Rear differential? Dog tracking, etc.

'Evening everyone.

Truck: Tacoma doublecab, 4x4, 90k miles. No "real" off-roading, but some pulling occasionally.

Background:
In May, sideswiped curb hard (with front, I thought); got wobbly steering.Few days later guy stops me in parking lot ..."Dude, your truck is going down the road sideways." (I look at it, but not obvious; but in hindsight ... dog tracking.) Into dealer for alignment. Seems better. But ... I notice that when I am driving in rain, I get this strange sensation of hydro-planning. I am suspecting my crappy new tires (that I got in Feb). THEN (early Aug): Another guy, at a highway exit, jumps out of his truck and says ... yes ... "Dude, your truck is going down the road sideways !" So, I bring it to another place, and YES, spring center pin is sheared off (he gives it back to me; it's rusty ... hmmm). But, here's where I come to the matter ... the new place says "we replaced the pin, and put on new u-bolts (they were bent?), but it's still not fixed because ..." (here it comes) ..."there is something wrong or bent in the rear differential." $2500 (new, could go used for less) to replace. (I believe it's an "e-lock differential.")

So, 1) does that seem reasonable at all? the differential? not a bent axle perhaps? or 2) is this total BS, and it just needs more adjustment? (I still seem to feel the wobble in the steering.) Thoughts?

 

I would think the frame is "diamond" before a bent axle.

Are you experiencing odd vibrations? A bent axle will cause that.

A true frame shop can diagnose the issue better than any other shop.

 

Vibrations in the steering, yes. (Alignment still off?) But general vibrations, no.
On the bent/mis-shapen/diamond frame, could I diagnose that myself (measure from point A to B to C, etc.)? That seems possible ... (Frame shop, as you said, would be better.) Thanks for direction to investigate.