I'm hoping to gain some insights. The speedometer gauge has been jumping 10-20 mph, and sometimes while driving about 60 will hold steadily around 70. I installed a new cable without change then swapped in a spare gauge with no improvement. Cable routing is good with no sharp bends. Could the problem be in the driven gear that attaches to the transfer case? It's plastic teeth that go inside the transfer case actually look good, but can the female end that the cable fits into go bad?

 

If this is setup the same as my 87 Ranger the VSS for the CC plugs into the side of the trans/t-case & the speedo cable plugs into the VSS.

If your CC holds steady RPM's while the speedo is jumping all around the gear in the t-case is OK.

Strange problem.

 

That's a good point and yes the cruise control is steady. Is there any way the cable side of the gear could become stripped and cause the jumping I'm seeing in the gauge? From what I understand jumping is caused by the cable binding then snapping loose, so I wouldn't think so, but I've tried most everything else.


Do you guys typically grease a new cable before installing? I've experimented with a variety of lubricants over the years but haven't had good luck with any of them. Researching them online there seem to be as many opinions as posts. I did grease this new cable so assume that could be suspect too...

 

Yeah that's the same as my Ranger. I wonder if the VSS could be busted internally & not driving the cable as it should. Can you lockup the output side and see if the gear still spins?