when crusing around 40-50Mph @ say 2000rpms on flat road my rpms will drop to 1000rpms for a second then back to 2000 then back again to 1000rmps.
this might go on for miles.
Full acceleration seems fine though. doesnt seem to happen with O/D off.
truck runs good otherwise
97 F150 4x4 rebuild trans ~ year ago,
4.2L V6 150,000mi


any thoughts?
thanks
Frank

 

is your O/D light flashing?

 

sounds more like the converter doesnt want to stay locked up..

 

no flashing o/d lights or other engine lights for that matter.
it really just a 500rmp flucuation-but annoying as hell
what needs replacing
thanks

 

x2

When they rebuilt the trans a year ago, did they put a new TC?

 

Does it sound like it's doing it or is your tach just doing it?