Million times it's been covered but I've been searching and reading for hours on this topic and either no one every fixes the problem or they never post the solution if they did it would help a lot of people and stop all the posts on this topic.
Mine jumps erratically some times more when it's cold and at 55 mph it jumps to 90 then back and forth if anyone has got a answer I'd really appreciate it
I had this problem and it was the cable. The issue was on the far end that hooks into the xfer case; the end kept getting chewed up. I had to replace it twice, but it's been working fine for 5+ years now.
'80 CJ7 - Gone but not forgotten
'83 CJ7 - Donkey
I had the bottom end of my cable round off, tried a coupole of the replacement inserts from the "HELP!" section at Auto Zone and Advance Auto, they bounced a lot. Bought a complete replacement from 4WDH, either Crown or O-A, still bounces. It will also go to different variations of inaccuracy, depending on the day. I have lubed it, trimmed it (The insert was too long for the housing it came with!) snugged it, loosened it, bent it, twisted it, lubed it with oil, graphite, light grease, lithium grease... still doesn't work right.. It is all the cable, since it only has issues until I mess ith the cable. I'd love to find an OEM cable, but I've only found the Jeep places that carry the O-A and Crown crap... all others just have the generic insert you trim to fit and crimp the end on...
Good luck. If you find anything, let us know!
1978 CJ5 5.0HO/T177/D300, '86 D30/D44 WT axles, 'glass body, 31x10.5 BFG A/T, TDK galv'd frame - DD and weekend toy