When your tach starts to fail, will the cruise control work properly? If no CC, the vehicle speed sensor (VSS) coul be faulty. A bad VSS might cause shifting problems, but I'm not sure about that. Hopefully, more experienced members can comment on this topic.

If the CC works without tach, then the tachometer might have some electrical of problem.

 

Honda Service just told me the problem is not trans. It is a bad ignition coil! It is located inside the distributer. $91.00 Part and $76.00 for labor. I'll buy the part and put in in myself!!! Apparently, if your tach starts doing wierd stuff or stops, it is the coil....

 

Correction!!! The coil is Not inside the distributor. It is external underneath the dist.. Engine is too hot to mess with now but it looks like the 10mm bolts that hold it on will be a bitch to get to..

 

Done Deal!! Coil fixed everything. Tach works and trans doesn't bump around anymore. Strange that an ignition coil will fix a tachometer!! I thought Nissans were wierd!!! I love this stuff.