[James Lamb]

I'm sure the Blazer and Suburban parts are different because I'm pretty sure a few years ago when I had to replace my rear window motor nothing interchanged. But, on the Burbs you had to be careful to realign the regulator gears so they were matched - that is, so the left side of the glass was not rising faster than the right, etc. And you could get things lined up such that the window glass would go all the way up but not all the way down, and the reverse. There were stamped marks on the regulator to line things up. Any chance you have a similar issue? For that to be the case it would mean someone before you did something to the rear window and did not get it lined back up correctly.

And good luck. I fought mine for a long time, ended up having to fabricate some new parts that are no longer available