I have moved washer drain over to garge sink. Have tried everything from snaking to Liquid plumber. Whne i removed the small acess plate it shows that the washer drain is connected right at the bend of the tub. House built in 77 bought year ago.
Did you move the washer to the garage sink because it was draining slowly in its normal drain?
Does the garage sink drain to a different place?
Is there a "cleanout" access outside the house that will let you reach this drainpipe?
Is the tub on a slab or is there a crawl space under the floor?
The clogged drain is still the most likely option. A renter had a tub clog, and I snaked and plunged and Dranoed and nothing worked. Finally I gave up and called a plumber, who looked down there with a little camera and then snaked it out. It took him about 15 minutes. Turned out to be a piece of soap or something. I think it cost me $125.