has anybody had problems with their tachometer? mine will suddenly jump down to zero (causing the check engine and generator light to come on), and then my truck will kinda lurch....it kinda sounds like it's downshifting or kicking off overdrive? i'm not sure......it will also turn off cruise control if i'm using it. it crapped out on me today and i lost acceleration, so maybe it shifts into nuetral? somebody help me!

 

Sounds to me like an electrical problem. I would check the alternator and the batteries. Get a battery load tester and unhook the batteries and test them individually and see what they are. Battery testers are fairly easy to use. Before that start thge truck and use a voltmeter and check the alternator to see how much it is putting out. It needs to put out atleast 13.2 would be my best guess. if you have any q's just let me know. hope this helps you.

 

i just put two new batteries into the truck about a month or two ago, and it got a new generator last august.....the voltmeter in the cab registers at about 14, which it the norm. the truck is also making a god-awful groan at about 1000rpm, which it never did until last weekend when i had the front ball joints replaced.....maybe related, maybe not.

 

If it's not electrical, check the Crank Angle Sensor. It's behind the starter, and when they go bad, the tach fails and power drops off. One thing I didn't hear was that your truck starts up. When the crank angle sensor goes the truck won't start. It will crank but won't fire.
Check it out ahead of time as the CAS is about $90+ at the dealer and most won't return electrical components.