What are common problems with the transmission in a 1990 Cadillac Brougham?
The 1990 Cadillac Brougham uses the THM 700R4 (4L60) automatic transmission, which has several well-documented issues that owners should be aware of:
Most Common Transmission Problems:
Torque Converter Lock-up Issues - The converter may fail to lock up at highway speeds, causing poor fuel economy and overheating. This is often due to faulty wiring or a bad lock-up solenoid.
2-3 Shift Problems - Many owners report harsh or delayed shifting between 2nd and 3rd gear. This is typically caused by worn governor gears or valve body issues.
Throttle Valve Cable Misadjustment - This cable controls shift timing and firmness. If improperly adjusted, it can cause early or late shifts, or even transmission damage.
Overheating - These transmissions run hot and can fail prematurely if the cooling system isn’t working properly or if the vehicle is used for towing.
Sun Shell Breakage - In higher mileage units (over 100k miles), the sun shell can crack, causing complete loss of reverse and 2nd gear.
Prevention Tips:
The good news is that when properly maintained, these transmissions can be quite reliable. If you’re considering this particular 1990 Brougham in Huntsville, I’d recommend having a transmission specialist inspect it before purchase, especially given the unknown mileage.
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