on the rear of my 84 300 sd there is a casing that i needed to replace the gasket on. Does anyone know what the torqe rating is for this particular gasket?

If you are talking about the rear cover, the BOLTS that secure the cover are torqued to 10-12 ftlbs. The large nut that holds the flange is torqued to 75-85 ftlbs.

sorry about the mistake
 

Im sorry, I guess i wasnt paying much attention to what I was writing. I was trying to get the torqe ratings for the casing on the rear of the transmision. Also the torqe rating for the large nut that holds the gears together.

Correct specs 8mm(bolt) = 13mm wrench size
 

Those specs are the ones that you asked; for 8MM bolts that are rated at 8.8 hardness, MAX torque is 15ftlbs. MB suggests that for this application 10-12ftlbs is correct. Many times when a gasket is involved the spec is lower than MAX. Also when torquing the rear nut, it should be NEW and have lube on the threads.