Need help swapping TO 2.72 gears - JeepForum.com
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post #1 of 11 Old 04-07-2018, 01:56 PM Thread Starter
nickgentleman
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Need help swapping TO 2.72 gears

I have stock axles front and rear with 3.31 gears. After my cummins swap, Iíd like to swap down to 2.72 gears. I think Iíll need a new carrier in the amc 20 to work with the 2.72 gears, but Iím not sure. Will I be able to swap the ring and pinions for both axles? Or will I need new carriers as well for both or just one?


1984 CJ7 Laredo - "Jenny"
Cummins 4BT
T19
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post #2 of 11 Old 04-07-2018, 02:29 PM
jeepwhore
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Like was mentioned in your other post, you'll only need a new carrier for the rear. But you can probably find a matching set of 2.72 axles for less than the cost of new gears and install kits.

'84 CJ-17: 17" stretch, locked Toy axles, 5.5" lift, FI, AX15, D300 w/twin sticks, boatsides & junk.
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post #3 of 11 Old 04-08-2018, 02:08 PM Thread Starter
nickgentleman
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Originally Posted by jeepwhore View Post
Like was mentioned in your other post, you'll only need a new carrier for the rear. But you can probably find a matching set of 2.72 axles for less than the cost of new gears and install kits.
Good point, Iím hoping I can find someone that doesnít need their old gears/carrier that will ship it to me for cheap. On a college student budget If you know anyone or are anyone PM me!

1984 CJ7 Laredo - "Jenny"
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post #4 of 11 Old 04-08-2018, 03:23 PM
only in a jeep cj
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Too bad your not closer. I have an extra set of widetrack 272s that we could just trade. Why go to all the trouble to set up gears when swapping the housing when it’s out is easier.

Ed
1975 CJ-6 1983 CJ-8
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post #5 of 11 Old 04-08-2018, 05:26 PM
cjoffroad
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There you go. only a 12 hour round trip drive and your good. I once drove from Norfolk to Cincinnati for a set of axles
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post #6 of 11 Old 04-08-2018, 07:42 PM
jp360cj
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Quote:
Originally Posted by nickgentleman View Post
Good point, Iím hoping I can find someone that doesnít need their old gears/carrier that will ship it to me for cheap. On a college student budget If you know anyone or are anyone PM me!


As mentioned, the cheapest and easiest way will be to find someone to swap complete axles


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77 CJ-7- AMC 360, Edelbrock cam, MC2100, Fenderwells, CJ T18/D20, Chevy D44/EB 9" rear, Trutrac f/r, 4.11, SOA, 1.25 lift shackles, 35x12.50 BFG KM2s, Shackle Reversal
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post #7 of 11 Old 04-08-2018, 10:27 PM
jeepdaddy2000
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Quote:
Originally Posted by nickgentleman View Post
I have stock axles front and rear with 3.31 gears. After my cummins swap, Iíd like to swap down to 2.72 gears. I think Iíll need a new carrier in the amc 20 to work with the 2.72 gears, but Iím not sure. Will I be able to swap the ring and pinions for both axles? Or will I need new carriers as well for both or just one?
Just out of curiosity:
What tire size are you running?
What RPM range are you looking at @60MPH?
What RPM's are you running now?

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post #8 of 11 Old 04-09-2018, 04:13 AM Thread Starter
nickgentleman
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Originally Posted by jeepdaddy2000 View Post
Just out of curiosity:
What tire size are you running?
What RPM range are you looking at @60MPH?
What RPM's are you running now?
Iím on 33s, maxing out speed at 55 (somewhere right around 2000 rpm), and not sure whatís being asked by the third question

1984 CJ7 Laredo - "Jenny"
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post #9 of 11 Old 04-09-2018, 04:21 AM Thread Starter
nickgentleman
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Originally Posted by only in a jeep cj View Post
Too bad your not closer. I have an extra set of widetrack 272s that we could just trade. Why go to all the trouble to set up gears when swapping the housing when itís out is easier.
Iíll tell ya what, if you have a garage we could swap them in, I might just take you up on that. I have friends at Florida State (Tallahassee) I could stop and stay with, and youíd only be about 3.5 hours from there.

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post #10 of 11 Old 04-09-2018, 05:43 AM
jeepdaddy2000
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I’m on 33s, maxing out speed at 55 (somewhere right around 2000 rpm), and not sure what’s being asked by the third question
Might get a tach and double check your actual running RPM's. Things like fans and engine noise can make the motor sound like it's running a lot afster than it actually is.
RPM's Seem a bit low for "maxing out". Many of these 4BT's should run up into the 2800-3000 range.
My only worry is 2.73's with 33" tires will drop your RPM's down so low that the rig becomes a slug.......
Just something to think on.....
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post #11 of 11 Old 04-09-2018, 06:17 AM
jp360cj
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Quote:
Originally Posted by jeepdaddy2000 View Post
Might get a tach and double check your actual running RPM's. Things like fans and engine noise can make the motor sound like it's running a lot afster than it actually is.
RPM's Seem a bit low for "maxing out". Many of these 4BT's should run up into the 2800-3000 range.
My only worry is 2.73's with 33" tires will drop your RPM's down so low that the rig becomes a slug.......
Just something to think on.....
Quote:
Originally Posted by nickgentleman View Post
Iím on 33s, maxing out speed at 55 (somewhere right around 2000 rpm), and not sure whatís being asked by the third question
What jeepdaddy said. Sounds like you are still doing a lot of guessing and assuming.

Get a tach so you exactly what RPM you are running.
Use GPS to verify speed.
Verify your current axle ratio.

Then you'll have the info to truly understand how big of a change you will be making. You may find you already have 2.72 gears. You may discover your current gears are lower than you think and you may be more satisfied with something other than 2.72s. You may discover the best course is an o/d transmission instead of a gear swap. You may find that your RPM's aren't as high as you think.

77 CJ-7- AMC 360, Edelbrock cam, MC2100, Fenderwells, CJ T18/D20, Chevy D44/EB 9" rear, Trutrac f/r, 4.11, SOA, 1.25 lift shackles, 35x12.50 BFG KM2s, Shackle Reversal
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