Chefman43223
Newbie
Thank you !Like they said, the HM290 is a light duty transmission, would have only come in 1500's and 2500 "light duty" (7200 lb gvwr) trucks. Your truck being a 3500 wouldn't get the light duty transmission. So, being a 1988, it gets the SM465 granny low 4 speed, because the NV4500 granny low overdrive 5 speed didn't hit the scene until 1992.
Richard