I'm new to this forum and I saw some underdrive pullies on American Trucks and I was wondering if they actually made a noticible difference? Has anyone put them on and if they have, are they at all worth it? Thanks!

 

I've had a UD crank pulley for over 2 yrs and I'm happy with it. At the time I added a few other mods so I can't say for sure just the pulley made a seat of the pants difference but you can see the diff on a dyno. Some have noticed the power steering needs more effort at very slow speeds. i.e parking but I have no regrets on installing mine.

 

I have an ASP underdrive pulley, and I like it.