Thanks all..This continually occurs whether warned up or not. A little history..Van sat in field since 1985, has gone to varnish, replaced gas lines, restore going pretty good until... Replaced coolant lines, put about gallon slowly adding over time with the help of leak via couldn't line exit orifice, No burnt fluid . Checked levels going through gears, , going to check linkage. And go from there possibly adjust band s), but I don't think that's the problem... Thanks
Put shifter in "2", check for engine braking when you close the throttle. If no engine braking it's a rear clutch problem. That's the last part to come out when you take the transmission apart. Have fun.