90 Caddy trans code: overhaul or flush?


My 90 Eldorado, 86,000 miles, drives fine, but the service engine light is on and I am told there is a “hard code” indicating transmission problems. A trans shop said the solenoids are going bad and it needs to be overhauled. I asked if changing the fluid would help (it hasn’t been changed in a very long time and I live in hot Phoenix, AZ) and they refused to do it, saying it would make the problem worse. Can you tell me if changing the fluid might help? The value of the car makes the overhaul not worth it.


That sure sounds like an odd statement from the shop. I think you should try another place. The solenoid part sounds funny.


I got a 1993 Caprice with 44k miles in 2002. I took it to my regular mechanic to get the trans fluid and filter changed. He was reluctant to do this at first. His rationale was that a layer of “varnish” builds up on the inside surfaces of the transmission from the old transmission fluid. Fresh transmission fluid would cause this “varnish” to break loose and clog up the interior passages of the transmission. Although the transmission fluid was 9 years old, it appeared to be in good condition (red, not burned or dirty). I decided to have the fluid and filter changed on the condition I would not blame the mechanic if there were problems afterward. I’ve had no problems since then.

In your case, I would get a second opinion from another shop. I would get a fluid and filter change instead of a flush though.

Ed B.


It would be nice to know exactly what the code was.

In general Changing fluid (as opposed to a flush) is not going to hurt a transmission. In some cases it can help it, in all cases it is likely to extend its life.

The problem is that most people wait until there is a problem before they have it changed. Then they change it and the transmission fails. They tend to blame the failure on the fluid change. In reality the problem was more likely the result of not changing it sooner.

The real pro on transmissions around here is Transsman. If he responds, he will have the best answer. Give him a few days, he is not here every day.