Ok, 1990 4runner with ADD front hubs, the front of the diff says to use 75w-90 hypoid gear oil. I went out and bought mobile one gear oil that fit the specified criteria. NOw when i drive it in two wheel drive i hear a hum/grinding? sound that vibrates my floor slightly. I engage 4wd and keep driving and the hum sound goes away or may come on and off but only briefly. When I put it back in 2wd the hum comes back. I originally thought it was cavitation in the PS pump, due to lack of fluid, because I have a leak, but yet the sound of the PS noise is a constant hum that doesn't fluctuate with speed. This new noise will increase and decrease directly with with my vehicles speed.



I dunno maybe should i try a heavier weight oil. Oh and yes I put in the correct ammount.

 

Did the vacuum lines to the actuator become disconnected somehow?

I don't think a heavier weight is going to solve the problem. Don't know what that problem is, but still. I'd think a heavier weight oil would make it worse. Heavy oils are harder to push around. I know when I put heavier Mobil 1 in my motor it didn't like it so much. Not as much as others of supposed equivalent weight but different brand. The motor seems a bit noisier and more sluggish.

 

Oh crap, What's this? I didnt mess with any vaccuum lines. I just took out the fill plug, removed the drain plug, let it drain then then plug it up and filled it then rocked it back and forth in 4hi/2hi. I am thinking right now that I should ave done something that I didnt do.

 

you 100% sure you filled it all the way? should just barely drip out of the fill hole when cold.

 

yes, positive... I opened up another bottle to put more in just to see it drip for sure. then let it it stop dripping

 

could it be a coincidental noise that is actually something else, like a wheel bearing or something that just started to act up that night..... ?

 

absolutely. as long as the oil is good you should be fine. jack up the front and and try spinning the tires and check for any issues. you may of may not be able to notice it with no load.

 

right on, well I am off now to go brave th cold and get this thing up and start looking around to see if I can't find anything lse that will help in giving yall more info to help deduce the problem.

 

Oh...there's some vacuum lines....two....that go to the ADD actuator. They run down from the engine bay and across the top of the diff. They're quite visible. I just wondered if they got knocked loose during the process. Then, the 4wd wouldn't disengage. If they're still intact, don't worry about it.

It could be something coincidental. I was wondering about a u-joint or cv axle.

Good luck!

 

I'm with MMA Alex, check your wheel bearings. mine went and i didnt know because of the xtreme off road tires i had on.(Pro Comp Xterrain). so i would check them out before it gets really bad. even though it is a Toyota's REAR wheel bearings that go first.

 

Why does everyone think that Mobil One is going to make everything work better or last longer?

 

i just used it because that is what the mechanic I bought it from had been using in it, so I just stuck with what he was using. I bout puked when I actually paid for that expensive junk.

Update: Yes the noise goes away when i 4wd and then comes back on once in 2wd again.

How would I be able to tell if it was wheelbearing or cv axle. The boots are all in good shape. I saw where jim rockford on here replaced some brass rings that apparently wear out , but i dont believe his was a 2nd gen 4runner. Wold there be the same setup in the tacomas or 3rd gens?

 

i jacked up the front and spun both wheels and couldnt hear anything out of the ordinary. double checked the diff oil and vacuum connections and they are fine. I grabbed the bar from diff to the inner cv's and there wasn't any play with it.

 

Maybe another solution to troubleshooting this problem would be to buy a powerball lotto ticket and cross my fingers for SAS money and then.... bickety bamm problem solved

 

with the wheel off the ground take a hold at 3o'clock and 9o'clock and try to wiggle. it should have almost no play. if it does the wheel bearings should be looked at.

 

whens the last time you greased your drive shafts and what not

 

end of december

 

anybody know any parts numbers i would need to replace wheel bearings?

 

It's 6 and 12.

 

its both. 6 and 12 will also wiggle if theres a ball joint problem. with a wheel bearing issue it will technically wiggle anywhere you place your hands, but it isolates the ball joints best if you do it at 3 and 9.

not sure of the parts numbers, but if you search theres a bunch of info on wheel bearing brands & parts numbers, as well as several writeups on how to actually go at it.