91 yj grinding noise

S

slaner75

New Member
Joined
May 19, 2023
Messages
9
Location
Ohio
Hello everyone I have been working on this jeep for a bit and can not figure out what this noise is. While driving between 30 and 45 mph there is an audible gringing noise somewhere either in transmission or transfercase it has 146k miles on it so I figured transmission so I rebuilt it replacing all the bearing, seals and syncros but it still does it. I removed the front drive shaft and it has seemed to stop the noise. Jeep has 4.0 and ax15 with np231 transfercase also the drive shaft ujoints are all new. Any help or ideas where I could look into next would be helpful.
Thanks for any info my problem.
 
Is your vacuum system still operable? Your front driveshaft should not be spinning while driving unless the front axle has been modified, so that raises the start of questions. Then based on that will affect what should be looked at next.
 
machoheadgames said:
Is your vacuum system still operable? Your front driveshaft should not be spinning while driving unless the front axle has been modified, so that raises the start of questions. Then based on that will affect what should be looked at next.
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I have not checked that yet I rebuilt the transfercase then the transmission still chasing this problem. The front end is my next project. Was hoping someone may have had the same issue to point me in the correct direction to fix it.
 
slaner75 said:
I have not checked that yet I rebuilt the transfercase then the transmission still chasing this problem. The front end is my next project. Was hoping someone may have had the same issue to point me in the correct direction to fix it.
Click to expand...
Well, kind of the chicken and the egg going on here. The front driveshaft should not be spinning, if the Jeep is all stock on the front axle. If the front axle vacuum coupling was deleted, then your front driveshaft should spin. The Front driveshaft spinning should not cause noise....if it does, then that would suggest something about the driveshaft spinning the transfer case is causing the noise.

You could also say the front axle has a problem (if the vacuum setup was deleted), but then the noise wouldn't go away when you pull the front shaft...so first thing I would do is see if the front axle has been converted to non-vacuum, and see if the front driveshaft spins.
 
machoheadgames said:
Well, kind of the chicken and the egg going on here. The front driveshaft should not be spinning, if the Jeep is all stock on the front axle. If the front axle vacuum coupling was deleted, then your front driveshaft should spin. The Front driveshaft spinning should not cause noise....if it does, then that would suggest something about the driveshaft spinning the transfer case is causing the noise.

You could also say the front axle has a problem (if the vacuum setup was deleted), but then the noise wouldn't go away when you pull the front shaft...so first thing I would do is see if the front axle has been converted to non-vacuum, and see if the front driveshaft spins.
Click to expand...
The vacuum actuator is still on the jeep if it works or not I am not sure. I will check that tomorrow.
 
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