Piston Slap: Not Exactly a Rugged Mountaineer Edition

TTAC Commentator NN writes:

My wife’s 04 Mercury Mountaineer (V6, AWD) recently hit 65k miles. The transmission had been clunking around noticeably lately, and I realized that:

a) These trannies are prone to fail

b) We hadn’t yet changed the ATF on the vehicle.

I am aware of the argument that some people make that when tranny fluid is old not to change it because the varnish build up, etc. helps to hold things together. But I thought 65k was still pretty young so I told my wife to take it in and get the fluid changed. She took it to a local non-franchise, non-dealer mechanic–just a fluid change and flush, no filter change as the mechanic said it wasn’t needed. The very next day the “O/D Off” light starts flashing constantly, which suggests that the transmission needs service. This is the first time we have seen this light.

My first thought is to make sure the mechanic did everything right on their end…i.e. didn’t leave the fluid level too low, etc. But in the end, I think this transmission is shot…as noted prior, it clunks in and out of reverse (with a delay usually), runs the RPM’s up during shifts like a slipping manual would, and clunks hard into neutral when coasting to a stop, also. My guess is that we are a textbook case of the last bits of the tranny holding out with the old fluid, and the flush was the end of it. The car, otherwise, is well liked…and paid off.

My question for you is what to do if the tranmission is indeed in need of service. I have read on other forums about how some fixes (solenoids, etc.) can run up to $1,000 and only solve the problem for a few months. Should I just pony up the $2k for a rebuild and hope that will last for another 5 years, or should we consider dumping the car? These Mountaineers/Explorers have a history of this transmission failing so I don’t want to play around and want to get to the bottom of solving the problem quick…this is my wife’s car, after all.

Sajeev Replies:

NN, if nothing changed since you emailed me, your nightmare scenario is not very likely. Most importantly, make no judgments until you find the error code that created the warning light! This is just as true for transmissions, especially with electronic 4WD systems with far more electronic stuff than yesteryear’s trucks and SUVs.

The only fly in the ointment is access to a transmission code scanner: sometimes you need to get a more sophisticated computer scanner than what’s normally offered. Luckily, with a $100-ish deposit, you can rent the correct scanner from many parts stores. So do just that, or get the codes from the mechanic.

Again the codes are crucial: don’t listen to the mechanics diagnosis, ask him for the code and the diagnostic tree followed to come to their conclusion. Like the Grand Marquis recently discussed (http://www.thetruthaboutcars.com/piston-slap-friction-modification-for-the-mighty-mighty-marquis/) a bottle of LubeGuard Red might be the only thing needed. I’d throw a bottle in right now, and see if anything changes.

(Send your queries to mehta@ttac.com)