Need help diagnosing front end howl

[Muddybuddy]

Hi all, been a long time, but a good friend of mine has an ‘02 sport trac that he just bought and is trying to get it back on the road. The truck starts making a howling sound at about 5mph and gets louder as you accelerate. Does it in drive, coasting in neutral, and in reverse. However we noticed the sound stops when turning sharp left. the sound does not change when turning right. We checked the front diff, has plenty of fluid. Tires are pretty new (less than 5k miles), doesnt sound like tire noise.

-we removed the front driveshaft, no change. (Kept driveshaft off for all subsequent part changes)
-Replaced left wheel bearing, no noticeable change.
-Replaced lower ball joints (both sides), no change
-Replaced left CV shaft, no change.

At a loss right now. What are we missing? Where to go from here? Was thinking diff (bearings) but the fact that it goes away when turning left makes me think its not diff related.

was thinking about removing front diff all together. If we remove cv shafts and pull front diff, can the truck be driven? Obviously will only be 2wd, but he needs to get the truck back on the road asap.

any suggestions?

 

[koda2000]

Front diff bearings? Removing the DS doesn't stop the gears from turning.

 

[Muddybuddy]

Front diff bearings? Removing the DS doesn't stop the gears from turning.

The bearings meaning carrier bearings within the differential. Worn out bearings tend to make noise. But like I said, given that the noise stops when turning left, makes me think it may not be diff related, Because I dont think turning the wheels would have any impact on the diff.

I know removing the driveshaft does not stop the gears from spinning, it was to eliminate the driveshaft from being the culprit. In a previous explorer I owned, there were similar symptoms and it ended up being the front driveshaft.

we’ve been doing process of elimination to rule out what it could be. At this point, aside from going into the diff, not sure what else to look into.

 

[Elessar65]

Put the truck on jack stands, and make sure its solid. Run it while using a mechanics stechascope (or screwdriver/prybar held to the ear) to try and isolate the noise.

 

[donalds]

^^ rubber hose works great

 

[Muddybuddy]

Thanks guys, we’ll give that a shot. That was one of the next things we were thinking about doing but hadnt done it yet.

 

[toypaseo]

I would replace the right wheel bearing. Noise goes away turning left usually means the right one is bad.

It's a good idea to replace them both anyways...