I would suspect that they used the wrong fluid, but that is going to be very hard to prove now. Some places use a so-called Universal fluid that they claim meets or exceeds all manufacturer's specifications, but I'm very sceptical of that when ig comes to Mercon-V.
When I get my transmission flushed, I am charged a bit more because the Mercon-V is more expensive.
If you did not get any guarantee, they may just say that the problem existed before you brought in your truck for the Flush? I have always told the place that does my transmission flushes that they are welcomed to test drive the vehicle before they do the flush, so that any problems after the flush were caused by them and they will honor their guarantee. They have never test drove the truck, and fortunately I have never had any problems after a flush. In fact my vehicles have always drove and shifted better than they did before the flush. But I also know that they use a 100% Mercon-V compatible synthetic fluid made by Pennzoil. I even seen the lard drum it comes in, and watched the whole flush process to insure that they used the correct fluid, and that nothing improper was done.
...Rich
