Recently the speedometer in my recently Muncie-equipped '70 stopped indicating. I bought the trans from an eBay vendor and rebuilt it with a kit from eBay as well. Initially I just reinserted the cable end hoping that it would cure the problem...it didn't. So my next step was to order a new (6-inch-longer) manual trans speedo cable, thinking that the over-stretched auto trans. cable was the culprit. Tore out half the interior to remove the old and install the new cable, putting a crack across my pristine 36-year-old dash pad in the process when it popped back into place-oops. Started the car, put it in gear, and about a second after the wheels began rolling I heard a barely perceptible 'pop' whereupon the speedo stopped indicating again. Jacked it back up, pulled the cable and gear out and found that the plastic gear was worn just enough to prevent it from meshing anymore with the drive gear (which has not moved on the output shaft and is properly centered in the tailshaft opening). I did a little research on the sizing of these gears and found that the toothed end of these gears come in two diameters-.820" and .870"(the one I have is .820"). It would at this point appear to me that eBay dude supplied me with a driven gear that was too small for the drive gear and the subsequent poor engagement caused it to eventually strip just enough to prevent further engagement, but it was a 19 tooth gear and was indicating pretty accurately in my 255/60-15 equipped car (the 'smallest' available .870" diameter gear is 22 teeth which would slow my speedo reading by about 14%). Can any of y'all enlighten me any further on this situation? At this point I've decided not to remove the transmission again; it's just too much !!*#@!? work to replace a speedo drive gear.

 

Are you trying to just run the cable directly to the trans? I thought the 4 spds had a 90 degee adapter then you put the speedo cable into that. Thats the way it was on my 73.

 

Yup.....and the cable also appears to be somewhat longer than it really needs to be, but cable length and/or the way it's plugged into the trans does not appear to be the problem. At this point my main concern is whether or not the .820" dia. driven gear is sufficiently large to work with the drive gear that I have or if there is a larger diameter drive gear available for use with the smaller gear.....does anybody know??