Before installing your new mast, compare the old mast with the new one. They need to be identical in every way.  If they are different, you may have an after market power unit.  Also it is very important that you NEVER cut the white cable on the new mast at any time.

     1. Remove the nut on the outer end of the power unit where the mast comes out of the car.

    2. As someone turns the radio on and as the mast begins or tries to come up,... grab hold of it and pull out the old mast...taking note which direction the teeth on the plastic cable are facing so you know which way the new mast cable is to face when you put it in.... Make sure that the short outer grounding/retaining sleeve ( as what is on the outer NEW antenna mast ) has come out with the old mast, this is very important, as this is what holds the antenna mast in when the nut is fastened..... If the old mast and grounding/retaining ring are out then proceed with step 4. If not proceed with step 3.

    3. If at this time you can’t pull the mast out and it seems to be stuck, more than likely the grounding/retaining sleeve is corroded to the top of the antenna tube. What one needs to do at this point is inject an aggressive penetrating oil (kriol oil works great or equivalent) between the outer mast section and the brass threaded tip of the power unit. Let it work overnight and then try to pull it out again. If this doesn’t work, then you need to take the complete power unit out of the car and put the tip of the power unit in a jar of aggressive penetrating fluid overnight. The next day reinstall the power unit back into the car and proceed with step 2. If at this time the old mast comes out proceed with step 4.

    4. Compare the old mast with the new one, the length of the white teethed cable MUST be the same length of the one you took out of your power unit (DO NOT CUT THE NEW MAST CABLE).... If the cable is not the same length, then you probably have a broken piece left in your power unit.... If the cable is shorter proceed with step 5.... If the over all length of the stainless portion of the mast and diameter are the same along with the white cable length continue with step 6.

    5. There are occasions where the antenna cable breaks off in the power unit and will not allow the replacement mast to be pulled in all the way. In this event you will have to remove the power antenna assembly from the car and disassemble the drum assembly and manually remove the broken portion! Once the cable is out, clean the grease off of the drum assembly before you reassemble the power unit. Once this is done, use a light grease or white grease on the drum assembly, then reinstall the power unit in the car and proceed with step 6.