Just got a 91 B2600 with automatic. They said the tranny was out but it was extremely low on fluid. Which fluid is recommended for these? Also, are there any common problems to look for and are the parts available for a rebuild for these? A local shop said he wasn't sure he could get parts for it.

Thanks for all the great advice

 

Been using the Valvoline in my 97 k2500 4L80E for the last 50,000-60,000 miles. I think it's great, shifts great and in the extreme cold you'd Nox Vidmate VLC hardly know it was cold.