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Four wheel drive

I have a Dodge Ram 1500 1997. My problem is four wheel drive on the truck and some one told me something about Rube Goldberg Vacuum servo/Switch set-up. What is that and where is it located at?

My 84 GMC S-15 had a vacuum actuated 4wd system (made by chryco). I wonder if it might be the same thing. The vacuum actuator was located in the engine compartment on the fender well.

Many trucks have servo switches, but Dodge uses the Rube Goldberg servo system. Under the dash, the button moves a switch, that drops a ball, that travels down a ramp to a bucket. The ball falls in the bucket, which tetters another lever that spins a fan. The wind creates a vacuum that actuates the 4WD servo, and kicks in 4WH.

Rube Goldberg was truly a master:
http://dashboards.tv/images/rube-goldberg.jpg

Another Rube Goldberg inspired treat: