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Old 11-04-2013, 09:45 AM   #1
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Looking for Gear Ratio Swap Experiences

So back in 2012 (so long ago, I know) I bought my Sahara. I'll admit I didn't do the research I probably should have before buying her so I went with 3.21 gears. I realize now (and after a ton of research) that once you put 35" on it, performance suffers greatly. What I'm looking to do is upgrade to probably 3.73 or 4.10s.

tl;dr: Going from a factory built 3.21 setup to a 3.73/4.10 setup done by a shop or dealership. My questions are:

Have any of you done this type of swap?
What did it cost you?
I'm guessing no, but is it possible to do yourself?
Any suggestions or things to look for?

Also bonus internets to anyone that can link to all of the parts needed for the swap. I'd like to walk into the shop with the parts in hand so I only have to pay them for labor.

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Old 11-04-2013, 12:23 PM   #2
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I havent done it yet but would highly suggest letting the shop order the parts. Then if something happens you can make them stand behind their work.

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Old 11-04-2013, 01:03 PM   #3
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Also bonus internets to anyone that can link to all of the parts needed for the swap. I'd like to walk into the shop with the parts in hand so I only have to pay them for labor.
You can do this but if the swap fails (like if the ring/pinion backlash isn't correct and the diff smokes) you might be picking up the tab for parts.
This can be a little more involved than a lift, brakes, or exhaust and you want some form of warranty/protection against failure (and no finger pointing).

Edit: As long as I am spending your money, consider putting in a locker (in place of the factory carrier) since they will have it all apart.
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Old 11-04-2013, 06:12 PM   #4
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You can do this but if the swap fails (like if the ring/pinion backlash isn't correct and the diff smokes) you might be picking up the tab for parts.
This can be a little more involved than a lift, brakes, or exhaust and you want some form of warranty/protection against failure (and no finger pointing).

Edit: As long as I am spending your money, consider putting in a locker (in place of the factory carrier) since they will have it all apart.
X2. If you're paying to have it done- pay to have it all done, including parts ordering. Having your shop back the full install is WAY more important than the $100 you might save.
http://www.wranglerforum.com/f33/201...iy-223568.html
I'd suggest new bearings as well.
IMO on 3.73s; that's a lot of $$ to spend for not much change. I went 4.56s and very happy I did. Just search "3.21 gear" on the forum for any number of 5 gear related threads posted daily for more info.
This is old but the info. remains the same:
http://www.wranglerforum.com/f33/3-2...st-209000.html
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Old 11-04-2013, 06:20 PM   #5
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X2. If you're paying to have it done- pay to have it all done, including parts ordering. Having your shop back the full install is WAY more important than the $100 you might save.
http://www.wranglerforum.com/f33/201...iy-223568.html
I'd suggest new bearings as well.
IMO on 3.73s; that's a lot of $$ to spend for not much change. I went 4.56s and very happy I did. Just search "3.21 gear" on the forum for any number of 5 gear related threads posted daily for more info.
This is old but the info. remains the same:
http://www.wranglerforum.com/f33/3-2...st-209000.html
I concur. I originally planned on doing it myself so I bought the parts and then decided against it because it was my DD and I wanted it done fast. The gears had a problem after a few thousand miles, the shop guaranteed their work 100% but since I provided the parts it was up to me to contact the manufacturer. It became a pointing game and in the end agreed to split the cost including all shipping back and forth.
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Old 11-04-2013, 08:32 PM   #6
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Makes sense, I'll just ask what brand of parts they're getting then. I was leaning closer to 4.10s anyway. With 35s I'd like to be in the 'more than comfortable' range. Anybody know how much I should be looking at money wise?
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Old 11-04-2013, 08:36 PM   #7
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Makes sense, I'll just ask what brand of parts they're getting then. I was leaning closer to 4.10s anyway. With 35s I'd like to be in the 'more than comfortable' range. Anybody know how much I should be looking at money wise?

Why not just go with 4.56's.
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Old 11-04-2013, 09:19 PM   #8
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Call 4 wheel parts. Decent prices, decent work, full warranty. Locations around the country. At least you could get you a ball park. I had dual truetracs plus re gear. It was somewhere around $2k
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Old 11-04-2013, 10:09 PM   #9
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Why not just go with 4.56's.
After looking at all the stuff JeepHerz posted, I think that sounds like a good idea. Didn't realize how little of a difference from 3.21 to 3.73 or even 4.10 was. And god knows I don't care about gas mileage. So that seems like the move.

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Originally Posted by JKWrangler2012 View Post
Call 4 wheel parts. Decent prices, decent work, full warranty. Locations around the country. At least you could get you a ball park. I had dual truetracs plus re gear. It was somewhere around $2k
Looks like the closest 4 Wheel Parts shop is out near Pittsburgh or NC. I'm over in Philly. But I'll call around and see. There are a couple of specialty shops (Jeff Daniels Jeeps, The Jeep Shop, etc.) not too far from me. Although I've heard to maybe stay away from them just cause they might charge more cause they are a 'specialty' shop.
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Old 11-04-2013, 10:47 PM   #10
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Quote:
Originally Posted by Proxy404 View Post
After looking at all the stuff JeepHerz posted, I think that sounds like a good idea. Didn't realize how little of a difference from 3.21 to 3.73 or even 4.10 was. And god knows I don't care about gas mileage. So that seems like the move.



Looks like the closest 4 Wheel Parts shop is out near Pittsburgh or NC. I'm over in Philly. But I'll call around and see. There are a couple of specialty shops (Jeff Daniels Jeeps, The Jeep Shop, etc.) not too far from me. Although I've heard to maybe stay away from them just cause they might charge more cause they are a 'specialty' shop.
Generally a gear change will run you $1200-$2000. Ask the shop how many they do in a given month- and number of hours it will take. One guy here was told two days- ah, no thank you. (I doubt my 4 Wheel parts store does many at all- sure it varies.)
Ask them if 3.21s need a new carrier. If they say no- go somewhere else. There is a local shop by me that isn't a Jeep shop- but he does enough gears to know the answer...You also might want to try posting on your local forum page for referrals.
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Old 11-04-2013, 10:51 PM   #11
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I have the 3.21s and will be going to 4.88s shortly. The shop will order it all as advised by others. 3.21s are flat pathetic w/my auto, I HATE them.

I know, don't be a hater.
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Old 11-04-2013, 11:28 PM   #12
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I went from 3:21 to 4:56 when I upgraded from 33s to 35s. Had a shop do it as it's my only vehicle and couldn't afford downtime. It was the first mod I haven't done myself. If I had another vehicle I likely would have tried it myself.

I also toyed with the idea of lockers but didn't want to add the cost at that time but I at least had then throw and LSD in the rear. Only cost was the parts since they had the diff open anyways.

I drove with 35s and 3:21 for about a week and took a noticeable hit in mpg and that was just driving around town with moderate hills.

I recently reset my mpg gauge and drove for over a week trying to not be a lead foot and I'm getting almost 16 mpg. Was getting about 16.5 before the gear and tire change.

Cost here for the regear was $1900 plus the cost of the LSD which was about $450.
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Old 11-04-2013, 11:58 PM   #13
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I'm getting quoted $1,500.00 for the re-gear and carrier install. I bought a 2013 JKU sport in June with a dealer installed 2" lift and 35" tires. Of course they didn't change the gears. After a lot of research I decided to go with 4.88 gears. Less stress on the drivetrain and a good gear for 35-37" tires. I'm having the shop swap out the open diffs for ARB air lockers. I don't think it matters much who purchases the parts as long as you buy quality parts. I got Yukon high performance gears. Motive gear master install kit with Timkin bearings. Front axle tube seal. G2 diff covers. I would take the opportunity to get everything done at once. The shop shouldn't charge you any more money to swap out parts that are coming off. They have to take the axles out so why not have them put in tube seals. It's good insurance for little money and no labor cost. Sleeves and gussets are another one. But of course you'll have to pay for the welding.

I found a specialist shop with a solid reputation who does this every day. Check with some of the local Jeep clubs who they would recommend. Or better yet: who they wouldn't recommend.

Mines going in for surgery next Monday. Hopefully all goes well.
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Old 11-06-2013, 12:03 AM   #14
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Just had 4.10's put in my rear ASD to replace 3.21's and a Detroit Tru-Trac 4.10 put in the front. Went to drive out the door only to find my 2013 JKU woudn't upshift. Looks like there are programming issues with computer controlled stability, etc. from other threads here on WF, I found that one can only fix these programming issues with an AEV Procal module. Jeep/Chrysler dealers can't fix them either (or so I read.). So best check it out before you leap. I'm taking this info to my shop guys tomorrow to confirm.
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Old 11-06-2013, 12:10 AM   #15
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Just had 4.10's put in my rear ASD to replace 3.21's and a Detroit Tru-Trac 4.10 put in the front. Went to drive out the door only to find my 2013 JKU woudn't upshift. Looks like there are programming issues with computer controlled stability, etc. from other threads here on WF, I found that one can only fix these programming issues with an AEV Procal module. Jeep/Chrysler dealers can't fix them either (or so I read.). So best check it out before you leap. I'm taking this info to my shop guys tomorrow to confirm.
You will definitely need a programmer after a re-gear -- no question.

AEV, Superchips, Diablo... take your pick.

You also need it to properly program for larger tires, so buying one should be a no-brainer...

PS: Go with 4.56's or 4.88's. Anything less would be a huge waste of this golden opportunity to make your jeep drive even better.
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Old 11-06-2013, 06:06 PM   #16
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You will definitely need a programmer after a re-gear -- no question.

AEV, Superchips, Diablo... take your pick.

You also need it to properly program for larger tires, so buying one should be a no-brainer...

PS: Go with 4.56's or 4.88's. Anything less would be a huge waste of this golden opportunity to make your jeep drive even better.
I agree, just got a Superchip flashcal and changed a couple settings in mine, works like a charm and it's a must have if you plan on doing any moods to your jeep. Such as gears, bigger tires, lowering tire pressure etc.
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Old 11-07-2013, 09:46 AM   #17
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Will go with the Superchips Flashcal. Thx for the feedback!
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Old 11-07-2013, 10:05 AM   #18
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there is a lot of good information here.. and agree with most - going from a 3.21 to a 4.1 is pretty much a waste of money.

let me throw one more item for consideration into your axle rebuild here. unless i missed it, i didn't see anyone recommend reinforcing your axle. and while you're tearing it all down (replacing seals and bearings) there is no better time to insert some sleeves and c's or a truss.

welding the axle heats it significantly. we all know what concentrated heat can do to seals and bearings. just something to consider. you might add around 200 in parts (TeraFlex sleeve and c gusset kit) and around 200 in labor - for the welding - but there shouldn't be any additional labor. because -- if the shop is doing you right, they are completely rebuilding your axle.

food for thought.

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Old 11-07-2013, 02:21 PM   #19
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there is a lot of good information here.. and agree with most - going from a 3.21 to a 4.1 is pretty much a waste of money.

let me throw one more item for consideration into your axle rebuild here. unless i missed it, i didn't see anyone recommend reinforcing your axle. and while you're tearing it all down (replacing seals and bearings) there is no better time to insert some sleeves and c's or a truss.

welding the axle heats it significantly. we all know what concentrated heat can do to seals and bearings. just something to consider. you might add around 200 in parts (TeraFlex sleeve and c gusset kit) and around 200 in labor - for the welding - but there shouldn't be any additional labor. because -- if the shop is doing you right, they are completely rebuilding your axle.

food for thought.

Great advice! However, I would recommend the Artec JK Armor kits instead. (Not that your suggestion wouldn't work, as well) I just think the Artec kits are the most robust and effective reinforcements out there... and they're cheap!

Mine is getting Yukon 5.13s, the complete Artec D44 kit, and a RK HD Tie Rod next week...
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Old 12-23-2013, 09:52 PM   #20
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Another option for getting the re-gear done might be a junior college or technical school in your area. I had my front re-geared at the local junior college for free. The instructor supervised every time they worked on the Jeep and the main worker had been a mechanic in the Army but wanted the college paperwork to help get jobs. I had to leave it with them for several weeks, but it is not may daily driver so that was not a problem. Just throwing one more option out to save some $$$$.

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