# Four wheel drive **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [December 2, 2008, 1:55am UTC](https://community.cartalk.com/t/four-wheel-drive/22808 "2008-12-02T01:55:09Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![summersk](https://avatars.discourse-cdn.com/v4/letter/s/f0a364/32.png) [@summersk](https://community.cartalk.com/u/summersk)\ **Post date:** [December 2, 2008, 1:55am UTC](https://community.cartalk.com/t/four-wheel-drive/22808/1 "2008-12-02T01:55:09Z")
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? ---
**Author:** ![MikeInNH](https://avatars.discourse-cdn.com/v4/letter/m/a587f6/32.png) [@MikeInNH](https://community.cartalk.com/u/MikeInNH)\ **Post date:** [December 2, 2008, 2:44am UTC](https://community.cartalk.com/t/four-wheel-drive/22808/2 "2008-12-02T02:44:29Z")
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. ---
**Author:** ![BustedKnuckles](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bustedknuckles/32/25_2.png) [@BustedKnuckles](https://community.cartalk.com/u/BustedKnuckles)\ **Post date:** [December 2, 2008, 3:05am UTC](https://community.cartalk.com/t/four-wheel-drive/22808/3 "2008-12-02T03:05:36Z")
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](http://dashboards.tv/images/rube-goldberg.jpg) Another Rube Goldberg inspired treat: