[crgrissom]

Originally Posted by robncar

Do yourself a favor and listen to Jerry on this one. 4.88's with 33's and the 4-speed auto is the right combination.

Listen to these guys. I wish I could have gone lower than 4.88 for my 35's.

Chuck

[Lawrence]

I used to run 4.88s with my 35s and it was ok, 5.13s would have been better but the D30 doesn't allow for this. I now run 33s, and with the 4-speed auto it couldn't be any better, both on the highway and offroad. I usually drive 100+ miles to get to the trails and I don't have to turn the OD off anymore. Stick it in Drive until I get to the trail head.

[msavard]

anyone suggesting anything other than 488 has never driven 488s

[deltabravo]

Originally Posted by robncar

Do yourself a favor and listen to Jerry on this one. 4.88's with 33's and the 4-speed auto is the right combination.

what he said. I'm running 4.88s with 33x12.50x15 BFG MTs. Works well in my 4 speed Auto. On hills I still have to knock it out of overdrive, but I wouldn't want gears higher (4.56s) because then it would be really gutless. I also wouldn't want lower gears with 33s for highway driving. (65 mph+)

I initially thought I wanted 4.56s, but the shop I went to said "4.88s are the way to go for 33s".

By the way, the shop that did my gear swap was Nortridge4x4.com

[4xjeep]

not to steal the op's thread but what about 4.10's in a 3spd auto with 31's. is that ideal? i currently have 3.07's

[jeep rio]

Originally Posted by deltabravo

what he said. I'm running 4.88s with 33x12.50x15 BFG MTs. Works well in my 4 speed Auto. On hills I still have to knock it out of overdrive, but I wouldn't want gears higher (4.56s) because then it would be really gutless. I also wouldn't want lower gears with 33s for highway driving. (65 mph+)

I initially thought I wanted 4.56s, but the shop I went to said "4.88s are the way to go for 33s".

By the way, the shop that did my gear swap was Nortridge4x4.com

Just curious What Kind of RPMS are you pulling at say 65 or 70 mph?

[FanAholic]

what about gas mileage with a 488 regear? Should I expect it to stay the same get worse or better than 373?

[zband]

Originally Posted by FanAholic

what about gas mileage with a 488 regear? Should I expect it to stay the same get worse or better than 373?

This is the question thats difficult to answer perhaps because there are so many variables - I'm trying to learn as much as I can before making the plunge. The answer, I feel, lies in determining at what point is the 4.0 running the most efficiently (while cruising)? Is it 2000 or 2500 or even higher? Common sense would suggest to look at what the factory geared then with originally. But here's the problem - Jeep was not concerned much with fuel economy during the 97-02 years because they had a 3 spd auto (final drive ratio 1:1). So on the highway your jeep would be running near 3 grand ! So in 03 they switched to the 42rle - not sure if this was for fuel efficiency reasons or what, but at 70 I was spinning the engine at 2000. But the advertised EPA estimates stayed about the same (16/19). Despite this EPA claim I never managed to achieve 19 MPG.

City driving is another story here aerodynamics are not as significant so I figure 4.88 would be the clear choice.

So what burns more fuel while cruising on the highway forcing they engine to maintain 70 or less RPM's? I dont know.

[Roko]

Out of interest, I did an experiment the other weekend to see how much fuel savings I'd get driving "slow".. I did a 300 km drive at about 120-130 km/hr (which is the mid range speed of traffic on this highway) and used almost an entire tank of gas, since the tranny mostly stayed in third, and would not settle into overdrive. Doint it again at 110-120 km/hr, trying to keep it in OD as much as possible, I used up only about 2/3rds of what I'd used going faster.

I'm hoping that 4.88s might keep it in the ideal RPM range to stay in OD on highway, since I do a lot of several hour highway trips, including just to get to the trailhead. I guess I'll cross my fingers and wait and see. I wouldn't mind saving the gas.. Jeep's are definatley pigs on gas especially when you build them up, but that doesn't mean you can't try to optimize and make it "less bad" than it has to be.. :P

[Lawrence]

Originally Posted by jeep rio

Just curious What Kind of RPMS are you pulling at say 65 or 70 mph?

This is what I get with my 4-speed auto, 4.88s, and 33s:

OD ON
57 mph GPS - 2,000 rpms
62 mph GPS - 2,250 rpms
67 mph GPS - 2,350 rpms
71 mph GPS - 2,500 rpms
76 mph GPS - 2,650 rpms

OD OFF
58 mph GPS - 2,900 rpms
62 mph GPS - 3,150 rpms
68 mph GPS - 3,350 rpms
71 mph GPS - 3,650 rpms

[Jerry Bransford]

NICE RPMs Lawrence, I wish mine were like that.

[zband]

Lawrence - what are getting as MPG with your setup?

[Lawrence]

Originally Posted by Jerry Bransford

NICE RPMs Lawrence, I wish mine were like that.

4-speed baby… I think you need one of those

Originally Posted by zband

Lawrence - what are getting as MPG with your setup?

Truthfully, I have no idea. I didn’t care much about it before the gear/tire swap, and I still don’t care much about it. My TJ is not my DD, but with that said, if I really wanted MPG, I would have bought something else.

I used to run 35s with my 4.88s, and just going by the gas gauge and some trips I often take, it doesn’t seem that I am burning more gas with the 33s (read: I refuel at the same intervals). It is probably due to the fact that on grades, I am able to hold the speed nicely with the 33s instead of having to kick the OD off, something that frequently happened with the 35s.

To me, the ability to cruise at a favorable rpm range, and the fact that the TJ doesn’t downshift on long grades anymore, was more important than a 1 or 2 mpg hypothetical decrease. At those rpms, the engine runs much better, it pulls nicely, and the TJ is a whole lot of fun to drive.

For you SoCal residents, the kicker for me was the last time I went through the Cajon pass. The weather wasn’t so nice and the wind was incredibly strong, with wicked bursts. I was able to hold my speed and pass cars instead of having to pull into the slow lane and watch big rigs blow by me.

[hoseclamp]

I drove a '05 LJ Rube, stock with the auto, talk about laaaaaazy. ANy slight hill it would downshift, no acceleration in OD. It should come with 4.56's from the factory IMO. 4.88's are the lowest you can go, do the 4.88's, absolutely.

[robncar]

Originally Posted by Lawrence

...For you SoCal residents, the kicker for me was the last time I went through the Cajon pass. The weather wasn’t so nice and the wind was incredibly strong, with wicked bursts. I was able to hold my speed and pass cars instead of having to pull into the slow lane and watch big rigs blow by me.

Been there, done that.