The T-176 came later in the J Series run of production somewhere around '82. They were an aluminum-cased, light-duty tranny, and IMO they really did not belong in the big Jeeps. Luckily, AMC only put them in the J10s, because they really would have been silly in a 3/4 ton J20!
The struggling AMC most likely switched to this tranny in an effort to continue to offer the J Series at a competitive price.
I personally would not pass on an otherwise sweet truck solely because of the T-176, but you need to realize that it is not going to take the abuse that the older boxes will.
If you are planning to haul a little wood, home store duties, or bad weather type 4x4, the T-176 will serve you adequately
HOWEVER, if you are planning on bouncing 35" tires over rocks, or cube-van-pulling-clutch-smoking rescues, best be saving for a T18A!