Anyone know what the speed sensor is for on the end of a speedo cable on an 88 F 150? What does it control?

 

One of many inputs for the computer. Do you8 have an electronic trans?

 

No it was a C6 auto but I changed to a NP435 and now just trying to figure out speed cable

 

do you have anti lock? some have a sensor in the rear end, some on the speedo cable

 

The sensor on the speedometer cable is generally only used on early trucks for speed/cruise control. Using the sensor in the rear end for speedometer started in 1992.

 

there is a anti lock sensor on the rear end, The truck is an 88 so the speed cable sensor would have been for cruise or computer?

 

Well, still not sure, There is a sensor on the Diff for Anti lock and it does not have cruise. Is it for the computer?

 

The sensor in the diff is just a rear wheel speed sensor, it was used in later years as the only input for all computerized functions. In yours you have one on the speedo cable as well, so it is an earlier setup. Yours was used for the ABS system if you have it. Since you have an actual physical cable to your speedo (I gather from your post) you have a mechanically driven speedometer unrelated to any sensors. The sensor at the end of the cable was used for your engine computer, to operate cruise control if you have it, and also for the computer to analyze vehicle speed in relation to engine load (load is determined by the throttle position sensor), this lets it do the math to operate the fuel injection ratios for different driving environments/conditions so it knows if you're coasting to cut back fuel, or if you have it mashed to dump in fuel & get out of harms way. This is where the increased mileage/economy & reliable performance of fuel injection is created. Those older systems with the sensor and cable are also ideal for old project vehicles, since they have the sender for the computer & still the cable to run the old school speedo, which is why I chose a 302 engine from an 88 bronco to set up in my 57 *****'s project. Later computers with electronic shift trannies also get upset if you change trannies since they can't sense it, earlier ones don't care.