Would a dirty transmission filter on 1990 Cadillac sedan deville cause it not to shift out of low gear?

A severely clogged transmission filter in a 1990 Cadillac Sedan DeVille could absolutely contribute to it not shifting out of low gear. The filter is crucial for keeping the transmission fluid clean. If it's clogged, the fluid can't flow properly, leading to insufficient hydraulic pressure to actuate the shifting mechanisms. This lack of pressure would prevent the transmission from engaging higher gears.

However, it's not the *only* possible cause. Other problems that could cause the same symptom include:

* Low transmission fluid: Related to a clogged filter, but can also be caused by leaks.

* Faulty transmission solenoid(s): These are electrically controlled valves that regulate fluid flow for shifting.

* Worn clutch packs or bands: Internal components wearing out can prevent proper engagement.

* Problems with the valve body: This controls the fluid flow within the transmission.

* Transmission control module (TCM) issues: Electronic problems can prevent proper shifting commands.

While a dirty filter is a strong suspect, a proper diagnosis requires a mechanic to check fluid level, pressure, and potentially perform further testing to determine the root cause. Just replacing the filter without investigating other possibilities might not solve the problem.