I just had my auto trans rebuilt by Houston Automatic Transmission Service on SH 249 at Grant Rd - don't go to the other shop on Shepherd.
The 249 location did a great job on my '91. I have over 1,000 since the rebuild. They go back with all new internals. They are a little higher cost, but they do the upgrades. They have a good reputation around my area.
Talk to Ben @ 281.890.4400. Alex is one of the best rebuilders around. He keeps a very neat and clean work area.
If it is transfer case, Call Texas Auto Gear and talk to David 713.697.0388
These Guys helped me out with a really difficult trouble shooting issue.
If you have any questions, let me know.