I have had trucks with the so called TRU-STOP brake. If the rear seal of the transmission leaked just a little oil on them, they were worthless. If someone tried stopping a loaded truck with them, they caught fire because one brake is trying to do the work of four. If you lock up the drive wheels on slick pavement, you will switch ends before you know what happened.
I have parts and maintenance manuals for GMC 100 through 970 series from the late 30's until the early 60's. Its probably a total of about 20 books. One thing that I have learned about trucks with running them to make a living for 50 years is that if something wasn't produced for very long, it was a good indication that it wasn't very good.
