It absolutely is a GM tranny...a French built 5l40e....
If my memory is right...8 qts. It's in the DIY above.
As a side note....
I had a gmc pickup with the predecessor tranny...the venerable 4l60e and got a little over 300k miles with fluid changes every 25k. It's an auto so YMMV but the General knows what's its doing after all....they've been building automatic for an extremely long time....Heck hot roders still love using the turbo 350 . And that tranny brings back fond memories of getting scratch at fwy speeds by hitting the accelerator hard in my dads 68 firebird conv.
Last edited by x3brian; 01-08-2013 at 10:30 AM.