most likely transmission, if TC goes you tend to lose all gears. Whining is usually a good indicator your going to be doing a rebuild.
So basically a new trany is my best bet then.
a replacement tranny with some sort of warranty or rebuild the one you have, but let a shop make the final diagnosis, no sense in jumping to a conclusion
Looking for a Used Suburban in your area?
CarGurus has 24,095 nationwide Suburban listings starting at $1,799.
Search Chevrolet Suburban Questions
Chevrolet Suburban Experts
Related Models For Sale
Used Cars For Sale