1990 Chevy 4 wheel drive blows fuse

[Topher.]

I have a 1990 Chevy truck old Scottsdale engine 7.4 liter. Four wheel drive suddenly stopped working after it had been working. Discovered blown fuse in dashboard. Replaced fuse and when engaging 4 wheel drive all lights in cab dim. Rechecked fuse. Hotter than a pistol. Complete automatic system according to manual. On a hunting trip and unable to get off Mountain without four wheel drive. Any help ASAP greatly appreciated.

[hunter4ever12]

Sounds like to me you have a short, only places this could happen are, your front differential actuator, your indicator switch on the transmission, or your switch on the transfer case. Most likely culprit though is the first one, especially if it's a stock actuator. If all else fails, unplug the actuator, and remove it... I sure hope you have tools with you, at least a crescent wrench, if not lesson learned..... Anyway if you can get it removed pry out/pull out the plunger as far as you can then thread it back in. Doing that will lock your front differential in all the time, so essentially whenever you shift the transfer case into 4 wheel drive you will have power to the front wheels. That way you can get off the mountain at least.

[Blue Bowtie]

That advice applies if the case is a Borg-Warner unit. However, depending upon the vehicle the case might be the NPG 208. Chances are that with the 454 it is a BW 4400 Series xfer case. If not, the actuator would still need to be removed, but the shift to 4H would be made by turning the shaft one click from the 2H position.

With either case, once off the hill and onto pavement, it would be best to manually set it back to 2H for the duration of your trip back to the ranch.

[Topher.]

thanks for all the help. problem ended up being the differential accuator shorted out.

it is the plunger style. was able to extend the plunger all the way out. used a tent peg head as a blocker to hold it open. put the rubber boot back on and installed. 4 wheel drive ran great. just reversed the repair after i got to the highway and drove home.