Fuel Gauge and Automatic Transmission issues

[tekjones1983]

I've been driving the truck just fine then now the transmission is not wanting to stay in 4th gear or overdrive it just kicks in and out randomly and sometimes stay in 3 gear and goes back in but also when it messes up the fuel gauge is pegged over to full too

[SubGothius]

The combination of gauge and gear issues happening at the same time leads me to suspect a grounding issue, more specifically a short to ground somewhere in the wiring loom common to both components.

[tekjones1983]

That's what I was thinking too. Just where is the problem LoL but didn't act funny until I changed out the heater core and had to remove and put my dash back so I'm inspecting i might have pinched a wire or something like that wish me luck.

[tekjones1983]

Fixed the overdrive and fuel gauge issues I took the instrument cluster out and noticed the one of the connectors were not in all the way on the left bottom so I took all of them back out and reseated them. Yea so far so good. I did also check the wires by the computer and made sure the harness wasn't getting pinched and all connectors were all the way in because I did change out the fan assembly when I changed the heater core assembly at the same time. I checked under the driver side dash and pulled on the connectors and everything was good there and also checked under the truck and unhooked and reseated those connections beside the transmission and all grounds were tight.