I have an '88 Brougham D'elegance with the 307. A few months ago, I noticed that the transmission started to slip. This only seems to happen after at least a 10-mile highway drive. Then, the transmission balks and has trouble upshifting 3rd and 4th gear. If I floor the pedal, it will overcome it and downshift with a jerk. When I stop at a light, I can feel the car downshift to 1st okay like normal and then the car starts up fine until it gets to 3rd gear.

Once the car cools down, it doesn't do it again until another highway drive. If I stay off the highway, it doesn't happen no matter how much city driving I do.

I had the transmission fluid drained and the system flushed and added a bottle of Lucas transmission fluid to the system which is supposed to stop hard shifting. The technician who changed the fluid said that there were no metal shaving in the pan and that that was a good sign of no serious damage. However, about a week later, after a highway run, the problem came back.

Do I need a transmission overhaul, or is there some other problem here that might be hopefully less expensive?

I would change the fluid/filter once again, and ensure that the filter is not loose. Since there was no shavings, I am really at a loss what else could it be, other than the transmission is overheating (heat=lower viscosity=slippage), in which then you'd need to flush your radiator 'n such.

Just a ponderance, I'm sure there are better tranny guys here.

Has anyone adjusted the TV (throttle valve) cable. It's simple to do and might make a difference.

Also, like Spock said, you might have an overheating problem with the engine which would cause the tranny to run hot.

How many miles?

120k from a 200R-4 in the big body is average..... get to the 140-160k and you may as well be getting it rebuilt soon.

Been there done that!!!! Four words pal....

Torque Converter Clutch Solenoid

$150 fix....

Thanks guys for the input.

Dopestar, I like your car. It's identical to mine. :bouncy:

Can you help me out and elaborate a little bit more on what you were experiencing with your tranny and what I need to tell my mechanic? I can't seem to find a good technician in this city who will actually take the time to diagnose my car properly without jumping to the conclusion that something need to be replaced or completely rebuilt.

Thanks guys for the input.

Dopestar, I like your car. It's identical to mine. :bouncy:

Can you help me out and elaborate a little bit more on what you were experiencing with your tranny and what I need to tell my mechanic? I can't seem to find a good technician in this city who will actually take the time to diagnose my car properly without jumping to the conclusion that something need to be replaced or completely rebuilt.
http://www.cadillacforums.com/forums/rwd-19xx-1985-deville-fleetwood-1985/67912-transmission-problems-diagnosed.html?highlight=Transmission+Problems

I had a hard downshift to 1st at red lights. Upshifting and downshifting 2nd to 3rd was rough and there was what felt like a slip. Now I have a perfectly fine shifting transmission. Before the TCC Solenoid was replaced I had a tranny flush and my transmission mounts were broken so I had them replaced too. Good luck, I've got a feeling this is your problem.