I spent a summer afew years ago working in a transmission shop. This is complete BS, fed by old, stupid mechanics, and transmission shops that would rather rebuild/swap your transmission.
Start by flushing the fluid.
Afterwards, adjust the throttlevalve cable to provide a shift like you want it. The tighter the cable, the earlier, and harder it will shift. The looser, the later it will shift & the longer it takes (clunks into gear b/c of insuffecient fluid pressure running in the valve body).
I think that's a bad idea. TT-IV is
NOT a replacement for Dexron specified transmissions. While Toyota is generally behind the curve in lubricants, they are very good at rating lubricants. They specifically state in the TT-IV tech primer that TT-IV should not be used on Dexron transmissions, and original TT-I transmissions. They would stand to make alot of money in dealerships if it was.
Dexron isn't compatible with any TT fluid.
Personally, I believe them.
As a side note, alot of people go with different transmission fluids on other makes to try to improve the shifting qualities, as all ATF's have different friction properties. If you wanna give it a whirl. Whatever floats your boat!
The bst I can tell you, is that if you experiance *any* slipping in the transmission. Park the car, flush the fluid & go again. Driving a slipping trnasmission for just a very few miles will destroy the clutch packs in very short order & leave you with no option than a rebuild/replacement.
Back to your problem. I strongly suggest going to walmart and buying afew jugs of Super-Tech Dexron III. It's cheap (Around $5 for 4 quats), a basic mobil 1 ATF (So you know it doesn't royally suck), and it's good to flush with because of that.
If you're not comfortable flushing the transmission. Drop the pan & clean everything. Put it back on & refill. Idle the engine & shift into all positions on the gear stick. Drive the car around a few min. Park & shift back into every position.
Stop the engine, let it sit until you're not afraid of burns, drain the pan & refill.
You should do at a bare minimum of 2 pan & refills on that transmission circtuit to statistically change the majority of the fluid. On a personal note, you should do 3 drain & fills. & a great idea for someone that NEVER flushes a transmission is to do a drain & fill with every oil change until you can get around with it.
(Just like adding an auxillary cooler & possibly filter, will solve more than 90% of transmission failures.)