My 99 Grand Marquis went into passing gear and stayed for a while but went back to normal is this an omen transmission problems to come?

Asked by Jul 05, 2015 at 01:03 AM about the 1999 Mercury Grand Marquis 4 Dr LS Sedan

Question type: Maintenance & Repair

I'm a little worried. I have a 99 Mercury Grand Marquis LS, 168000 miles. I was driving
on the highway and noticed my temp was flickering and noticed it was in a higher gear
possibly passing and motor was revving high didn't hear immediately because windows
were open.I pulled over listening for gear changes came to a stop thinking gear
indicator on steering column was indicating wrong took off again and felt and listened
for gear changes in acceleration all was normal, all smooth gear changes no jerking
and it was fine the rest of the way home checked fluid at home it was normal and only
8000 miles on flush. It hasn't done it again since my question is this the beginning of a
possible major problem?

1 Answer

80,295

It could be. Having a high mileage transmission flushed is sometimes bad news. I would have recommended to change the transmission fluid and filter at 100,000 miles but not a flush. Parts wear over time and usage. That's normal. As wear occurs tolerances get larger and things don't work quite like they used to. The good news is the crud and junk floating around in the transmission fluid actually helps worn parts work better longer. By simply dropping the pan and changing the fluid and filter you're actually only replacing about 1/2 of the total fluid capacity. This "freshens up" the fluid and at the same time leaves enough "junk" in there for those worn parts to keep working. By flushing the fluid you make everything "squeaky clean" in there like when the transmission was new. The trouble is that the parts are worn now and without the "junk" in the fluid to grab onto the transmission won't work as well. You might try changing the filter again as it may be clogged now. But put the old fluid back in. Just top it off with new if you come up a little low. Whatever you do, don't put any additives in there. Doing that will only make things worse. The only transmission additive I recommend is TransX. I've seen it work firsthand if you follow the directions on the can to the letter. HTH. -Jim

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