5:24 pm
Club Member
February 18, 2020
Offline
4 wd not engaging. Below is what i have checked
All tires off ground , in 4wd and in first gear engine off. Both tires spin front driveshaft, rear driveshaft just wiggles a little when front shaft moving
Does this prove that the vacuum system is good ? Also when shifting into 4 wd low
The gear ratio does change in rear tires
, i can climb a small hill and notice the difference than when in 2wd. Does that point to some problem in the transfer case ? there also is some rattling noise seemingly coming from the tc.
if tc is bad thinking of rebuilding or find used good unit. Looks like complete rebuild kit is about $225 or so.
any ideas ? Also does anyone have a transmission lift i could borrow? Anyone have a used tc fo sale ?
thanks for any info,
jim ruppel
Jim Ruppel
10:28 am
Club Trailmaster
March 13, 2015
Offline Your rig is a later YJ yeah? Without being there and seeing what you are doing I am going to have to infer some things. But you are likely to see the vacuum system fail 1000 times per 1 np231 failure so I would put money on the vacuum system or maybe the shift linkage.
Was the engine running when you shifted into 4-hi with all wheels off the ground? If it wasn't then there was no vacuum to lock up the CAD (center axle disconnect) in the front axle.
Based on you saying that 4-low is working with speed being greatly reduced (like top speed is cut by more than in half), then my guess is that there is an issue with the vacuum system on the front axle. Otherwise for you to have low range and no front shaft spinning would require a broken chain in the transfer case which I don't think is possible without the whole thing going boom.
Try these three tests:
-With the engine off and in 2wd, does the front driveshaft spin?
-Without turning on the engine, shift into 4wd and check the front driveshaft again
-And finally, run the engine and repeat the 4wd with all tires off the ground.
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