Just bought an 85 f150 with 300 6cyl. The only gauge that worked was the fuel so after trying new sensors and attempting to rewire them I gave up and installed aftermarket mechanical gauges for oil and temp. Now I want to see what I can do about the speedometer. The gauge works when I spin it by hand. Where do I check the rest of the linkage? Also it seems to reach running temperature very fast. I replaced a badly clogged radiator and all the hoses and thermostat and flushed everything as good as I could without having to take everything apart. I haven't driven it very far for fear that it may overheat. Would advanced timing cause it to heat up faster? I am setting the timing with a light monday because it diesels occasionally when I shut it of.

 

I'm not entirely familiar with the '80-'86 gen but I'm assuming that the speedo is mechanical given that you were spinning it. There really isn't much to it then except for lighting wiring and the drive cable itself. Did you unplug the cable? Is it still laying somewhere behind the instrument cluster? A previous owner may have just simply unplugged it to hide its true mileage or it may be damaged. In any case, no real linkage other than the cable. I believe they are relatively inexpensive through LMC if you need to replace it with a new one or you can try a wrecking yard. The other end, by the way, is connected at the tail housing of the transmission and is driven by a little plastic gear inside. You can simply unscrew it and pull it straight out...the fun part is snaking it out and running the new one. Good luck!

Just a thought...you might try the wrecking yard for factory gauges too if you wish to switch back and the sensors didn't fix the problem.

 

If your truck came with gauges, any gauge cluster from 81-86 f-150, f-250, or Bronco, (I think the f-350 is also included in this list) will direct swap out with what you have, the gauges from a 80 series cluster as listed will swap into your cluster housing (unique wiring for 80, but, gauges were the same), if you need to replace the engine harness the same is true for the 81-86 series 6 cyl. engine
Hope this helps.

 

Thanks. I actually like the aftermarket gauges I got so no biggie there. The wiring to the factory gauges are shot there are breaks everywhere. The only one I can get a complete circuit on was the fuel. Where the speedo actually connected on the tranny is really what o wanted to know. I just replaced both calipers today because the brakes were dragging on the pass side. I have done a lot to this truck so far. The speedo is connected in the cab. I already had it of trying to fix the temp gauge. It doesn't overheat at all but it gets to running temp very fast, about 5 minutes. I was wondering if this is common with the 300.