94 Jimmy 4x4 Problem

I have a 94 GMC Jimmy and since I bought it I noticed the 4x4 didn't work. Or so I thought. I tried engaging the 4x4 with the engine off, on, in park, neutral, drive, over drive and it never would engage. I just figured it was a problem in the transfer case. I bumped the 4HI today while rolling down the road and the 4x4 engaged. Later on I tried engaging it again while rolling down the road but it didnt engage. So can anyone tell me what my problem would be? Oh and another question Is the oil filter that is near the driver side headlight the oil filter or is it for the transfer case?

Oh and another question Is the oil filter that is near the driver side headlight the oil filter or is it for the transfer case?

That's your oil filter. It's mounted remotely so you don't rip it off on the trail :wink:

I bumped the 4HI today while rolling down the road and the 4x4 engaged. Later on I tried engaging it again while rolling down the road but it didnt engage.

I don't know if that's good or not... Did it grind or clash gears goin' into 4-way?

I didn't even KNOW you could DO that wile moving.