I have a 93 toyota 4runner 3.0 with automatic, originally came with add but have aisin manual hubs on now the hubs have been locked in for a while now and i have no problems there however today when i put the transfer case into 4 hi i kicked in and works good no slipping but makes a horrible noise while driving down the road accelerating then I let off to coast it hums like there is no tomorrow, this all only happens noticably at a little higher speeds. sorry i can not more descriptive but if you guys could through a few ideas at me it would help, and if I am driving at 30 and i take it out of 4 the noise instantly goes away.

 

check u-joints on front drive shaft. And check cv joints on front axles.

 

I'm gonna take"Spindle bushings for 400 Alex!"...

 

thanks u-joints was the first thing I check they seemed ok, however I have no idea what spindal bushings are so I will have to look into that thank you.

 

ok i had a brain fart I was thinking spindle as some high tech piece in the diff or transfercase, not the spindle of the front wheels. However I do not believe that is the problem because the second I take it out of 4 wheel drive the whole problem goes away even with the hubs locked in or not.

 

I agree spindle bearings or cv shafts. You would not have sound because you are not applying torque to any of the parts to cause a grown.

 

While crawling around under there and greasing some things up i noticed that the front pinion has a little bit of play, I am able to slide the in and out just a little plus move it up and down a tad right at the diff. is this normal or possibly my problem. I did check the cv not ripped booots or play but they might still be bad.

 

It's not normal, pinion bearing is shot

 

would the bad bearing cause it to make all those noises only when in 4wd but not in 2wd. cause the driveshaft and every thing up there still spins in 2wd when i have my hubs locked in but there is no noise then. I figured the seal was bad and that is why it leaked lube but I did not know the bearing was bad. thanks