Filling up the truck the gauge would read full. After driving (hwy) the gauge would dip. At just about the full line the gauge nose dived to E. Filling up again brought it to above the full line again. Funny the fuel low light didnt come on. Anyone have any ideas?

First, do you have the SR5 Gauges (w/Tach) or the standard cluster?

The most likely thing I would think would be an electrical problem, either a loose connection somewhere between the fuel sender and the gauge, or someplace where the insulation has worn away and is intermittenly grounding to something.

Did this happen suddenly or over time? If it happened suddenly I would sure think wiring, but I suppose your in-tank sender could have gone south too.

When I got my truck a little over a year ago, the fuel gage didn't work at all. After a few offroading trips, it started to work sporadically (probably something in the sending unit got jarred free), but maybe for only the first 25-30 miles. Then it would just start jumping all over the place, until about another 30 miles later-- it goes back to showing empty. I've done several searches on this, and it seems to be a common problem only solved by dropping the tank and replacing the sending unit. It's really not worth it to me right now to do all that-- I just fill up every 200 miles.

At least you know your gauge works-- it's just not getting good information from the sending unit. Could also be a wiring problem like stock87 said.

It is the SR5 guages. It just happened out of the blue. Im searching for loose/damage wiring right now. I filled up again (every 200 miles) and it went to the full mark and worked for about 62 miles then would intermittently dip then come up. Im thinking sendig unit in the tank at this point. I fill up almost once a day since i use my truck for work too. If any of you have replaced your in tank fuel level sensor who much was the part?
And thanks for the replies!

Let us know if the sender fixes it, I'm having a problem with my swapped in cluster right now where it reads fairly accurate for about that many miles, then reads empty by half a tank.

My 1987 4Runner.... Fill it up, then when it goes to about 1/2, it just dips straight to E.

(I love freaking passengers out with it though) Nice to be in the middle of the Rubicon reading E.......with no extra gas..........HA HA

Let me know if someone fixes it.