I need help with a screeching sound coming from both of the front hubs or possibly front diff while turning on my limited 98 4runner. It only happens in 4 wheel drive and is a sound that is a screeching and rubbing sound that happens at certain points of the wheel.

I recently put some downey 0-3" coil overs up front with a 1 inch PU block on top. I ran it at the full 4 inches for a while with a 1.25" diff drop. I felt a little vibration at times from the front so lowered the front lift and now am at 3 inches of lift with a 1.75 front diff drop. I also did the 231mm tundra brake upgrade just before, but seamed to have no problems after the upgrade.

I checked the diff fluid it seams fine a little dark but is full and now topped off.
I pulled the CV to check it and it seamed ok but at the bottom of my suspensioin travel it will not turn well so i adjusted the suspension to where there should not be a problem.

I shook the wheel and the bearings feel good and solid

The CV angle seem good to me.

I am stuck Help me out. I am headed from NorCal to Aspen in a couple of weeks and supposed to get the new tires on this weekend so if you have any ideas let me know.

 

CVs usually produce a knocking sound when they go bad, I've never heard them screech. How did the diff look when you pulled the CV? Since it doesn't seem to do it in 2wd, my guess would be something's up w/ the ADD/hubs (automatic diff disconnect).

Did you pull the other CV?

 

Thanks Brian. The diff looks fine no metal shavings in the fluid it was just a little murky I did not pull the other CV. And if it was the ADD what would i do to ensure it was before i start buying parts.

When i pulled the CV out i did my best to ensure it was still good but not totally sure how i would differentiate from a good one from a bad one apart from torn boots. Also i was a little surprised by how little the angle was that it could operate well at.

 

I know the ADD is vacuum actuated, but that's pretty much all I know about it. Maybe someone on here will provide more insight.

I was thinking ADD/hubs because aside from everything being under load while in 4wd, the the fact that the hubs are locked is really the only difference from 2wd (as far as spinning parts go).

It's hard to guess the nature of a sound over the internet so whatever it may be, test it or have it tested before you buy a new one.

 

Look for worn suspension components, check wheel bearings.....try to wiggle the cv joint nearest the hub back and forth.

Is the front driveshaft greased? If not, try that....

Look for evidence of wear on metal brake parts.

Maybe drain front diff, check fluid condition and look for flakes of metal.