Heavy vibration after rear diff fluid change

Hi,

I'm posting for my uncle who has an 06 Tacoma TRD Off road that he bought new. He's decided to keep the car even longer since it's been treating him well and asked me to change all the fluids. The car has 216k miles and has only had oil changed and the cabin filter after the fan failed. I believe spark plugs are original! since it's Denso on one side and NGK on the other. Engine Air filter was essentially clogged. Despite all of this, the car never misfired.

Anyways, after I changed the rear diff, the rear end has been vibrating bad, especially around 30-50mph. Here's what I did in order:

1)Valvoline 75w90 Synthetic
Vibration started, read about synthetic was a no no. He drove about 400 miles in that one week.

2)Valvoline 80w90 conventional
Vibration still there

3)CRC Limited Slip 7oz
No change

4) GM Limited Slip Oil 4oz
No Change

5) Coastal (Autozone House brand?) 85w140 conventional
Less vibration but still there

I did not see any LSD sticker on the rear diff nor the door jamb. There's a sticker for C9. It has an electronic diff lock.

Was I wrong to change the rear diff at 216k miles for the first time? It came out dark and thick with a goo on the magnetic drain plug.

What are the solutions to get rid of the vibrations?

 

And I've done 10 figure eights each time

 

rear diff original fluid at 216k miles.... yeah, id bet all the bearings in that diff are done... moms 07 4 runner just had the pinion bearings n diff carrier bearings after the fluid was changed at 107k miles... the bearings were toast.

The factory elocker diff could care less what fluid goes in, so long as its 75w90/140 no lsd additives are needed.

 

I forgot to mention that it only vibrates when you apply gas but once you let off the gas pedal it's smooth.

 

Just a thought.

check your U joints as it could just be that it happpened when it did and would have started even if you did nothing to the rear end oil..

 

Dif change is every 30k I believe.

 

I think I will agree with Mr Gadget for 10,000 dollars Alex!

Check the u joints in the drive shaft, at that mileage they are probably toast. On to of that it sounds like he wasn't too keen on maintenance... They have probably never seen grease.