Hey folks, new to the forum. I have an 85 W-150 4x4 that was given to me by my late father. It was just his dump runner, but I am at least trying to breath some life back into the old gal. The last two issues I am dealing with is, the transfer case will slowly slip from 4 high back to 2 high without warning. Second is, there is an indicator light on the dash to show that the 4x4 is engaged, and it is showing no life. Any input? All fuses are intact and working. John

 

Are you sure it is the transfer case as that is not a common problem? If you have the vacuum actuated front axle, that system is more likely the culprit. The vacuum actuated system is also usually the source of the 4x4 light problem.

 

Interesting. I see this is a possibility, but would it also slip out if 4 low as well? As it is, I have no problems in 4 low, only in 4 high. Should I be chasing down a vacuum schematic for it as well?

 

New information always helps. If it is an axle motor problem I would think it would do it in low and high. The shifter for the transfer case has an adjustment procedure and that would be my first check with the info provided so far. I would also suspect the transfer case vacuum control switch if that adjustment is OK. I know that on my truck the vacuum switch on the transfer case does not engage properly due to something inside the case. The switch itself was OK because the problem persisted when I replaced the switch. The way I trouble shot this when mine was popping in and out of 4x4 was to bypass the switch by running a separate dedicated vacuum line to the axle vacuum motor and the problem cleared up. I have since pulled the switch from the T-case and made a manual vacuum motor control inside my truck using the old switch. I made it because it cost me nothing but there are store bought solutions out there.

I never found a schematic to cover this system. Vacuum is supplied to the vacuum accumulator ball located on the left side of the tranny and then to the T-case switch which has 4 ports. One port goes up to a filtered vacuum vent by the right fender under the hood. The other two ports go to the vacuum motor on the axle.

Continuity of the indicator switch on the axle can easily be tested for the light problem.

 

Thanks for all the input Seal. I will start with the linkage adjustment, and go from there. Enjoy your Thanksgiving