Piston Slap: Friction Modification for The Mighty-Mighty Marquis?

Jeremy writes:

Hello Sajeev, I have a 1993 Mercury Grand Marquis that I picked up from a family member a couple years back. I registered the car in my name with only 37,000 miles on the clock, it now has just over 51,000. The car was garage kept for years. I have updated the fuel filter, spark plugs, tires, air filter, and the regular oil changes.

After driving the car for a while I noticed the transmission shifted with a slow “shudder” from 3rd to 4th gears. The transmission seemed to shift smoothly under light acceleration but mild to brisk acceleration is accompanied by the transmission shudder.

I checked around online and found that this is not an isolated case. In fact, Ford released a TSB on the issue with this transmission. The TSB stated the transmission fluid needed to changed to handle the problem. I took the car in to an Ammaco last month for the fluid and filter swap. I picked up the car for a test drive and the transmission shifted without the shudder. Within a couple of hours the shudder was back.

I am completely lost on this issue. I do not know if the transmission shop dropped the ball on the fluid swap or if the transmission might be shot. You help is greatly appreciated!

Sajeev Replies:

And here I thought the mighty-mighty Marquis was completely bulletproof! Every website has the Ford Panther Chassis faithful blogging to that effect. Of course, Ford’s less-than-stellar tranny track record since the dawn of automatic overdrive transmissions is common knowledge, even to the fanbois.

Luckily this problem has a quick fix, especially at your mileage: damage to the transmission’s hard points aren’t likely. Yes, you needed the switch to Mercon V ATF (Mercon III was from the factory) but sometimes that isn’t enough to fix the shudder. Because there’s no miracle cure in a bottle.

Well, except when there is. Ford had a similar transmission problem with Explorers circa 2004 (rough engagement into drive). They couldn’t use the Mercon V excuse again, after 10-ish years of using it at the factory, so they recommended a friction modifier: in this case, a bottle of Lubeguard Red. People on various Fat-Ford forums agree, and I my mother’s (former) Lincoln Aviator absolutely loved to shift after the dealer added it. Or so I remember.

(Send your queries to mehta@ttac.com)