CJ-7 Rear Popping Noise? - JeepForum.com
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post #1 of 6 Old 07-21-2009, 11:08 PM Thread Starter
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CJ-7 Rear Popping Noise?

My uncle asked me to post this with the hope someone might be able to help.....A few years back i had an automatic 1979 CJ7 and it ran great for years. But, out of nowhere it started to make a popping noise that sounded like it was coming from the rear. There hadn't been any recent events that would of caused it, like a wreck or getting stuck or anything, but it would only make the sound when I was backing up or making a sharp turn. One day I was towing it behind my truck with a tow bar and all of a sudden the front drive shaft came out and busted the transmission. There hasn't been a single mechanic or repair shop that has been able to figure out what happened or what the popping noise could of been. I purchased another 1979 CJ7 automatic and recently it has been making the same popping noise and I am concerned that the same thing may happen again. It is currently at the mechanics and has been for a few weeks now, and they too can't find what is causing this issue. If you have heard of this problem or ran into yourself, please let me know what you think or what you did to fix it. Sorry if i have left out any detail that would help, just let me know and i will try to reply back asap. This is just what he explained to me so i hope it's enough info.

Thank you in advance!

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post #2 of 6 Old 07-21-2009, 11:46 PM
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What transmission? transfercase? axles? gear ratios? motor?

Since you hear it more from the rear I would start with the rear axle and pop the diff off. Check the gears for abnormal wear or broken teeth. Check the fluid and make sure its still some what clean (not full of gunk). From there I would go to the rear drive shaft and make sure its in good shape. All joints are properly lubed, undamaged and work correctly.
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post #3 of 6 Old 07-21-2009, 11:59 PM Thread Starter
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I should be able to find out that info by tomorrow morning, but until then thanks for the start!
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post #4 of 6 Old 07-22-2009, 02:20 AM
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My friends had a 77 CJ-7 with automatic (quadratrac). Under load it would make a loud popping sound. It turned out that the transfer case chain was really stretched. Changing the chain made the sound go away.

I would imagine there must be a procedure for checking the chain for stretch without tearing the transferr case apart. Maybe someone who is familiar with the quadaratrac transfer case can chime in.
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post #5 of 6 Old 07-22-2009, 02:34 AM
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I did an inernet search and came up with this link to a quadratrac service manual section from an FSM. Look at the paragraph that addresses "stick-slip condition". Could this be what you're experiencing?

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post #6 of 6 Old 07-22-2009, 06:39 AM
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If you haven't serviced the QT, thats where I would start. Drain the fluid using the drain plug on the bottom. Then stick a screwdriver up thru the drain plug and apply pressure to the chain. You want no more the 1/2" of slack.

Also, are the axle gears the same.

1979 CJ7 - Propane powered 258/TH400/Q-trac- 2015 Project
1974 CJ5, 1980 Wagoner, 1976 CJ7
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