This started happening this morning on the highway going 65 mph. The RPM hand started to jump between 2400 and 2900, inconsistently. I did not notice any change in acceleration or idle or speed. It just suddenly started the jumping. After slowing down to 55 the rpm hand came down to 2000 rpm and settled down. I have seen speedo jumping in other vehicles before, but not the rpm hand. On a cold idle situation the hand jumps between 600 and 400 rpm. It's like seeing a clock (sec) hand going clock and counter clock wise at the same time.
Mine did this and it turned out the cable linkage was loose. Check the cable linkage near the xfer case under the truck. Check to see if everything is tight.
airlaird
Mine did this and it turned out the cable linkage was loose. Check the cable linkage near the xfer case under the truck. Check to see if everything is tight.
airlaird
You say under the truck? I purchased and mounted new tires on my rig this morning - local indie tire/brake shop - the tech guy shoved a floor jack under there - nothing major but I noticed it took a few tries to find the right spot for the jack. Up, old tire off, new tire on, down. Fronts and backs. A mile down the road later, my tach is twitching while I'm sitting at a red light - idling fine. This is the very first time the twitchy tach has occured and I've searched and discovered I'm not alone. ps - weather was very mild in Orlando today - mid to upper 60's, dry, moderate humidity.
Mine did this and it turned out the cable linkage was loose. Check the cable linkage near the xfer case under the truck. Check to see if everything is tight.
airlaird
I could be wrong, but doesn't the factory tach usually gets it's signal from the ecu which in terms gets signal from coil/ignitor? In the past when we had tach issues, they're usually electrical issues, most of the time being a bad/loose ground somewhere, two being alternator. GL
