Will Sea Foam transmission and engine products be safe to use in older vehicles with automatic transmissions and carburetors? [SOLVED]

Thanks for the question!

Yes, Sea Foam products are compatible with older, carbureted vehicles like your GMC. Both Trans Tune and Motor Treatment don’t contain harsh chemicals and are made with petroleum ingredients that can’t harm engine parts or components.

I’d recommend using Sea Foam High Mileage in the gas tank of your GMC. It’s a strong cleaner. For a cleaning dosage, wait until you have a low tank of fuel (1/8 tank or so), add 2 cans of High Mileage, and drive at least 20 miles (until almost empty) before you refuel. The high concentration works very well to clean fuel residues and deposits.

In your transmission, just follow the directions on the Trans Tune can.

Let me know if you have any other questions – happy to help!