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4WD disengagement problem

casm

NAXJA Forum User
Location
Oklahoma
Searched but didn't find an exact match for what I'm seeing here. Hopefully someone can shed some light on what I might be looking at.

2001 Sport, NP231, D30/35 front & rear.

Last night I hit a rock spill hard enough to shred the passenger rear tire and put a slow leak in the passenger front. At the time, I was in 4HI. Changed the blown tire (at midnight, in pouring rain), drove the 20 miles home, parked. Everything up until now felt OK.

Today I come out and get in the Jeep. Noticed something new and exciting: 4HI engages as per normal (driving on light mud), but doesn't disengage immediately when shifting back into 2HI. It takes about 300-400 yards for this to happen, during which time you can still feel the front axle pulling. When it does disengage, it does so with a fairly noticeable bang and a feeling like you've driven over a speed bump too fast. Note that the shift from 4HI to 2HI feels normal, it's just the disengagement of the axle that feels odd.

I haven't got under the Jeep to look for damage yet due to the weather, but is there anything obvious I should check for that might be causing this? I'm thinking it may be a vacuum problem, but would like to hear suggestions before getting my hands dirty.
 
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The spare is probably different size. If there is even a slight difference in circumference from one tire to another, the system will wind up the driveline in 4wd. Then when you go from 4 to 2wd the mode collar in the t-case doesn't want to slide out of 4. The shift fork is spring loaded, so when you move the lever, it can go to the 2 position w/out the fork actually moving. It is then the springs job to push the collar out of 4wd mode when the bind is released. Over enough distance the collar will eventually work its way out of 4wd. The bang you here is this happening while there is still torque between the frt. and rr. drivelines. The same can happen with a tire low.

Brian
 
explorer said:
The spare is probably different size. If there is even a slight difference in circumference from one tire to another, the system will wind up the driveline in 4wd.

Thanks for the suggestion on this - I checked the tire specs, and sure enough the spare (215/75R16) was slightly smaller than the other three (225/75R16). The new tires should be in tomorrow, so we'll see if that cures it - sounds like it most likely will.

Oh, and to elaborate on the damage: the front tire's fine, but the rim has a nasty bend in it that's causing the leak. As for the rear, three relatively minor bends on the outside, one really bad one on the inside (lousy weather meant that I didn't pay much attention when I changed it). Time for a set of steel rims, methinks.
 
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