Finally Figured It Out & Fixed It!

[Fifty150hs]

I've had a "growling", vibrating noise up front for quite a while now. Not there when idling in park, just when in drive. Raised the idle speed to minimize it, but didn't get rid of it. Was never able to track it down, then someone on here mentioned motor mounts, so I replaced them. They definitely needed it, they were collapsed. Made things smooth, but still that noise. Then someone said the front drive shaft guibo could cause that kind of noise. So, I replaced that. Still had the noise.

Then I really started listening to it and trying to tie it to what was happening with the truck at the time. I noticed that it got worse when I'd turn the wheel when sitting at idle in gear. So, put a new PS pump in. It was leaking and needed to be replaced anyway. Still had the noise.

Then I remembered the last several times I had to loosen the belt tensioner (including to replace the pump) that it was pretty stiff and looking pretty worn out. So, I ordered new bearings and a new "spring" for it and rebuilt the assembly.

Voila! Problem solved! I was even able to drop the idle speed back down to normal. Wish I'd figured it out a long time ago. That noise was really annoying.