Re-gearing

I couldn't seem to find any solid info on this topic for noobs so I thought I should ask these questions:

How difficult is it to re-gear an XJ?

How much would I expect to pay in parts AND/OR labor if I lack the skill to do them myself?

It makes sense that you must re-gear both the front and rear at the same time or Mr. Transfer case might not be your friend anymore right?

What are some good ratios to gear to If I want more performance, or mpg?

Is there some formula for determining how to return an XJ to stock "final drive ratios" (am I using that term right?) after putting on big tires?

Thanks for your input.

* couple hundred per axle for gears - I've seen R&P sets for anywhere from 150 to 300.
* anywhere from 250 to over a thousand per axle for lockers/autolockers (hey, if you're gonna pay to have the gears set, might as well right?)
* couple hundred per axle to get some guy to set them up for you (from what I've read.) You want a pro, or you might end up buying more gears... and having them set up again. Also, they'll charge more if you don't want to pull the axle out of the Jeep while they work on it, no one likes working under a rig.
* yes, you are 100% correct - either regear both at the same time, or pull your front DS to avoid ever forgetting and putting it in 4wd, or you WILL destroy gear sets, axle shafts, driveshafts, U-joints, transfer cases... whatever the weakest link(s) are, they will break very enthusiastically.

If you want to go back to stock drive ratio, what you want to do is this:
take your stock tire size and drive ratio (27.5 and 3.55 with stock tires and 4.0/aw4)
divide the stock ratio (3.55) by stock tire size (27.5) then multiply by the ACTUAL ROLLING DIAMETER of your actual tires (measure from flat ground to the center of the hub, multiply by two) to get what your "ideal stock ratio" would be. Pick the nearest ratio, you'll probably want to round up.

As for ratios, the lower the ratio (numeric, as in 3.55 or 4.10 or 5.38 etc) is, the more your acceleration and torque are going to suck, but the faster you will be able to go in a specific transmission gear before shifting. The higher the ratio is, the more torque you'll get and the more you'll be able to accelerate, but the slower you are going to be going when you shift to the next gear. Also, you will want to look into speedo gears if you go for any tire/gear ratio combo that doesn't give you approximately-stock performance, because it'll throw your speedo and odo all out of whack.

i'm going to have new gears installed when i put 35" tires on.. since i don't know much about proper backlash or have the tools i'll have the local off-road shop do it for me.

x2 on removing the axle if you're going to have someone re-gear it for you.

There was a post not to long ago with a chart of tire size/gears/mph/rpm that should help. This is a pretty good topic, as many of us discover we need to change gearing and repair diff's. It would be great to be able to set up your own gears and save $500+ on labor.

i use this simple formula i found on this forum somewheres..
(new tire size * stock gears) / stock tire size = new gear ratio

for instance.. my stock gears are 3.55 and i want to put 35" tires on.. stock xj tires are 27"?

35x3.55/27 = 4.60
so i'll be putting 4.56 gears in

Labor is usually $250 to $300 per axle around here. Gears and setup kits are ~$300. Lockers run the range from $200 to $900.

So I could walk into a shop, pay about a 1.5k and walk out with a regeard Jeep?

I just took mine in for 4.88's and a front true track. Unless things change before I get it back it's going to be 1750.00 for everything.

Not trying to be a jerk but I think there's a sticky at the top of the forum on axles/gearing that has a LOT of good info about choosing the best ratio.

I'm pricing this out too so this may help you.
At one shop I was quoted $1000 for re-gearing both axles (parts and labor).
At another local shop I was quoted $1900 parts and labor for ARB lockers front and rear and regearing to 4.56.

CherBear said:

So I could walk into a shop, pay about a 1.5k and walk out with a regeard Jeep?

Click to expand...

I would think that you could probably even find it for closer to $1100-$1200 parts and labor for both axles regeared, maybe less depending on the area.

XJJeepNewb said:

Not trying to be a jerk but I think there's a sticky at the top of the forum on axles/gearing that has a LOT of good info about choosing the best ratio.

I'm pricing this out too so this may help you.
At one shop I was quoted $1000 for re-gearing both axles (parts and labor).
At another local shop I was quoted $1900 parts and labor for ARB lockers front and rear and regearing to 4.56.

Click to expand...

Yea I wasn't trying to repost, I just thought some of that information should be compiled with pricing and more general information for Jeep noobs like myself.

def.ho said:

i use this simple formula i found on this forum somewheres..
(new tire size * stock gears) / stock tire size = new gear ratio

for instance.. my stock gears are 3.55 and i want to put 35" tires on.. stock xj tires are 27"?

35x3.55/27 = 4.60
so i'll be putting 4.56 gears in

Click to expand...

That is NOT gospel. It is a GUIDE.

It does not factor in other variables such as increased tire weight, increased rolling resistance, and increased drag. All of these increase the load on the engine.

For example, I know people who have 4.56s on 35s and say it's ok.

I run 4.88s on 35s and can't imagine a taller gear, it would be a dog around town. And I run a fairly light tire/wheel combo with no roof rack, stock bumpers, and usually no spare tire or tools on the road.

XJJeepNewb said:

At another local shop I was quoted $1900 parts and labor for ARB lockers front and rear and regearing to 4.56.

Click to expand...

That is an effing steal, if they'll honor that quote. ARBs go about $750 each, gearsets and install kits about $175 each. That pretty much equals your quote just for the parts.

You sure that quote included labor?

i was quoted 1500 to 1600 for my 8.25 and d30 geared to 4.56 and that was from 2 different places. that includes ring and pinions front carrier master rebuild kits as well. i am putting in a detroit but thats doesnt cost any extra and i already own it.

MoparManiac said:

That is NOT gospel. It is a GUIDE.

It does not factor in other variables such as increased tire weight, increased rolling resistance, and increased drag. All of these increase the load on the engine.

For example, I know people who have 4.56s on 35s and say it's ok.

I run 4.88s on 35s and can't imagine a taller gear, it would be a dog around town. And I run a fairly light tire/wheel combo with no roof rack, stock bumpers, and usually no spare tire or tools on the road.

Click to expand...

hmm. i appreciate the info; so are you saying 4.56s on 35's isn't so good? i have an automatic so the torque converter probably has yet another influence too.

XJJeepNewb said:

At another local shop I was quoted $1900 parts and labor for ARB lockers front and rear and regearing to 4.56.

Click to expand...

That's a bargain... sign up before they change their mind.

def.ho said:

hmm. i appreciate the info; so are you saying 4.56s on 35's isn't so good? i have an automatic so the torque converter probably has yet another influence too.

Click to expand...

I too have 4.88 on 35's and am happy. Don't think I would like 4.56's as much.

I'm running 4.56 with 35s in my rig, also with the AW4 trans. It's fine. Sure, it doesn't launch and smoke Civics like it did when it was stock, but it weighs considerably more now. Bumper, winch, rockers, rack, longarm, bellypan plus the considerable weight of the 35s and steelies. That's a lot of weight to get moving. I have a Detroit in the rear, so I can't spin the tires on pavement, but they spin real easy when it's wet.

It runs fine at speed, I can finally run in the fast lane on the highway again. Although the bigger hills slow me down a little. With 4.88s I'd have more power, but the rpms would be a bit higher than I like, even with the 0.75:1 overdrive gear. If you run into hills a lot on the highway, then 4.88 gears might be something to consider, but I can still hold 65mph in the hills.

CherBear said:

I couldn't seem to find any solid info on this topic for noobs so I thought I should ask these questions:

How difficult is it to re-gear an XJ?

How much would I expect to pay in parts AND/OR labor if I lack the skill to do them myself?

It makes sense that you must re-gear both the front and rear at the same time or Mr. Transfer case might not be your friend anymore right?

What are some good ratios to gear to If I want more performance, or mpg?

Is there some formula for determining how to return an XJ to stock "final drive ratios" (am I using that term right?) after putting on big tires?

Thanks for your input.

Click to expand...

How big do you plan on going?

ACK! I mistyped.....damn sorry guys, I meant to say that price was for AUSSIE lockers not ARB.
Yeah that would've been a GREAT deal! lol

Sorry for the confusion.