Tranny problem on '94 Concorde, help!!

Here's to hoping enough people still read this forum...

I have a '94 Concorde 3.5L with 140K miles. Yesterday I drove 160 miles on the interstate only to have my tranny stick in low gear after waiting at a stoplight at the end of the exit ramp (I understand this is known as "limp mode"). Luckily I didn't have far to go, so I parked my car and left it. When I came back two hours later and drove the car, the problem seemed to have disappeared. I didn't notice that the shifting was any more sluggish or rough than usual (the usual being on the slightly slow side). I took a chance and drove it the 160 miles back home and it still seems to be fine. The fluid level is normal, too.

For a little history on the car, I had a tranny flush done last summer, and I dug out the receipt to find what fluid they used. It was ATF-3, which I have read is not the best, but I haven't noticed anything with the tranny before now. I also had the water pump clog up this summer, which melted/jumped the timing belt and mysteriously fried (of all things) my ATC unit (this was my second one, too!). I don't know if this would've had an effect on the tranny, though. Finally, it has been in the upper 90s with very high humidity for the last couple weeks -- could the heat have had something to do with it??

I'm going to take it to a couple different places this week, but I wanted to see if anyone might have some speculation/advice on the problem first. I'm not familiar with the area, either, so I don't know whether I should trust the dealer or try a tranny shop like AAMCO or a more local establishment.

Thanks in advance for any help!

Update:

I took it to a recommended transmission "specialist" and he did a diagnostic on it. He found one soft fault, the overdrive pressure circuit. Everything else checked out ok. He said it could be a one-time glitch, but that if something happens again in the next week or so, it's gonna need work and it might be a number of different things. He told me not to feel bad, though, since the average lifetime of these trannies is only 125K miles. That didn't make me feel much better.

Anybody else have experience with this?

I have a 1995 LHS and a 1995 Concorde as well, the manual on these cars suggest a fluid change every 30,000 miles. ATF + 4 is the correct fluid for Chrysler tranny(replaces ATF+3). If you have the extra money, I suggest a tranny flush, and I always use Lucas Tranny stop slip, Worked for me.