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Old 07-21-2013, 01:37 PM   #1
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Gears vs Motor Upgrades

I have a 2004 LJ with 33-12.50's, Iam looking for better drive abilty. Durnig the summer we go to the Serrias and drive Big Bear, so iam driving at altitude and steep roads. My question is should I rear gear (ie 411 have 373 now) or should I put that money into cold air intake cat back exhuast and a programer( tthinking about Banks stinger)?? Will the mootoer upgrades make up for larger tires??

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Old 07-21-2013, 01:49 PM   #2
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Old 07-21-2013, 01:49 PM   #3
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Re-gear. I think you need 4.88s with the 42rle. The cold air intake/cat back/programmer isn't going to give you what you want. Those bolt-ons are ineffective in an engine that lives at 2500-4000 rpm. They realistically only work at high rpm and Wranglers don't see much time at 5000+ rpm.


p.s. Do you see much off-road and do you have a locker in the rear?
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Old 07-21-2013, 02:34 PM   #4
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It iss about 70-30 road dirt, i plan on puttiing an Eaton E loacker in the rear either way. Wont 4.88's be a bit too much? We drive it to the Sierra and Big Bear.
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Old 07-21-2013, 02:36 PM   #5
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It iss about 70-30 road dirt, i plan on puttiing an Eaton E loacker in the rear either way. Wont 4.88's be a bit too much? We drive it to the Sierra and Big Bear.
what trans? thats perfect for the auto and 33's.
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Old 07-21-2013, 02:38 PM   #6
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There is no bigger bang for the buck than gears.
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Old 07-21-2013, 02:54 PM   #7
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What do you think of the Eaton Elocker? I have not read anything bad about them and have only heard goo from a local offroad shop.
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Old 07-21-2013, 03:19 PM   #8
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What do you think of the Eaton Elocker? I have not read anything bad about them and have only heard goo from a local offroad shop.
We've installed quite a few and haven't had any problems yet.

Personally I like elockers.
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Old 07-21-2013, 03:27 PM   #9
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It iss about 70-30 road dirt, i plan on puttiing an Eaton E loacker in the rear either way.

Cool. I was going to suggest installing a locker if you were going to be in the diffs to re-gear.


Quote:
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Wont 4.88's be a bit too much? We drive it to the Sierra and Big Bear.

A quote from one of the most knowledgeable members on the forum:


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Originally Posted by Jerry Bransford View Post
This may surprise you but for that size tire (roughly a 33"), and with your 4-speed automatic, you want 4.88. Yes, 4.88. The 4-speed automatic has such a steep overdrive ratio, .69, that it reduces the highway rpms too much. I.E. it makes the highway rpms too low.. With that size tire, the engine would lug most of the time with 4.56 and would lug all the time with 4.10. With the 5-speed, 4.56 would be appropriate & with the 6-speed, 4.10 or 4.56 would be appropriate. But with your 4-speed 42RLE automatic transmission, don't even think about 4.10 or 4.56. 4.88 is ideal & will NOT produce excessive highway RPMs.

To give you a little more insight... my last TJ was stolen so I bought a used replacement with 4.88 gears, 35" tires, and the same 4-speed automatic you have. That 4.88 isn't enough gear for its 35" tires, it really needs 5.13 or better 5.38. The engine lugs with 35" tires and 4.88. But that same 4.88 would be ideal for your slightly smaller 33" tires.

I think you'd appreciate the 4.88s even more driving up the mountain roads.
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Old 07-21-2013, 03:46 PM   #10
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Yep might as well add a locker as you will need a different carrier with the new gears. Dana 44 carrier break is 3.73
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Old 07-21-2013, 09:52 PM   #11
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Thanks to all for your advice, I was going to go with 4.56's but now I think 4.88's.
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Old 07-21-2013, 10:40 PM   #12
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GEARS ALL THE WAY. I put a CAI and exhaust on my jeep with 35s.. couldn't even tell the difference. But when I installed 488s holy crap. I think I have a hole new jeep!!!!!!!!!!!!!
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Old 07-21-2013, 11:49 PM   #13
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Gears, gears, and gears. I run 5.13's with 35's with a 42 rle. Does well on road and some dumb tq offroad.
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Old 07-22-2013, 07:27 AM   #14
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should I put that money into cold air intake cat back exhuast and a programer( tthinking about Banks stinger)?? Will the mootoer upgrades make up for larger tires??
that crap will do nothing.

regear to 4.88s and swap the speedo gear.

I run 4.88s with 33s in the Colorado Rockies. You'll also need better brakes & steering upgrades, especially for an LJ. I run Vanco brakes w/ Black Magic Pads, and V8 ZJ tie-rod.

See here: Unlimited04's LJ Build - JeepForum.com
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Old 07-22-2013, 12:57 PM   #15
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How much extended highway driving do you plan to do?

I have a 4.88 gear on a 37" tire with the 4spd auto tranny, at 65-70mph mph I am at ~2100-2300 rpm. I can only imagine what the engine rpm would be on a 33" tire at 70mph. If you don't spend much time on the highway then no problem. I usually keep my OD switch off for in town driving, I have no issue with lugging down the engine as others have stated with OD off, but I am in MI which has no mountains or high altitude.
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Old 07-22-2013, 01:10 PM   #16
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How much extended highway driving do you plan to do?

I have a 4.88 gear on a 37" tire with the 4spd auto tranny, at 65-70mph mph I am at ~2100-2300 rpm. I can only imagine what the engine rpm would be on a 33" tire at 70mph. If you don't spend much time on the highway then no problem. I usually keep my OD switch off for in town driving, I have no issue with lugging down the engine as others have stated with OD off, but I am in MI which has no mountains or high altitude.
I do a lot of highway driving. At 70mph, the engine is turning 2400rpms with 33s...which is exactly where it should be. On the highway, I get anywhere between 15-19mpg, depending how much I can keep my foot out of the throttle.

With 37's, you're lugging the engine, at only 2100rpms, and the transmission is gear hunting a bunch, which is why you have to use the OD off button so much. You'd be better off with at least 5.38s, if not 5.89s.
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Old 07-22-2013, 01:55 PM   #17
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I do a lot of highway driving. At 70mph, the engine is turning 2400rpms with 33s...which is exactly where it should be. On the highway, I get anywhere between 15-19mpg, depending how much I can keep my foot out of the throttle.

With 37's, you're lugging the engine, at only 2100rpms, and the transmission is gear hunting a bunch, which is why you have to use the OD off button so much. You'd be better off with at least 5.38s, if not 5.89s.
I am very happy with my setup, there is no transmission hunting, it will sometimes try to shift into OD in town driving <50mph as I stated, but that is why there is a switch to turn the OD off, but there is no gear hunting.

The 4.0L I6 is very happy cruising at 2000 rpm, extended highway driving at 2400rpm is a bit much for me. If you can get 19mpg at 70mph with your setup that really surprises me.
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Old 07-22-2013, 02:52 PM   #18
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cruising at 2000 rpm

that's not cuising, that's lugging


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extended highway driving at 2400rpm is a bit much for me.

3000 rpm for hours isn't a bit much for the 4.0 let alone 2400 rpm.
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Old 07-22-2013, 03:09 PM   #19
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My old Cherokee (AMC 360/T-15/D-20) would spin at 2700 running at 65. Never was an issue. 4.0 has bigger, stronger main bearings than the 360. 3000 rpm wouldn't be a problem at all.
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Old 07-22-2013, 03:15 PM   #20
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I am very happy with my setup, there is no transmission hunting, it will sometimes try to shift into OD in town driving <50mph as I stated, but that is why there is a switch to turn the OD off, but there is no gear hunting.
the 42RLE is always gear hunting.

I think you'd be really surprised at the difference, if you put some 33s on.

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The 4.0L I6 is very happy cruising at 2000 rpm, extended highway driving at 2400rpm is a bit much for me.
Jeep doesn't think so. A bone stock 05/06 6-speed Rubicon turns 2600rpms @ 70mph. In fact, to show you just how undergeared the 42RLE is from the factory, think about this: A 42RLE/3.73s/29s is kinda like a NSG370/3.73s/35s, without using 1st or 5th.

Here's more on RPMs vs powerband & gearing.

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If you can get 19mpg at 70mph with your setup that really surprises me.
Cruise control is on.

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Old 07-22-2013, 03:36 PM   #21
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To each their own gentlemen. My setup works good for me, I am able to comfortably drive up north, have fun on the trails and dunes and drive home on a tank of gas, I am happy with that and that is what it is all about.
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Old 07-22-2013, 10:53 PM   #22
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Going to 33's on a d35 and want to use 4,88 gears, 4.0 with 4 speed auto. What do you think ? I don't do a lot of highway driving. Not going to lock it. 04 TJ. I'm on 32x11.5's right now

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