Jeep TJ 4.0 popping out of 1st gear randomly

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andyfs

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morning all- could use some help.

Jeep Tj, 4.0, 155k miles.

Every now and then, what seems like completely randomly, while getting moving from a stop the car will pop out of first gear. itll make a pretty loud bang when it does it. This does not happen often, maybe once or twice a month. Generally I take my hand off the shifter when I start out, but sometimes when it happens my hand is on the shifter and i feel a good amount of vibration before it happens. I just put it back into gear and away it goes. really weird

Any thoughts? any diagnostics or things I should start with replacing to resolve it and start troubleshooting?
 
Duck Doctor said:
Profile shows 2000 so it's the AX15.
Click to expand...

🫢
2000'
New NVG-3550 manual transmission replaces the Aisin AX-15 transmission on the models with the 4.0L engine (includes synchromesh on reverse gear).

Get smart.gif
 
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andyfs said:
morning all- could use some help.

Jeep Tj, 4.0, 155k miles.

Every now and then, what seems like completely randomly, while getting moving from a stop the car will pop out of first gear. itll make a pretty loud bang when it does it. This does not happen often, maybe once or twice a month. Generally I take my hand off the shifter when I start out, but sometimes when it happens my hand is on the shifter and i feel a good amount of vibration before it happens. I just put it back into gear and away it goes. really weird

Any thoughts? any diagnostics or things I should start with replacing to resolve it and start troubleshooting?
Click to expand...

I agree with Boogieman. Here and then you're probably just getting it in the slot where it sorta rides the synchro and then pops out once power is ran through the gears. It happens. We get in a hurry at a light or aren't paying attention fully or whatever. You may want a different shift boot as well. That rubber gets old and stiff. My 2nd and 4th would pop out because I didn't fully push them in from a resistive shitty boot. The TC drop didn't help and was the main cause, but the old boot magnified it.
 
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Cooper Smith said:
I agree with Boogieman. Here and then you're probably just getting it in the slot where it sorta rides the synchro and then pops out once power is ran through the gears. It happens. We get in a hurry at a light or aren't paying attention fully or whatever. You may want a different shift boot as well. That rubber gets old and stiff. My 2nd and 4th would pop out because I didn't fully push them in from a resistive shitty boot.
Click to expand...
I ditched the thick rubber accordion boot in mine for a fake leather one ($12) that makes it shift much better, especially when temps are below freezing.
shift boot.jpg
 
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