Sinking Creek 4WD Association

So, should I swap down to 4.88s or to 5.13s when I swap my new axle in? Keep in mind I still DD this when I bring it down to school and have to drive to any wheeling trip. Think 5.13s would be slightly too low for the highway?

I have the 4.2 and ax-15 and 37 inch tires

id stick with 4.88s, your motor aint gonna like tryin to go down the highway at 4K rpms. just my $0.02

With 37s? I'd got 5.13s if not 5.38s. You can never go too low. Unless you're highway driving the hell out of it, which is the only time you need taller gears. Offroad and around town lower is better.

I ran 4.88s with a 4.0 and AW4 and wish I'd gone 5.38s/5.29s(was running a Toy rear axle). It's not that 4.88s was bad, because it wasn't, it's just that it would have been that much nicer to have a little more gear. That was with 35s. So with the manual trans and 37s, I would definately go lower than 4.88.

BlueDodgeRam wrote:id stick with 4.88s, your motor aint gonna like tryin to go down the highway at 4K rpms. just my $0.02

My jeep has never seen 4k rpms. It redlines at 4200

Right now it cruises at 75 at 1800 rpm lol

Arya Ebrahimi wrote:With 37s? I'd got 5.13s if not 5.38s. You can never go too low. Unless you're highway driving the hell out of it, which is the only time you need taller gears. Offroad and around town lower is better.

I ran 4.88s with a 4.0 and AW4 and wish I'd gone 5.38s/5.29s(was running a Toy rear axle). It's not that 4.88s was bad, because it wasn't, it's just that it would have been that much nicer to have a little more gear. That was with 35s. So with the manual trans and 37s, I would definately go lower than 4.88.

I only hit the highway to and from offroading and school so 5.13s sound better

Another vote for 5.13. If your junk has overdrive then you have no excuse not to go with 5.13. Trust me, you go 4.88's you'll be kicking yourself later.

Plus, 5.00 and below is where the cool kids play....

Fonger wrote:Another vote for 5.13. If your junk has overdrive then you have no excuse not to go with 5.13. Trust me, you go 4.88's you'll be kicking yourself later.

Plus, 5.00 and below is where the cool kids play....

I wanna be a cool kid. Guess I need to go with 5.13s now

what is your overdrive ratio? got a hp and torque curve for that motor?

Piney wrote:what is your overdrive ratio? got a hp and torque curve for that motor?

Horse power = nill

Torque = plenty

Overdrive = 0.79


edit: found the specs

112 hp at 3000 rpms (thats about as high as I take it)

210 ft lbs at 1800 rpm

The Jeep 6-cylinders have no problem singing along at 3k RPMs all day long. I used to run mine between 2700-3000 RPMs for 4-5 hours at a time running down the highway with no issues.

My 4.0 V6 specs at
160HP @ 4200rpm 220ft-lb @ 2400rpm

I did the majority of my highway driving with 4.56 gears, about 32" (measured size) tires, and 0.79:1 OD, and it was perfect scooting down the highway between 2500 and 3000 rpms and 70-80mph all day long. Mileage was good too. the giddy-up is all but gone with my 35's now.

in terms of final ratio, your 37's (assuming 36" actual size) with 5.13's would line up exactly with my 33's (actual 32") with 4.56's. I don't have experience with your motor, but from the specs and your qualitative description, it sounds like it does its best work at lower rpms than mine. I don't wanna say what you should run cause I have no actual experience with a rig like your's, but hopefully you can draw something from the comparison above.

Arya Ebrahimi wrote:The Jeep 6-cylinders have no problem singing along at 3k RPMs all day long. I used to run mine between 2700-3000 RPMs for 4-5 hours at a time running down the highway with no issues.

Was it a 4.2 or a 4.0?

4.0, but the basic design is the same. To the point that the heads can be swapped.

Arya Ebrahimi wrote:4.0, but the basic design is the same. To the point that the heads can be swapped.

Yea, I am gonna do that swap over the summer.

But I think the 4.0 has a much higher redline

Jwlman wrote:

Arya Ebrahimi wrote:4.0, but the basic design is the same. To the point that the heads can be swapped.

Yea, I am gonna do that swap over the summer.

But I think the 4.0 has a much higher redline

5kish