I can get pics of the install of the manual posi-lok kit if you want NAPA has them. but first I would highly recomend looking at rockauto.com the vac diaphram is 76 bucks plus shipping.

 

I just started having this same problem tonight with my '99. We've been getting pounded with snow the last couple weeks, and I've been pulling my gooseneck and skidsteer all over creation, most of the time in 4 hi, some fairly frequent but short uses of 4 low. Now all of a sudden no light and no 4wd.

Do '99 trucks have the CAD? I can't even crawl under there to look at anything, its caked up with some serious ice and road salt. Got to plow all day tomorrow too, this sucks! Anything I can check for that hasn't been mentioned in this thread, that is different on a '99?

 

it the same on the 99 have had mine freeze b4

 

Mine was a knocked off vacuum line. Big chunk of ice built up on the skid plate and pulled it loose. Got it working again but the dash light is not on now. It was on earlier, then I shifted from 4 high to low and it couldn't lock in, finally got it to lock in 4 high again after a lot of cussing and threats and I'm gonna leave it there til this storm ends.

The way the flimsy little vacuum hoses are routed down to the skid plate under the transfer case is dumb as hell. The skid plate acts like a flat shovel in heavy snow, and I'm amazed the lines stayed connected as long as they did. I am ordering the kit to eliminate the vacuum system. Good thread, thanks guys.

 

I just did a diagnosis on my 4X4 not working after reading this thread (good info) I did the following.
There were no lights on the dash with the key on and no motor running.
Probably not on the start up sequince...????
I got a vacum gauge took the two hoses off the actuator and stuck a hose on one of them started the truck cycled the 4x4 lever and I got vacum, I stuck the gauge on the other hose and got vacum in the opposite of moving the 4x4 lever.
Took the actuator off the axle 4 12mm bolts and blew thru the hoses on the actuator the arm moved but there is a leak in the diaghram, so I ordered a new actuator will come tomorrow and cure my problem this all took 15 minutes to figure out.
Hope this helps.
Grant.

 

Pulled this thread back up because I lost 4x4 also. Found the problem....lost vacumme.
But in the process I discovered I do not get a 4WD light when I turn the key on, but light IS working.
Can't remember if I ever did.... just always assumed so!
Does anyone else get 4WD light (with all the warning lights) when you turn the key.....pre start?

RJ

 

Tried several repairs to the place where the soft vacume lines meet the hardlines (on the passenger frame rail).
After splitting the plastic lines twice I did not have enough left to work with.... and every sleeve I tried would come loose after a day or two.
Long story short.... Entire vacumme line from the transfer case to the front axle is a one piece item. Single part #.
But, it's the first reasonably priced part from Dodge I've found. (under $40.00).
And it's the first R&R repair job on my 02 that was easier than it looked!
Put Zip ties on both ends of the vacumme lines to be sure they don't come loose again.
Probably overkill, since the factory lines lasted 200,000 miles and 7 yrs.

RJ

 

I just tried mine and I get no 4x4 light on the prestart. Only when it is engaged.

 

I forgot to post as well, on the 97 the 4X4 light also does not come on during the pre-start light test.