Truck sounds like a galloping horse...?

My friend and I changed out my thermostat today for the URD Performance thermostat. Everything went relatively smooth and only took us a little over an hour of actual work. After all was said and done, I started the truck up and almost immediately noticed a horse-galloping-on-pavement type sound coming from the front end. Does anyone have any idea as to what may have caused this or how to remedy? Any input is appreciated. Thanks!

 

Check fan clearance to fan shroud?

 

I thought I did this but it definitely won't hurt to check again! Thanks!
But it didn't hit the shroud when we spun it by hand. It seemed the fan was completely clear

I...I think I love you

 

Morning bump

 

If the fan pulley went back on crooked somehow, spinning the fan by hand wouldn't cause a problem. Only when running would it contact the shroud.

 

We didn't touch any pulleys in this install. We only pulled the rear radiator and fan shroud..

 

Moving the fan shroud may have created a clearance problem as the engine torques on motor mounts.

Otherwise have you been hauling any hay recently?

 

Whatever the issue was, it resolved itself

 

Hmm. Wonder if it could have been air in the coolant system?

 

Anything is possible haha

 

Dude, he's holding his sunglasses and wearing them at the same time. How did the artist not catch that?

We all know he pulls his shades off when he's saying something cool....

 

It is supposed to make fun of the excessive use of the shades in the show thus he has them on already cause he's so cool he's cool. Its recursion.