2001 Tacoma, not engaging fwd gears

[Pitch]

I am over from the 80 forum, looking for some knowledge about my daughter's 2001 Tacoma (3.4, auto, DBL cab, rear locker, 4x4, 169K).

Backing up from initial start up is fine, but it does not readily engage the fwrd gears. It actually creeps fwrd slowly, but no change in rolling speed with increased engine rpm. I can run the shifter through Drive, 2nd, low, neutral, and no change in the end result. It will eventually catch with an audible, palpable, bang. Then fwrd progress is normal for a while.

No change when vehicle is hot vs cold. No change when it is garaged vs out in the cold (low teens *F)

Tranny fluid is older, but at the appropriate level.

No check engine or transmission lights on the dash.

If I jack up the rear end, both tires off the ground, and the TC and transmission are both in neutral, I can spin either rear tire fwrd or reverse x2-3 revolutions before the drive line binds up.

I am thinking this is a transmission issue; perhaps a valve body is stuck? Besides looking for disconnected plugs, what should the next diagnostic step be? Is a transmission flush worthwhile? Maybe freeing up debris in the mysterious inner workings?

Other thought (less likely) is transfer case. Again, 2wd-4hi-N-4lo: shifting is no issue.

Input appreciated!

 

[Mudder]

Is it supercharged?

 

[Pitch]

Is it supercharged?

Negative. Normally aspirated.

It has a small lift as well (1-1.5"), but I doubt that matters for the issue at hand.

 

[Pitch]

To follow up. Trans and TC were fine. The rear brake drum mechanism was getting bound up, compounded by oil contamination from a leaking axle seal and a bound up e-brake cable/mechanism. The wheels would turn fine in reverse, but bind up when moving forward after several revolutions. New axle seal, new brake shoes, and a freed up brake cable took care of the problem. Way cheaper than a trans-fix too.