Piston Slap: Mercury's Final Mistake?

TTAC Commentator SupremeBrougham writes:

Hey Sajeev, I decided that I want to try my hand at throwing a Piston Slap topic your way: my grandparents gave me a 1995 Mercury Mystique LS that has been passed around our family since new. The car has 121k on it, but the motor (V6) has about 40k fewer miles and the trans (auto) now has around 15k total.

Here is my issue. When pulling out from a stop, the engine revs to almost 5000 rpm before shifting gears, regardless of how gentle I am with the gas. I want to have it looked at, but here is where it gets tricky for me. My grandfather, who worked for Ford in Transmission Engineering, and my uncle decided to take on the task of replacing the engine and trans in this car four years ago, as a final hurrah for my grandpa, as he is getting up in years. It took them six months, but they did it. The car went on to two more uncles before coming back to my grandparents, and then on to me. My grandpa gave me the car with the stipulation that I was not to put any more money into it. And if anything was to go wrong with it I am to bring it back for repairs. But I live almost 200 miles away, so that isn’t so easy.

What do you think might be causing the trans to wait to shift? Oh, and once under way, if I have the need to “floor it” to get it to change gears, it won’t do it. It feels like it turns into a CVT.

Finally, my grandpa also says that I shouldn’t drive the car with the OD engaged around town, as it will mess up the Overdrive band. I have no idea about that one. Perhaps you might???

Sajeev Answers:

Richard, any trouble codes present? You need some time with an OBD-II code scanner (free at many parts stores) before I can go any further. Of course, your 1995 Mercury Mistake (sorry, Mystique) probably has OBD-I, and very few places scan those for free. Luckily, the scan tools are either cheap (about $30) or free (a paper clip inserted in two specific pins on the test ports).

You take no action without scanning for codes, but the horror stories of transmission rebuilds failing shortly after their 12 month warranty expires are far from uncommon. And if you didn’t buy an upgraded reman transmission from a reputable brand (Ford, Jasper, etc) or installed a junkyard part of questionable heritage, I suspect you’ll fall prey to that of countless others: a mechanical problem inside the Mystique’s transaxle that is so labor intensive, so painful, that another rebuild is in order.

The end of the world? Hardly. Given your family’s history, your TTAC handle and passion for American Iron, the Germanic-Midwestern charm of a Mercury Mystique is easy to understand. The car looks pretty in the pictures, so time to do the right thing if the codes give you no clarity: get another transaxle. But this time, do your research on the company/person in charge of the rebuild to make sure it’s a good one. Take it from the guy who owned a hi-po Ford AOD that everyone thought was absolutely amazing, getting the right rebuild makes even a junk design look like a superstar.

Send your queries to mehta@ttac.com. Spare no details and ask for a speedy resolution if you’re in a hurry.