I pressure washed the bottom of my truck and know when I drive it it feels loose and it try to pull it one way or the other I felt like I was sliding
22 year old vehicle of unknown mileage (per your post), unknown age and condition of tires.
Tires
Worn suspension
Brakes
Just take it to a qualified shop and have it diagnosed, $125 is better than having people online guess about a vehicle. All we know is the undercarriage clean.
2 Likes
My top of the head guess would be something involving the brakes but you need an actual mechanic with hands on the truck. Meanwhile, drive it carefully and as little as possible.
I wonder if you managed to force water past the steering rack bellows with the pressure washer?
1 Like
Check the bushings, ball joints and wheel bearings.
Don’t use a full high pressure spray under the car. It might take off the undercoating or paint also.
Then why do Car Washes offer what is called a ’ Belly Wash ’ so you can get the winter salt washed off the underside of your vehicle .
Did you do it in the driveway? Or on a lift?
Car washes don’t use pressure washers. It’s a little bit more delicate spray, don’t you think?
4 Likes
Even the ones that are using high pressure water aren’t putting out nearly the kind of water pressure you get at the tip of a pressure washer wand. That pressure drops very quickly with distance from the nozzle, first off. With my pressure washer on high with the highest pressure nozzle, if I hold it a couple of feet away from something it’ll knock the dirt off. If I hold it 2 inches away, it’ll strip paint off of metal, as I discovered when I pressure washed my wife’s fancy bird bath and got in trouble. 
And even the car washes that use pressurized water for the underbody spray probably aren’t putting out 4,000psi even right at the tip like a good pressure washer will.
2 Likes
A ruined wheel speed sensor can do that. Should cause a light on the dash though