Gearing options - Pirate4x4.Com : 4x4 and Off-Road Forum

whitetrashxj · 03-01-2011, 04:55 PM

Sorry if I posted this in the wrong section but I don't know where I should put it, feel free to move it if it's not in the right spot,

Anyway,

I'm building my diffs right now, well starting to... And I'm gonna be ordering my gears, I'm not too sure what I should be running for gears so I don't kill my motor but can still do 80-100km/hr on the highway,

What I'm running right now is

4.0L,AW4,np231 with teraflex 4.1 kit, hpD60 front and shaved,disk braked 14 bolt rear,

Tire size, I was thinking 40" tires,

I have a gear calculator on my phone and was thinking I should run 4.88 gears or 5.13,

What I'm worries about with 4.88's is being under powered, and what I'm also worried about is my rpms being too high on the highway with 5.13's anyone shine some light on this for me before I go and buy the wrong gears for my jeep?

Thank you
Nick

Rinkrat456 · 03-01-2011, 05:39 PM

There's more to it than highway rpm's. It's highway load. 1 tons and 40+ tires weight a lot more. You NEED to turn those extra revs to keep the engine happy so you're not sucking down gas. 5.13's all the way, especially with the 4.0L. At 100kmh you're only going to be turning 1870 rpm's and that's hardly chugging along on the highway with 5.13's. Expect to downshift any time you hit a slight incline.

Make sure to install a great transmission cooler.

POS YJ · 03-01-2011, 06:49 PM

You WILL NOT be happy with 4.88's!! Go 5.13's, if not deeper. The 4.0 will run fine at 3,000rpm on the freeway if that's what you're worried about.

Justdhutch · 03-01-2011, 09:52 PM

40's? I say 5.38's. That thing is gonna be a pig.

Ho Shorts · 03-01-2011, 10:36 PM

I ran 4.88's with 38" on my XJ and it was on the borderline of being geared too high. 40's DEFINATELY go 5.13 if not 5.38

james@bluetorchfab · 03-02-2011, 07:49 AM

My vote is 5.38's

MonsterSeven · 03-02-2011, 03:42 PM

if you have come this far, what makes you think you are going to stop at 40s? do it once, and do it right, the first time. 5.86s.

Justdhutch · 03-02-2011, 03:59 PM

Quote:

Originally Posted by MonsterSeven

if you have come this far, what makes you think you are going to stop at 40s? do it once, and do it right, the first time. 5.86s.

He can't. 5.38 is as big as they go for the 14b.

Atleast I couldn't find any bigger. If they make 5.86's now I'm gonna be pissed because I just finished my install of 5.38's.

MonsterSeven · 03-02-2011, 04:03 PM

Quote:

Originally Posted by Justdhutch

He can't. 5.38 is as big as they go for the 14b.

Atleast I couldn't find any bigger. If they make 5.86's now I'm gonna be pissed because I just finished my install of 5.38's.

time to find a different rear axle then.

in that case, 5.38s.

Justdhutch · 03-02-2011, 04:21 PM

Quote:

Originally Posted by MonsterSeven

time to find a different rear axle then.

in that case, 5.38s.

If you want a cheap, very strong axle, with disc brakes, you can't go wrong with a 14b. I'm into mine for under $500

14b -$50
5.38's -$150
Disc brake swap -$240 (and I could've went cheaper but got all new parts)

jpfrk2001 · 03-02-2011, 04:29 PM

I have the EXACT drivetrain combo and tire size on my YJ. Go 5.38's Thats what I run

2800 RPM and Im turning around 75 on the Hwy no problem

03-01-2011, 04:55 PM	#1 (permalink)
whitetrashxj Registered User Join Date: Mar 2009 Member # 131296 Location: maple ridge,bc,canada Posts: 44	Gearing options Sorry if I posted this in the wrong section but I don't know where I should put it, feel free to move it if it's not in the right spot, Anyway, I'm building my diffs right now, well starting to... And I'm gonna be ordering my gears, I'm not too sure what I should be running for gears so I don't kill my motor but can still do 80-100km/hr on the highway, What I'm running right now is 4.0L,AW4,np231 with teraflex 4.1 kit, hpD60 front and shaved,disk braked 14 bolt rear, Tire size, I was thinking 40" tires, I have a gear calculator on my phone and was thinking I should run 4.88 gears or 5.13, What I'm worries about with 4.88's is being under powered, and what I'm also worried about is my rpms being too high on the highway with 5.13's anyone shine some light on this for me before I go and buy the wrong gears for my jeep? Thank you Nick __________________ 86 cj-5 frame, 76 cj-5 body, put together on 35" krawlers, 360v8,np435,d300 twin sticked Last edited by whitetrashxj; 03-01-2011 at 05:18 PM.

03-01-2011, 05:39 PM	#2 (permalink)
Rinkrat456 Registered User Join Date: Mar 2007 Member # 88919 Posts: 757	There's more to it than highway rpm's. It's highway load. 1 tons and 40+ tires weight a lot more. You NEED to turn those extra revs to keep the engine happy so you're not sucking down gas. 5.13's all the way, especially with the 4.0L. At 100kmh you're only going to be turning 1870 rpm's and that's hardly chugging along on the highway with 5.13's. Expect to downshift any time you hit a slight incline. Make sure to install a great transmission cooler. __________________ [COLOR="Lime"][I]At 1300rpm's would you rather have 10 extra hp or 10 extra lb-ft of torque?[/I][/COLOR]

03-02-2011, 03:42 PM	#7 (permalink)
MonsterSeven Registered User Join Date: Feb 2008 Member # 108872 Location: Bennington, NE Posts: 781	if you have come this far, what makes you think you are going to stop at 40s? do it once, and do it right, the first time. 5.86s. __________________ 98 RHD TJ: swapped 4.0L/AX-15/Dana 300, 4.88, AEV 3", LP9"/S88, Grizzly/Detroit, OTK steering, 35" muds... 84:1. 85 CJ-7: GM350/NV4500/D300, SOA on Wags, LP44/LP9", Aussies, 37" MT/Rs, Staun beadlocks, hi-steer, 110:1... in pieces.

03-02-2011, 04:29 PM	#11 (permalink)
jpfrk2001 New Beginnings Join Date: Sep 2007 Member # 99513 Location: On the move Posts: 4,243	I have the EXACT drivetrain combo and tire size on my YJ. Go 5.38's Thats what I run 2800 RPM and Im turning around 75 on the Hwy no problem __________________ My jeep is a hotrod! /forum/jeep-hardcore-tech/658004-going-against-odds.html NEW BEGINNINGS: /forum/general-4x4-discussion/971511-jealle-o-cigano.html

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03-01-2011, 06:49 PM	#3 (permalink)
POS YJ Registered User Join Date: Jan 2010 Member # 152085 Location: Chico, CA Posts: 77	You WILL NOT be happy with 4.88's!! Go 5.13's, if not deeper. The 4.0 will run fine at 3,000rpm on the freeway if that's what you're worried about.

03-01-2011, 09:52 PM	#4 (permalink)
Justdhutch Registered User Join Date: Aug 2010 Member # 166616 Location: Victorville, Ca Posts: 273	40's? I say 5.38's. That thing is gonna be a pig.

03-01-2011, 10:36 PM	#5 (permalink)
Ho Shorts Rock God Join Date: Feb 2008 Member # 109328 Location: Maryville, TN Posts: 1,574	I ran 4.88's with 38" on my XJ and it was on the borderline of being geared too high. 40's DEFINATELY go 5.13 if not 5.38

03-02-2011, 07:49 AM	#6 (permalink)
james@bluetorchfab Registered User Join Date: Aug 2008 Member # 118546 Location: NORWOOD, (BHAM) ALABAMA Posts: 711	My vote is 5.38's