my 4x4 won't engage when i press the button for 4hi or 4lo. The light will blink and it sounds like the transfer case is engaging(almost a clanking sound), but it won't lock in. please respond with ideas or thoughts.
Please let me know if i should post this in a different area!
thanks in advance,

 

Tim,
It sounds as thought the front axle central locking actuator is bad.
Easy to replace.
GM also recommends that you replace the lube in the front differential with 75W90 Synthetic Gear lube on the older Tahoe's, this will enable the front propeller shaft to rotate easier and allow the vehicle to lock into 4-wheel drive quicker which will reduce the strain on the actuator and also synthetic lubricant reduces the operating temperature as is a better quality product.