The short version:
I bought a car, the keys were lost
decided to replace my 89 coulumn to save money
bought a 91 coulumn
I read that they don't interchange

Can I just replace tumbler?
can I make it work?
please help

 

You will have to know what #key you are supposed to have first. The keys have resistor pellets in them. There are 15 different keys with a different resistance value fo each one. Do a search and find the key resistance chart, I'm sure it's on this site somewhere. Get a new lock cylinder from gmpartsdirect.com or the dealer or the like - the vats lock cylinder comes with a dumby key that's got the correct cut on it but no pellet, it will turn the cylinder but will not start the car. Then try each resistor value one at a time spliced into the wires from the lock cylinder until you hit the one that works (wait 5 minutes between each try). Then tell the dealer what number key it is and they will get a blank with the appropriate pellet in it, use the dumby key to cut the blank. This is the method to restore vats to working order.

If you don't care about vats and have no key then I'd just get a standard lock cylinder and key and find someone to help you remove the vats programming from the mem-cal in your ECM. (Or if you figure out the resistance just leave that resistor spliced into the wiring to the vats module.

 

thanks for the reply, I think I've got a game plan now.