You live in Denver ,Co I live at 8,500 ft plus in Bailey ,Co ...So tell me about hills again and 33's...LOL...you don't need 4.56 plus for 33's ,but if you want them that's your preference it's your Jeep you're entitled to build it any way you like ,but if I was asked is 4.10 sufficient for 33's I'd say yes and maybe 4.56 if planning 35's ...but I never recomemnd 4.56 plus in a d30 because the ...PINION GEAR...becomes the size of an acorn ,and prone to failure .

 

Is there a significant change in gas mileage with 33's and changing to 4.10 gears? Is it worth it to stay with 32" tires then?

I've been stuck on this question for a little while now....

 

Yes, and I wheel in Denver.

I agree that the pinion gets tiny, but I have not heard of it happen enough to have everyone avoid them and go to one tons.

Aside from the bigger rolling diameter, bigger tires add more weight. If you have armor, bumpers, roof rack, recovery gear, that is more weight your rig has to lug around where it affects power and mileage.

I don't know, but I was not happy w/my ratio. I had a weird size for 34s, but I think 4:88s was the way to go w/mine. And if I later went to 35s, perfect for an auto.

 

I would agree.

28's-3.55
31's-4.10
33's-4.56 (will work with 35's)
35's-4.88's
etc

Just my opinion. I like having passing power and the engine to be in the lower side of the power band when cruising at 25 or 75 mph...

you will use more gas with more throttle and 4.10's then less throttle and 4.56's. I don't See a point in buying 4.10's and doing all the work for a mediocre return.

I don't see how elevation has anything to do with tire height VS. gear ratio... height/ratio is the same no matter the elivation....

 

The elevation I live at was mentioned b/c performance on hills was mentioned and the person who mentioned lives in Denver stating he needs gears b/c he lives in Colorado ,and I live in Bailey ,Co which is a climb to ,8,500 ft from denver on 5-6-7 % grades and do it fine in my XJ

 

3rd gear is 1.1. i always drive in third almost every where i go unless i am out on the intersate and going to be running 70 or higher then i hit od

 

i made the swich when i changed to my dan 44's. 4.10 made a huge difference pushing the 33's. no longer under powered still crappy gas mileage tho

 

makes sense, i got that part. just wanted to clarify that gearing isn't different by elevation. IMO more gearing is always better (as long as your not over revving for long distances)

4.10's would help but aren't ideal. spend the money once

 

When I did Holy Cross last summer, doing Vail pass (10k ft), my engine kept having to go as low as 2nd gear. RPMs were up to 4k or more at times, and I was still barely chugging up the pass and holding up traffic. Had I had 4:88s (or even 4:56), I would've been able to hold 3rd for most of the time.

I thought my engine was going to blow up.

If you don't have these huge climbs, then 4:10s is good.

Like I said, it's a reasonable swap if you do the 8.8 and only have to regear the front which is how I did it, and saved $$. But mpg is going to suffer and power depending where you are.

 

How do you turn overdrive on in a 2000 xj?

 

Stick or manually do it

 

5th gear in a manual is OD. 4th, or D in an auto is OD.

 

I run 32" tires. I started out with my stock 3.55's and it sucked ****. Bad. I found stock front(250.00) and rear(200.00) axles out of xj's in junkyards that where geared to 4.10. Much better. I increased mpg from 10 to 13ish overall. Its actually pleasent to drive down the road now. But. 4.56 would be better. Just my .02.

 

I wanted to post on here my experience with this.

It's an anecdotal story, but I feel like most of the gearing arguments are. Here's the deal: I've been running 33" tires and stock 3.56 gears for the past 6 months. Combination of highway and street use for mileage purposes. I recently swapped axles and they have 4.10 gears in them. So I have heavier axles and a limited slip (this may play some part in mileage differences), but otherwise it's the same rig. I am in Arizona and don't drive many hills unless I'm wheeling. This may play some part in shifting to the final gear. With stock gears, I would still hit top gear on the freeways.

My mileage looked terrible (13mpg) with stock gears. But after adjusting for speedo errors, it's at 15mpg. Not great, but it's a Jeep so who's really complaining? Now, with 4.10's I'm very near stock gearing and after 3 tanks of gas I'm just under 15mpg after accounting for the very slight newer speedo error (it's a little less than stock ratio, but not 16% like the 3:56's were)

Considering how many people adamantly said that the Jeep 4.0 is certainly more efficient at 2300rpm and under it's potential when cruising at 1900 (like I have read from less than credible sources), I was led to believe that a) I would get better mileage with deeper gearing and b) 4.56 is the much better choice for 33's. I did add a heavier axle, but my mpg's actually stayed about the same. I don't necessarily think that either of these are true, especially for a DD.

This is my theory, it is entirely armchair engineer. Since it is hard to determine the credibility of statements in these threads, I have taken all sides with a grain of salt when making the following points:

1) While I know that people are well aware of this, you must consider your mileage after adjusting for the odometer error. The higher your relative gearing, the worse your mileage will look on paper. Simply swapping gears and reading the new distance traveled per tank does not count as getting better mpg's. The computer doesn't know the gearing in your axles or your tire size (unless you get a new speed sensor for the transfer case). I don't think most people are making this mistake, but I suspect it may happen from time to time.

2) I'm not sold on the 2300 rpm's being most efficient for best mpg. I get that this range is where the 4.0 is most efficient, but it's not as simple as that for mpgs. I'm assuming that 2300 is when the motor produces the most hp or torque given the amount of fuel. But if you're cruising, you don't need a huge amount of torque. You just need enough to keep the old jeepers in motion. When I cruise at 2300rpm at 50mph, the computer will switch the automatic up a gear. If the jeep were more efficient at that rpm, there would be no reason for the computer to shift to a lower rpm range. But the real time mpg readout and the computer both say it's more efficient. Either way, in my case it hardly made a snot of difference (with the caveats being that I've only tested for 3 tanks and I do have more weight in the axles now) for mpg's with gearing. And I think people who say it does may be falling to point (1)or live in very hilly areas where the stock gearing isn't enough to get into the final drive very often.

3) You do notice the switch from 3:56 to 4:10. It feels much better. If I were to have the choice of paying $2k to regear to 4:10 or stay with stock, I'd re-gear. It's a 15% better ratio and does not feel like it is wanting for power (unless you have high expectations) But...

4) I would still consider 4:56 for 33's heavily. I did 4:10's because they came with the axles. I think 4:88's would be too much for a DD, and openly call BS to anyone saying that it will get better mileage with 33's than 4:10's. I don't believe it. For crawling it would be awesome, but based on my experience no way no how would it get better mileage. I even think I would be getting worse mileage with 4:56's... but that's speculation.

5) I'm still not over the efficiency thing. If 2300 rpm's was the most efficient, why wouldn't the 4.0 idle at 2300? It's only efficient if you can use all of the torque/hp that it is making, otherwise it's just very efficiently running out of gas.

6) Re-gearing is awesome!

My little exploration of this is still happening, but I wanted to make note of these things for others who are going through the headache of deciding like I was (until an axle set decided for me ). It should be mentioned again that I live in a relatively flat area, drive an automatic, and have a relatively light rig (33x10.5 a/ts, low profile rear bumper, many plastics removed, no roof rack or huge front bumper, etc). Anything offensive was meant as humorous and I am no expert, this is just speculation on my personal experience.

 

I am running 4:56 in my jeep with a d30 and d44 33inch goodyears, arb lockers at both ends. lived in co most of my life and ran alot of trails and never broke any drivetrain parts. 4:56 will make a huge improvement in driveability and mpg. just my .02c