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AndyZJ

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Discussion starter · #1 ·
Now this is a 1999 Grand Cherokee with a 4.7L and NV247 tcase. We got this knocking sound like you were knocking on wood. Whenever the Jeep is in drive or reverse. I removed the front driveshaft and the noise went away. So naturally I replaced the front driveshaft, noise still there. I replaced the driver's side axle, noise still there. Replaced pinion bearings and tightened down pinion nut, noise still there. Checked all the spider gears and ring and pinion, no metal in case or fluid. I found a TSB about cutting a groove in the tcase output shaft nut to allow better airflow when the driveshaft is butted up to bolted down, noise was still there. I'm at my wits end other than replacing the whole front axle. When the vehicle is driving on the lift you can feel the knock in the front axle assembly, yet there is no damaged part when disassembled.

Anyone have a clue?
 
Discussion starter · #2 ·
Ok so yesterday I pulled the whole axle apart again and replaced the crush sleeve and outer pinion bearing. We are thinking of replacing the inner pinion bearing due to the pinion looking like its deflecting from the ring in the housing and causing gear knock. We'll see.
 
Sounds frustrating. I am getting knock in my front end as well when accelerating. I am going to try changing my u-joints and balancing it, and getting a new driveshaft if needed. I just had my front and rear diffs re-built (the rear whines like garbage, but the front is a driveshaft issue I think).
 
Discussion starter · #4 ·
I have a few contacts at Chrysler/Jeep dealers and after discussing with them all the new parts we threw at this front axle they decided this: According to one master tech this can be caused by what he calls a "hot tooth" on the ring gear. This tooth does not contact the pinion precisely and will knock when it rotates past like the same way you'd make a snap sound with your thumb and finger. Anyhoo, the fix was to basically install a new ring and pinion. Now here's the awesome part. My dad called my cousin who we bought the new front driveshaft from and he told us he had a friend with a 1999 Grand Cherokee parts vehicle he had (which was where the driveshaft originally came from) that he'd be willing to sell for $500. You can't even buy a wrecked WJ at the insurance auctions for that cheap so we jumped on that. So I worked half the day installing the whole front axle out of the other Jeep into the one we're fixing and problem solved. Plus now I have a WJ to pick from for my WJ. It was a good day all in all.
 
Now that is a deal, I am sure you will find $500 worth of parts from it...
 
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