There's a nylon bushing where most GM seats pivot that's worth taking a look
at. Get to a parts breakdown from GM and check it out.

Joe--ASE Certified Parts Specialist & 10th Ann.Club Tech Director
'80 Carousel Red Turbo T/A, 27k orig.
'79 "Y89" 400/4 speed 10th Ann. T/A, 57k orig
'84 Olds 88 Royale Bgm 2 dr, 307 "Rocket" (lol), 143k and still going....

I might be totally off base because I've never looked at the seat guts on an
84 Bird or Blazer.  However, I had an 86 Cadillac (I know, the seats don't
look the same, but the guts may be similar).  There was an L-bracket on the
hinge in those seats.  It was a shitty, low-quality bracket and it had a
tendency to bend backwards.  BUT, it would only bend to a certain point and
then it would stop.  I ordered a  new bracket from Cadillac, put it in, and
that one bent within a few months.  Finally, I asked my cousin (who worked
as a welder at a place that made semi-trailers) to make me one out of heavy
gauge steel with a little arm brace.  He did, I installed it, and never had
the problem again.  So, I could be COMPLETELY wrong about this when it comes
to the Bird and Blazer, but I thought I'd throw it out as an idea just in
case.

FH674