Rear differential problems

My 1999 4wd 4runner which I have owned for 16 years,and is still a pleasure to drive,has now 252.000 miles, I have a whining noise coming from,I believe to be my rear differential,but for me difficult to pinpoint the cause,could it be the bearings in the rear differential,or perhaps the gears in the pumpkin?Anyone has a thought on this?Thanks so much.
I am new to this forum,and excited to be here.

 

Tires?

 

Just looking at the best case scenario. Are they worn? Maybe rotate?

 

I looked at the best case scenario,unfortunately it is not the tires,Cooper evolution with about 15.000 miles,after doing some more research,I have come to the conclusion,it is most likely worn bearings in rear differential,the pitch of the noise changes when I press,let go and depress the gas .I am hoping not having to replace the entire pumpkin?

 

Na simple rebuild. Not much to it, If you know what your doing....@Fourtoad would definitely know your answer.....

 

Are you sure it is not the brakes or wheel bearings?

 

Pinion Pre Load.
Same issues with my 2000 trd sr5 with 4.10 ratio.
Accelerate and release gas then hear how long or grinding gears. Apparently what happens is there is a set of bearings pressed inside with the pinion gear. That pinion gear has to be tightened just right because it's still needing to be free spinning inside the bearing and also seal to prevent fluid loss. When you accelerate, the pinion and its bearing is seated tighter however when you release the pedal then the pinion is allowed to "slop" back out there's when the noise is heard. So we've put another rear differential in my truck yesterday. This morning it died. Completely shredded itself inside. Now I must tear it back apart again to find out why the newer replacement failed. My old part is sitting on my front porch now. Many people have claimed you could snug it just a little with an impact to loosen the play. Too much will ruin it completely. Too little and it will still whine. I'm going to reinstall my original and see what happens but, to answer your question yes it is bearings just not wheel bearings but pinion bearings.. you can also upgrade to non crush sleeves as well but only if you follow the specs. All bolts and everything must be done just right. Installing a new sleeve is easier said than done. Without tools. Torquing bearing preload on the pinion gear requires a special torque wrenches that measures in inch pounds and not in foot pounds and then you have to free spin the pinion with the torque wrench and get the resistance to be about 6-10 inlbs for my specific 10 bolt differential. So no things aren't always as easy as just do it yourself. Some things are complicated and messy and require time that all of us do not have. Not to mention finances... However I hope I can install my original part and the whining is somewhat fixed temporarily until I just end up getting a nice quality part matched to my truck someone else spent hours preparing and rebuilding with a guarantee and then go ahead and do the repairs because nobody likes making the same repair multiple times repeatedly.


Still wondering what caused this replacement to just fail so suddenly too. I had plenty of gear oil and it drove fine for about 35 miles then crushed itself inside...