I have an 84 K10 with a TH400. My speedometer needle was bouncing around so I replaced the speedometer gear with a new one thinking that may fix the issue. Now my speedometer doesn't work at all, could it be because I don't have the speedometer gear lined up correctly with the gear that's inside the tail shaft? Or would there be another reason why the speedometer needle would stop working all together that I am missing.

Thanks for any and all input!

quote:

Originally posted by bcMOD3X3X:
I have an 84 K10 with a TH400. My speedometer needle was bouncing around so I replaced the speedometer gear with a new one thinking that may fix the issue. Now my speedometer doesn't work at all, could it be because I don't have the speedometer gear lined up correctly with the gear that's inside the tail shaft? Or would there be another reason why the speedometer needle would stop working all together that I am missing.

Thanks for any and all input!

My 1977 C10 Suburban has always done that. It requires taking the cable out through the top (speedometer end) and greasing it. Very rarely has mine stopped all together, but it has made wild 50 mph swings back and forth. I have to believe your issue is something similar. Others have told me they have run into the same thing with this vintage. Take care. Tom Worthington

Was the replacement gear the same as he original? On the plastic gears they apple core, the center of the gear wears away. The bouncing around is generally caused by a dry cable as Tom said. I took and old speedo gear housing and drilled and tapped it for a grease fItting so i could grease them from the bottom. Light grease and a little at a time works best. The best way is replace the cable and housing. The other way is disconnect the speedo cable from the speedo head and then pull the inner cable out and lube it with cable lube, graphite or light grease.

Graphite for cable lube

If you do decide to go the grease route, bicycle grease is a good light grease.