[paashla]

In the haynes manual it talks about differentials and states this about both Command-trac & Selec-trac systems - "each system (except for later Selec-trac equipped vehicles) has a front axle disconnect feature which disengages the right front axle via a splined shift collar which joins the right-intermediate axle with the outer axle. The system is controlled by a vacuum motor and shift fork...... When disengaged,the differintial is allowed to free wheel instead of turning the ring gear, pinion and frront drive shaft, thereby saving unnecessary wear on these components during two wheel drive operation " My question is, does anyone know what year the company decided that the Selec-tracs didn't need this feature anymore and why? I have an '01 WJ that the front driveshaft moves any time the vehicle moves and I was wondering if the "whirring" noise I hear when driving down the road is related to this as just a "nature of ther beast".

[comptiger5000]

AFAIK, only pre-91 XJs had this feature. I don't think any ZJs had vacuum disconnects, and WJs definitely didn't.

[StrokedWJ]

I'm pretty sure you're referring to the old HP D30's which had the vacuum disconnect for the passenger shaft. The system was phased out due to a lack of reliability with the vacuum disconnect system. The HP D30's were used in YJ's and XJ's.

That is the only problem I have with Haynes manuals, they're very generic and may or may not be correct for your specific vehicle.