i have a k 3500 with 4x4 when the trans is dead cold or warms to operating temperature the trans will not shift up at 35 mph my scanner is showing me a code 87 which states a high ratio and i have no clue and either does a local trans shop his info on the cd's. i am stuck and lost please help
thanks
pete

More info, trans type, year of truck, and engine size, also any mods to the truck would be helpful.