93 Grand Marquis transmission problems?

[Balthamos]

This problem just started 2 days ago. It's the 4.6 ltr overhead cam. I was driving it and when it excels to 3rd gear, it acts as if the brakes are applied. It will not shift further than 3rd. At about 23 mph, there is a slight shake in the car, and it slows down to about 10 mph. I've never had this problem before. Any of you knowledgeable people out there have some input on this query? I will reveal more information if needed.

[fredjacksonsan]

More info needed...Reveal! Reveal!!

A little more description of the problem would be helpful....during these speed changes, are you keeping the amount of gas the same, or adding or reducing throttle? Did this problem happen all at once or gradually? Have you checked the fluid level in the transmission? How many miles are on the car?

[Balthamos]

Throttle is being increased. It just happened a few days ago. Came from a fill-up at the gas station. Was speeding up after a stop sign when all of a sudden WHAM. Felt like your getting whiplash in an airplane :P. Yeah fluid lvl in trans. is up to par. It's got 123k miles. When it gets to a certain speed (I think 23 mph) it'll act as if the brakes are applied and just bog down till 10 mph then let go as if nothing happened. *shrug*.

[fredjacksonsan]

Very strange...It sounds like your transmission needs some help. You may want to have a diagnostic computer hooked up to it, especially if it does this all the time.

[6502dude]

When did you change transmission fluid & filter last? If it has been more than 40K than it should be done as part of maintenance plan.

When pan is off, have a look for debris in bottom of pan. If none - this is a good sign.

Many transission shops will provide free assessment, even without doing the fluid & filter change.

GMs did have a problem with shift to neutral under heavy trottle problem caused by shift solenoids and updated solenoid design twice before 1996 model year. However, most of the time this problem ocurred when at highway speeds, not from a stop.

I would try the easy route first with transmission fluid & filter change as this often cure a lot of transmission quirks.