Go back to that dealership with a Zippo. Randomly flick it on and off as you negotiate, but don't pay too much attention to the fact you're holding it.
I'm being serious here; not the funny pyro stuff. When I was at a dealership looking at Mustangs back in April, a guy went in the office and did that. He was a big, intimidating guy too. He walked out happy as a clam because he got an extended warranty for no extra charge.
Something about flicking a Zippo is intimidating. Hmmm...
But really, that's a load of monkey crap.
IF you flip out long enough, you'll get the tranny done. If they downright refuse on such a stupid premise, then raise Hell. Call local TV news stations, papers, etc. Go back and ask again with a reporter behind you, but make sure to summarize the preceding events. If all of this really did happen on the last day of the warranty, the tranny is as good as free.
Otherwise, you'll have less of a chance. Dell pulled the same crap on me, but I was 15 and very naive at the time. I don't put up with that crap anymore. I bought a laptop and got a 1 year warranty on it. The HD and RAM died on the 363rd day and I called them on the 364th. "Allo? Yays. Nowah. Me sowway, yoo have to boy ah new hard darive and rammmmmmmm. Warranty expiyah. Wood you like place ordah?"
Bastards. Having worked in retail, I can safely say that the louder you are and more aggressive, the more you can squeeze out. I know that's a bad moral to play with, so ONLY use it when you KNOW you're right or being downright screwed. I mean, people used to buy brand new construction equipment, use it, bring it back the next day and want a refund because it was "defective." PHhht. I'd plug it in and it would work fine and they'd be dumbfounded. I said, "Oh, the defect must be that your work was done and you unplugged it, am I right?" Still, company policy was "100% satisfaction."
So, use that to your advantage. Being diplomatic can only go so far; it works when you're dealing with equally diplomatic people. When ignorance is abound, you have to fight fire with slightly-hotter-burning-fire. They're stupid; you're prepared.
I think the news reporters would be a good tactic. The dealerships don't want the bad publicity, so they're likely to compromise.
Wow, all this caffeine made me write a freakin' report. Enjoy.