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Unread 07-23-2013, 02:08 PM   #1
war6191
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Wide or narrow track question?

I think my 79 CJ 7 AMC 20 axle has been swapped at some point in its life to a wide track from the original narrow track.

How exactly do I determine this is the situation?. (I really would rather not have to pull an axle and measure it.) Is there an external measurement method or other thing a person can do. ?

I've heard you can visualize it by noting whether rear tires sit in further than the front, is this true. I do not use spacers.


thanks

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Unread 07-23-2013, 02:17 PM   #2
7CJ5White6
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no need to pull the axel. I'll go measure from one break caliber to the other and tell you what a narrow axel is and you can then measure yours and if its the same then you have a narrow.
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Unread 07-23-2013, 02:18 PM   #3
Renegade82
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You can measure externally from flange to flange but I don't have those numbers handy. It's something like 55" vs. 51" but that not exact. A search on "amc 20 narrow track vs wide track" should find it pretty quickly.
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Unread 07-23-2013, 04:26 PM   #4
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Narrow tracks measure 50.5 inches wheel to wheel. Wide tracks measure 54.5 inches wheel to wheel.
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Unread 07-23-2013, 05:54 PM   #5
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Quote:
Originally Posted by WindKnot View Post
Narrow track rear axles measure 50.5 inches wheel to wheel. Wide tracks measure 54.5 inches wheel to wheel.
Added just one small detail to that just in case someone is checking their front axle. Front CJ axles are wider (around 3") for both narrow and wide track.
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Unread 07-23-2013, 08:44 PM   #6
aggiejon
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Not meaning to hijack, but would there be any issues with leaving the narrow track front axle and the wide trac axle in the back, which should put the track width of the front and back within an inch of each other?

I have a set of WTs in the shop and NTs under the jeep. Would be an easy swap on the rear.
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Unread 07-23-2013, 09:16 PM   #7
WindKnot
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The front axles are wider for better handling. Reversing what the engineers did will cause all kinds of grief.

CSP is absolutely right. Good catch.
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Unread 07-23-2013, 09:32 PM   #8
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Quote:
Originally Posted by WindKnot View Post
The front axles are wider for better handling. Reversing what the engineers did will cause all kinds of grief.
The increased width of the front axle has nothing to do with handling per se. The reason for the extra width up front is to allow the front wheels to turn a little more before the tires make contact (rub) on the frame/springs (allows for tighter turning radius). Swapping to WT rear axle will not cause any handling problems (nor will it affect turning radius). Your Jeep will still drive down the road the same either way. If you have both WT front and rear axles available, I would swap both... it's not that difficult.
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Unread 07-23-2013, 09:38 PM   #9
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A narrower rear does allow for better tracking in turns, so yes, it does affect handling per se.

Jeep didn't go wider to allow for more room for the tires to turn tighter, they did it in reaction to panic about CJ handling from 60 minutes. Even then, the front remained wider than the rear axle.
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Unread 07-23-2013, 11:42 PM   #10
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Jeep (and many other manufacturers) have had front axles wider than the rear (long before 60 Minutes was ever on the air), for the expressed purpose of increasing wheel clearance at full lock steering.
The change you are referring to (that may have been in part due to the 60 Minutes story), was the change from Narrow Trac to Wide Trac. This was an increase in the width of both front and rear axles.
With the exception of some all wheel steer vehicles, and spooled differentials, I've fount the rear end usually follows the front (tracking) just fine (even with a rear end that is equal to or slightly wider than the front). But that's just been my experience, others may differ.
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Unread 07-24-2013, 07:52 AM   #11
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I was speaking directly to the change from narrow to wide regarding the 60 minutes story. I realize that both front and rear changed and pretty sure I've stated that more than once already in this thread.

In the end, the rear shouldn't be wider than the front. It will lead to understeer, which may not be perceptible in most driving conditions, but it's there and can show up in conditions when you least expect it (slick roads for example).
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Unread 07-24-2013, 08:44 AM   #12
WindKnot
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Quote:
Originally Posted by Spieg8 View Post
The increased width of the front axle has nothing to do with handling per se...
I've always considered steering as a part of handling. When you put a wider track on the rear without changing the front, you're altering the geometry of the vehicle.

Believe it or not, some engineer at the factory looked into the problem and came up with a solution. After he did he had to get it by the bean counters (especially at AMC) to put it into the design of the Jeep. If they could've saved a nickel per unit by making the front axle narrower, they would've done it. This is the company that used wire nuts and duct tape for splicing the electrical system during assembly.
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Unread 07-24-2013, 10:37 AM   #13
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Have you checked to make sure the front and rear have the same gear ratios? It they don't you will tear them up quick..
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Unread 07-24-2013, 05:09 PM   #14
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A "low tech" approach is to look how far the tire sticks out of the fenders. On the N/T, a factory-size tire will not stick out past the fenders (not flares). Before the W/T, a side-mounted spare was an option for a long time. A typical 31" tire will stick out just an inch or so on the N/T, while it will stick out 3-4" on the W/T.

There are lots of threads about the differences, but to me, I've always loved the look of a N/T, how the tires line up with the sides of the body. Makes for a beautiful profile. Whenever a modern JK, or TJ passes by to give me a way, my first thought it... geez, they do look dorky with the tires sticking out.
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Unread 07-24-2013, 05:58 PM   #15
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Quote:
Originally Posted by hp_lovecraft View Post

There are lots of threads about the differences, but to me, I've always loved the look of a N/T, how the tires line up with the sides of the body. Makes for a beautiful profile. Whenever a modern JK, or TJ passes by to give me a way, my first thought it... geez, they do look dorky with the tires sticking out.
AGREED!!!!

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