2010 4Runner 4WD slip yoke

You never named the issue.

It's difficult to describe the exact problem. When releasing the brake from a stopped position, there is a very slight "jump". Occasionally, I will feel it when cruising, and I just take my foot off the accelerator (but not braking), causing the vehicle to naturally downshift. My son, who is a Lexus mechanic, drove it and felt the problem. He said it's possible that the driveshaft slip yoke (or sleeve yoke) needs greased, because it may not be sliding freely along the driveshaft. He greased it. But, as I said, it did not last.

I think your son needs to take a closer look at it.