According to Chiltons, Manual Transmissions all models 1976-1986 f-100 through f-350 and bronco 1978-1986 use SAE 85w/90 gear oil.
1985 F150 XLT Lariat 5.8L (351w) HO 4bl 4X2 ext cab. 8 foot bed.
"Some people spend a lifetime wondering if they've made a difference, Marines don't have that problem." President Ronald Regan 1985
D.A.V. USAF 1976-1992.