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NP242 does the fulltime diff spin in 2wd

Desert4x4

NAXJA Forum User
Location
Phoenix
My transfer case seems to have developed an intermittent popping grinding noise. The noise goes away in 4x4 part time, but is noticeable in the other selections. I've installed a hub lockout kit, so I'm wondering if it's wearing out the Full-time diff, even though I'm not using full-time.
 
In any mode other than part time, the chain sprocket on the main shaft is free to spin about the main shaft on a set of needle bearings. With a non-disconnect axle, the front driveshaft back-drives the chain so those needle bearings are only seeing relative motion when cornering. With your lockout hubs, those bearings are now seeing significant relative motion between the main shaft and the chain sprocket. Pretty much any vehicle with lockout hubs is this way, so it's not typically an issue, but it may be your problem. I also recollect lock-out equipped vehicles using gear oil instead of ATF, but that may just be coincidental.

In 2wd, spin the driveshaft by hand. It may be necessary to unbolt the driveshaft to isolate to just the transfer case, but you may be able to feel it.

The roller bearings are #39: http://www.drivetrain.com/images/stories/product_imgs_large/242transcaseill_lg.jpg

Do you have a Tom Woods/Advanced Adapters HD SYE that replaces the main shaft? Having insufficient torque on the nut can cause issues like you describe. Ask me how I know... :anon:

With the OEM setup, the rear output bearing (#45) positions the main shaft fore-to-aft. If the bearing is wearing, the shaft could be moving fore-to-aft, which would be the same as moving the lever. See above comment about TW/AA HD SYE... You'll need to take the rear extension off to check the bearing, but its no big deal. Even replacing those needle bearings requires basic tools and one specific pair of snap rings pliers. An extra set of hands to put in the #42 snap ring all but a requirement.
 
The front output is always engaged, so if the front driveshaft is turning then the front output (and the chain) is turning too. The chain is attached to the sprocket on the main shaft, so that is also turning.

The differential planetary is only engaged in Full-Time mode. The differential is locked in the Part-Time modes, and completely disengaged in 2WD and Neutral (free spin on the needle bearings).

Mine makes a kind of chirpling sound from the gear noise in 2WD, goes away in Part-Time and Full-Time modes.

Popping would be something else, maybe a shift pad is worn out, or the differential teeth are lightly engaged, or something else.
 
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