In the video, the engine RPM is
about 3000 at 30mph, 4000 at 40mph.
You truck’s probably like mine with 3.73 rear gears. I calculated a few numbers for what my, and thus your, engine RPM would (should) be at those speeds with an 4L60E transmission… and your engine RPM isn’t where I think it should be.
At 30mph, my engine would be at ~2150 in 2nd, ~4120 in 1st. Yours is around 3000.
I think your transmission is slipping.
The engine RPM flare-up around 22s in the video also suggests the transmission is slipping.
Whether the transmission’s behavior is related to the “car wash” or simply a coincidence I can’t say.
IMHO amount of slippage indicates the transmission is in need of professional attention.
Let’s see what others say
Maybe
@NickTransmissions or
@tayto will comment.