I was driving across TN on I40 yesterday and had a strange occurrence. I was just west of Nashville doing about 75 mph. A small truck pulled over to pass someone. I had to slow down to keep off him. Evidently this pissed him off so he slowed to the same speed of the car he was passing. Before long there was a line behind me.

When I got the opportunity to pass him, I took it. When my truck hit 80, it started vibrating and the CEL was flashing. I slowed to 70 again and it continued for just a little. Then it smoothed out and ran as good as ever. A moment later the CEL stopped flashing went off. It ran fine the next 200 miles.

What was that?

 

without knowing what code turned the CEL on, it could have been any one of a thousand guesses.

 

Can a code be pulled without a light on?

 

Shudder may be a misfire for sure. Misfiring can also be due to fuel or lack thereof. Older trucks can get contaminates in the tank that slow or clog a fuel line. Injectors can also become clogged. Look at your service history if you can. Did you replace anything fuel or spark related? When have you last replaced a fuel filter?
Follow logical ideas and you will likely find the culprit. These trucks have amazing lifespans and issues are usually minor if you catch them early on. Code monitors are available that run on Bluetooth to an app on your phone. Thus allows you to catch real time diagnostics as they occur. I've been looking at a few myself, and they seem reasonable pricewise.

 

Throttle body position sensor is failing or a misfire on one of the 8 cylinders.