Putting in 4WD when already stuck

[techno]

I know what you mean. Mine will on occasion take 2-3 seconds longer than usual to engage. The system works on vacuum pressure to move the ADD sleeve, and there are several electrical relays used to activate the vacuum system. Vacuum leaks are the most common cause of problems apparently. The only reasons I can think of would be a delay in getting vacuum pressure up to what it needs to be to overcome any friction resistance in the sleeve, combine that with aligning the splines and you might have a scenario where a delay occurrs.

 

[Even Steven]

I am not doubting anything you have said, but why does the 4WD often seem to take such a long period of time to engage in what I consider to be ideal conditions?

I try to plan ahead and engage the 4WD before I get into any trouble. I make certain that I am on a long stretch of straight road, traveling well under 60 mph, no curves or turns, no wheel spin, etc., and yet sometimes the 4WD light will continue to blink for what seems like an eternity before the 4WD locks up. Other times, it takes much less time.

I\'ve tried letting off the accelerator, braking, applying more throttle, keeping the throttle constant, and so forth, and it just seems like you never know when it\'s going to take a while to engage or engage quickly.

From my experience, the 4wd system will not engage if you try to turn it on while accelerating. Last winter I was driving up a mountain road that was getting more and more snowy as I got higher in elevation. I flipped the 4wd HI switch, and the light kept blinking for the longest time because I was accelerating the entire time to keep my momentum up the hill. Once I let off the gas and coasted for a few seconds, it engaged right away. I was curious about what had happened, so I tried it two more times with the same exact results. I came to the conclusion that the 4wd system will not engage under acceleration loads.

 

[boston_kevin]

I believe it says something about this in the manual... Accelerating or turning (tigher turns) will cause a delay in engaging the 4WD system because you don't want a load on the transfer case while it shifts and you don't want to take a chance no aligning the splines properly because your wheel is turned.

 

[TheBlueWave]

I like manual hubs on my old rigs, wonder if it would be a good idea to try a manual hub swap here. I've never fully trusted the old saying "trash behind the dash", I like the shifter with manual hubs better. Wonder if anyone will try a swap...