Questions and Answers

Cherokee Has Three Wheel Drive Q. I am the owner of a 1991 Jeep Cherokee Limited with a 4.0 litre inline six, fuel injection, and a Selec-Trac transfer case with 157,000 miles. The transfer case has 2WD, 4x4 part-time, 4x4 full-time, neutral, and 4x4 low positions. The vehicle receives some off-road use, mostly in mud or gravel, and I recently became stuck in relatively shallow mud I didn't feel should be a problem.

In the process of attempting to free the Jeep, I noticed one front wheel was spinning while the other was stationary in both the 4x4 part-time and low-range. I would expect this type of slip in the rear differential, which I know is open. However I thought the Selec-Trac was equipped with a vacuum actuated front differential lock, and that this difference in rotational speed should be impossible were the lock working correctly. Is this four wheel drive system equipped with such a lock, or was I mistaken? If the lock is present, what are the repair options I should look at?

Thank you in advance for your time,
Mike

A. When the front differential is locked, both axles have to turn. And since one wheel is turning, it seems the differential is locking. The problem is more likely with the locking hub at the wheel itself. If I remember correctly, it has vacuum actuated automatic locking hubs. I would check the vacuum supply and lines to the hub. If that is okay, you will need to take the hub apart to see what is wrong.

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