Differential Issues

I’ve got a 96 Tacoma 3.4 manual with 4.10 gears. Started to get the notorious whine from my rear end. Found a used 3rd member on Craigslist. Was supposed to be 4.10 gears as well. Swapped it, noise went away and all was good. Drove it ~1000 miles. Driving down the highway and rear end locked up on me. Was able to trailer it using 4wd but not without alot of grinding. Drained the oil, no immediate big chunks of metal. Jacked the truck up and turned the axles to no weird noises. Filled it back up and gives alot of noise from rear end, mechanic wants to tear it apart. Anything else I should do besides drop the third and look inside?

 

If you want to look at it you can use a endoscope most likely only beneficial if your plan is to get another rear end from a junk yard or something. It’s probably not making noise because it does not have the weight of the truck on it(could possibly use the parking brake for resistance). But to fix it you’re probably going to have to take it apart anyway. What oil did you use?
Good luck.

 

Mechanic put it up in the Air and said it was howling pretty good. I used a Valvoline 75-90. Going to pull the third and take a look. Probably will pull the axles as well and have the shop press on new bearings