I have a recently purchased 87 6.9 4x4 w/5speed and 3.55 rear. When I bought it the speedo didn't work so, without looking I bought a cable, it was cheep, when I went to pull the old one out I saw the gear in the tail housing was worn a bit in the middle of the gear. I called the dealer and asked for the part by application and he ask what color it was. It's "wine" colored, so I ordered it, put it in and drove to work the next day, which is 60miles. At first it bounced and so I thought that the cable and/or speedo head was sticky or maybe the cable was going out ( I never installed the new cable) so, it never accurately measured the correct speed (I know due to RPM levels how fast I'm going) it always seemed to be 10mph slower. By the time I got to work the odometer had only gone 45miles. On the way home it slowly went to nothing. Gear is worn out again. So, what's the problem here do I have the wrong gear on the cable or is the gear in the tail housing bad? Can you put different gears on the end of the cable to fit? I was thinking that maybe it had the wrong gear in there all along due to the fact that the gear is worn just a little bit in the middle?

Ken

 

The gear in mine is a pale green color and is right on with 33" tires and a 3.55 rear end gear.
The gear that the speedometer gear rides on only touches the center of the gear. You may have a worn gear in the tailshaft of the transmission.

I do not think it is a big deal to change, but mine is a 4x4 so my gear is in the transfer case.

 

Thanks Dave, I was hoping that wouldn't be the case of a worn gear in tail housing. Not hard to do just time I guess. But, just found a fuel leak at switching valve, hard to start now w/ -10 temps here and alt. isn't in the best shape either. So, I think I'll put the speedo on the back burner for now...

Ken