I have a 95 T100 4x4 ext that is close to rolling over to 200K miles. So far things have been pretty good (I bought it at about 170K) My biggest complaint is that the 3.4 seems a bit weak, if I find the slightest hill at 65-75 mph it unlocks the converter and works itself to death to keep up.

I also have some bad rust at the top of my windshield on both sides, anyone else?

Even when I have the cruise on any long hills I pop off the OD button and then no problem... leave OD on, and I watch my trans temp creep higher as the engine and trans search for the best way up the hill.

Mine does the same, especially in cruise. Sometimes if you ease down real slowly on the pedal on hills it will delay the downshift some, but other than that, yes it does downshift real easy.

Mine as well. And just one bag of animal feed seems to be enough weight to start making it pop on level ground. Ok, maybe not, but it's pretty durn close.

I think it's a common thing with the T100. The 3.4 works much better in the smaller, lighter Taco than the T. I just bought my 3rd T from Wisconsin a few months ago, and drove it straight to TX. Even with the small 235/75r/15 tires at the time, it would down shift often.

Several years ago on my first T100 where I was running 35" tires and stock gearing, the problem was even more pronounce. It got to the point that the temp light would light up often if I was to travel out of town for longer freeway speed.

On my current T, my plan is to just keep tires @ 33", and add a much larger transmission cooler for the truck. By turning the OD button off would also help control the heat, but sacrifice a little on MPG.

I just had my transmission rebuilt due to running it out of fluid after the trans cooler line ruptured. The first thing I noticed was how much better it held in overdrive on hills. Now it hardly ever unlocks the converter unless there is a steep hill. My gas mileage went up too. Noticable increase of 2-3mpg. I would guess that as the transmission/torque converter wear that it tends to unlock more often.

Step 1, make sure the engine is set up, timing, etc. Then make sure your gearing is close to factory, oversized tires will kill it, if you dont change your differentials, specially if your engine is over 100k miles. You should get some relief. Stock size tires dont' look as cool... but...
footnote, this is not a T100 think, it happens to any vehicle as it gets tired...

Might want to talk to IPT (import performance transmission) about your prob, the re-do valvebodies and torque converters and it will be alot cheaper to fix it now rather than after is blows up....