The T-100 was based on the 1994/1995 4runners and initially had the 3.0L engine. after they got the 3.4L, they weren't all that much better. The Tundra has the same front differential as a 1996+ 4runner. it has a 8.4" rear, the same as the NON-TRD tacomas that has been widened for the increased...
I had a similar first gear problem. I ran GL4 from the dealer for a little bit but it grind ed too much and I could literally notice when it was breaking down from the heat.