Random Axles

[Flying Jester]

Well, If I'm swapping in an axle, and need to find what gear ratio is best, it will help if my amount of lift compared to my tire size is reasonable. I really have not dealt much with my jeep yet, I was told once to check the body to frame ground by a friend who is a mechanic (who really hates Jeeps, so he might not know as much as he acts like he does) so I figured it was a body-on-frame design. If not, aesthetics are nothing to me, so I can chop up the body to fit a tire that's a little to meaty.

So then, once I know if my plans for lift and tire size are solid, I can consider axle type and ratio.

I was looking at the GM 14 bolt because my jeep supposedly has a 4.10 axle ratio, and the blazer I'm looking at should be the same, so I could switch out only the back without grinding the gears. I live in Alaska, so I'd like the 4wd to be somewhat streetable.

 

[Ritter4.0]

If you are planning on axle swaps, you should go explore the Advanced Fab. section for about a week, at least. I learned a lot from it.

And a 14bolt is waaayy overkill for 31"s. People run those with 37"s+. Not to mention you want both front and rear axles to have nearly the same track width. A Chrysler 8.25 out of a 1997+ XJ will be a direct bolt in swap, and if out of a 4 banger should have 4.10's. 8.25's are also good to about 35"s when built up.

You can weld right? If not, then just forget about the swap, or find a welder to do it for you. Suspension parts do not work well with poor welds. I still need quite a bit of practice before I feel comfortable enough to drive on my welds everyday.


And lastly, explore the Advanced Fab section, its is much more friendly than Pirate4x4, but with about the same info.

 

[5-90]

Well, If I'm swapping in an axle, and need to find what gear ratio is best, it will help if my amount of lift compared to my tire size is reasonable. I really have not dealt much with my jeep yet, I was told once to check the body to frame ground by a friend who is a mechanic (who really hates Jeeps, so he might not know as much as he acts like he does) so I figured it was a body-on-frame design. If not, aesthetics are nothing to me, so I can chop up the body to fit a tire that's a little to meaty.

So then, once I know if my plans for lift and tire size are solid, I can consider axle type and ratio.

I was looking at the GM 14 bolt because my jeep supposedly has a 4.10 axle ratio, and the blazer I'm looking at should be the same, so I could switch out only the back without grinding the gears. I live in Alaska, so I'd like the 4wd to be somewhat streetable.

The only lift kits available for the XJ are suspension lifts. Being of unibody construction, the "frame" is welded to the "body" - and it would take an awful lot of fab work to lift the body.

And, gearing depends on a couple of primary factors - the rest would get plugged into the equation.

1) What is the anticipated/measured torque output curve of your engine?
2) Is this to be a daily driver, mixed-use rig, or off-road only?

We could probably address (2) first. If the rig is a DD, you want to gear it so that the ratio will complement the tyre size, and provide forward cruising speeds as close to the peak torque crankshaft speed as possible. If you're in between two ratios, you can probably go with the next one lower (numerically higher.)

If it's a mixed-use rig, it's going to depend on how "mixed" the use is. The more "DD-ish" the rig, the closer you want it to optimax gearing as above (either way, if you wish to change the tyre size permanently, you'll probably want to regear.)

If it's a crawl-only rig, then just go as low (numerically high) as you can go in both axles - since you're going to be all about getting over things. However, note that your on-pavement mileage will suck as a result.

It is the lack of information that generally makes it difficult to answer questions like this...

 

[Darky]

Try searching and reading around the forums a bit. There is a lot of info about everything you're asking. Check the stickies at the top of mod tech for threads discussing axle swaps, relative axle strengths, gear ratios, etc. You'll also find that you probably won't want to put any money into upgrading the 2.8.

EDIT: Also, I would highly recommend keeping the same bolt pattern front and rear. Do you really wanna carry two spares everywhere? I don't think there's a single truck out there with monster power that is purposely running different bolt pattern.

 

[Flying Jester]

I'me planning on driving it on the street about half the time. Would it really be so bad to have mismatched axle widths? It would be a hell of a lot easier to put in.

 

[arctycfox]

from the factory a lot of vehicles come narrower in the rear than the front, by anywhere from .5" to 1.75". This helps with turning radius. Switching to a wider rear with the stock front, especially as much as you're talking about, will destory your turning radius. I'd wager it might even add some serious stress to the front knuckles, but dunno, as never seen anyone WANT to do it, let alone ACTUALLY do it. For the amount of fab you're going to be into this anyways, might as well do both, and get strength front AND rear.


P.S. with 31's on a 14 bolt, your ground clearance is going to be rediculously low, about 3" I'd guess. Again though, never seen it done.

 

[kastein]

yeah... a 14 bolt with tires that small is gonna be a rock anchor for sure. Remember, a d35 cover is what, 9 or 10" tall? Just the ring gear is 10.5" tall on a 14 bolt and in stock form there's at least an inch or two of metal and air past that...

 

[Flying Jester]

Mostly my trails are abandoned roads in marshes and fields. More mellow than most, but way too austere for 2wd.

I'm not saying I want to have a bow-legged jeep with bastard spare tires and low ground clearance, but if that's what I can do, will it be better than stock? I was also planning on changing the front axle to a 1/2 or 3/4 ton ford front end, so wouldn't that help equalize the widths?

Would it be better to get a dana back end from the ford also? I can't get a nine inch, those are a hot item in Alaska, and my jeep-hating friend has snatched up all the good ford parts (he is a Ford-man).

 

[kastein]

You can run 31s on stock axles no problem. Heck, it sounds like you'd be fine with 31s on a d35 even, and I am an anti-d35 bigot.

Do that and you won't lose that ground clearance.

 

[Darky]

Find an XJ with an 8.25 in the back and swap that in. That will be plenty for 31s and austere abandoned roads.