I just did some glass install recently with the help of an old pro. He used trans fluid in the past!,but not on mine. On mine we used string and soap. Also DO NOT use the newer style sealant, get the old Butyl? or tar-like sealer in a caulk tube, it never sets up hard-which is what you want-it needs to stay flexible over time. Very messy.
As Ted says leaks show up other places too-heater cores, wipers. On t-birds the water can come up thru the windshield frame and out into the interior, regardless of the top seal or windshield seal.
It's amazing to me the difference the new glass makes now in my car. I can see!
A L A N F R A K E S ~ Tulsa, OK