auto. They'd be too much for a 6-speed and 35's, but the auto needs lower gearing to compensate for wider gear ratio spread- Mark W.
 

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:cool: Heh Heh, I was gonna say the same thing Duke, but


^ Amount of lift has NOTHING to do with gearing. As for 5.13's, that would be the proper gearing for 35's in the auto. They'd be too much for a 6-speed and 35's, but the auto needs lower gearing to compensate for wider gear ratio spread- Mark W.
Not near as pleasant as you did !!

:rofl::rofl: JIMBO
 

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thaduke2003 said:
^ Amount of lift has NOTHING to do with gearing. As for 5.13's, that would be the proper gearing for 35's in the auto. They'd be too much for a 6-speed and 35's, but the auto needs lower gearing to compensate for wider gear ratio spread- Mark W.
When you jack a vehicle up in the air that already has awful aerodynamics, you make it even worse. Everything you do performance and weight wise affects the engine and transmission in one way or another.
 

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But re-gearing is NOT the way to compensate for height. Re-gearing is used to compensate for larger tires, as tires act as the last set of gears in the drivetrain. You can lift a vehicle 40 feet, and changing the gear ratio will only change your torque band. Adding power to compensate for lift height, ok, but gearing merely shifts the torque band- it doesn't give you any additional power- Mark W.
 

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Discussion Starter · #17 ·
Ok so it's looking like 4.88s are the way to go. What about 4.56s? Less torque up the hills but lower RPM on the highway (plus better fuel mileage)? I'm not too worried about the fuel economy after I have a badass jeep that I can take anywhere.

Your right regarding the 4.10s. That is the highest that they will install on the lot. Probably because that is the highest gear that mopar manufactures. I'm definitely not even considering 4.10s.

If I'm going to do this I wanna do it right.
 

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Discussion Starter · #19 ·
Did you install 4.56s?
 

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4.56 is good for a mall crawler, and an on-roader, but for rocks, mud, or sand, you want 4.88's. The speed and RPM difference isn't huge (2-300 RPM's on the highway), but the payoff off-road is. Either way, you won't be too badly off, but the extra (well, more quickly delivered :)) torque of the 4.88's will also help in traffic at low speeds- Mark W.
 
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