2002 DoubleCab Transmission Problems - Time for 4x4 Swap??

I picked up my DoubleCab back in September of 2013, and it has given a few years of fairly trouble free service, despite the 204K on the clock. Sometime in 2015, I started noticing some oddities with the transmission. First, it the RPMS would fluctuate while cruising at 65-70. Not by much but noticeable. Next I got a CEL for code 770 - Shift Solenoid E. After doing some reading on here and a few other places, it seemed to me that the causes and solutions to this CEL were inconclusive. Factoring in the price of the solenoid - $200-$400 from what I read, and I decided I would ride it out. I did change the transmission fluid, which looked decent nonetheless. I then noticed that the transmission developed a significant whirring sound when warming up and clunked when going into drive if I did not let it sit and warm up for a while. All this is going south in my mind. It finally came to the end of the road this past weekend. It started making the noises in the video below. That is taken while idling back and forth in my driveway holding the iPhone down below the door.



So - unless someone thinks that noise is NOT the transmission, I think I am due for a new one. Looking at picking up a used one and swapping it in. Because the truck is a Prerunner, this brings me to a convenient juncture - should I go ahead with a 4x4 swap?

Maybe I just put a 2wd transmission in and then try to horsetrade/pony up for a 4wd model?? Haha - and no I don't have the money to do a SAS at this point. I wish...

I know there are several threads on this matter and 5-speed swaps and all. Heck - I have one myself - swapped a 5-speed into my 1998 4runner when the milkshake got me...

I was looking to get some feedback from y'all on my different options though. I was thinking of either (1) just putting in a 2wd again and looking out for a gear driven case and pairing that with Inchworm's Prerunner adapter, (2) getting a 4wd transmission and pairing it with a gear driven case with Inchworm's case adapter, or (3) getting a 4wd transmission and sticking with a regular old Tacoma transfer case, j-shift model, maybe going dual case in the future.

I am not in a huge hurry as I still have my 4runner to get around in, but I don't want to leave this thing sitting for months on end. I figure 1 and 3 get me back on the road quickest. 1 would probably be the quickest and cheapest - not factoring in the adapter and geared case - just thinking back to the road. But, I think 2 might be the best in the long run.

Any thoughts? Truthfully - not that familiar with the Inchworm products. There may be a better product out there, too, not sure. Anyway, let me know if you have any suggestions.