Truck slowed down fast and lack of power

[am-radio]

I have the Denali with the 5.3 V8. My wife was driving today and had the cruise on at 115 km/hr. She tapped the brake pedal to shut of the cruise to merge off the highway. He said the truck slowed down fast on its own to 85 Km/hr. (like she was braking the entire time, but her foot wasn't on the pedal). When she tried to accelerate it had very little power. She said the engine sounded funny. I don't know what that means. The gauges remained normal she said and no check engine light came on. She was about to pull over and everything went back to normal. It's been fine all day after this happened this morning. Sounds like electronic issues, but I'm asking the forum for their expertise, knowledge or suggestions.

 

[CaptainXL]

Sounds like a lockup issue with the torque converter or brake issue. But hard to say.

I would service the trans fluid and filter asap as a precaution if it hasn't been regularly done. Check the fluid level and condition in the mean time.

But other than that without any code I would have no further ideas. Intermittent issues can be difficult to solve until they become chronic.

 

[am-radio]

The transmission level is normal. Fluids were changed at 100,000 km and I have 155,000 km now. Changing all fluids before summer and the spark plugs.

Will the dorman 265811 deep transmission pan with drain plug fit the 5.3 V8? I see many have installed it on their 4.2 I6. I hate not having a drain plug.