With my z32, I had to pull the antenna motor to replace the mast.  I have done a few antennae in these cars.  When they go bad on their own, usually that means the plastic cord inside the antenna mast is broken, which necessitates a pull of the antenna motor to retrieve the broken part of the cord inside the motor spool.  This time I bent my antenna mast by backing out of my garage before the door was all the way up.  Therefore, the plastic cord inside the metal mast was still good, and I could simply thread a new mast in place without having to remove the antenna motor from the car.  As long as the antenna motor can still be heard running when the radio is turned on and off, try replacing just the mast before pulling the antenna motor.   

I had used only OEM antenna masts from Nissan up to this point.  This time I tried a mast from www.AntennaMastsRus.com.  They list their masts as also being Nissan OEM.  I was intially pleased with the results.  The cost for a mast ordered through AntennaMastsRus including shipping was $24 (See bottom of page for follow up).

A second person is helpful to turn the radio on and off while the antenna is being worked on at the back of the car, but I did this job by myself.    

I am sure a special tool exists to remove this nut, but this method worked fine.  I used a hammer and fine point punch or awl.  Uh, don't slip and scratch your paint. 

I squirted some PB Blaster between the nut and the mast the night before and the twenty year old nut came off easily.  Tap gently at the right angle and spin the nut counterclockwise.  

Remove the nut and the black plastic sealing flange underneath.  Have the helper turn on the radio.  As the old mast begins or tries to come up, grab it and continue to pull the entire antenna is out.  Mine came out easily on the first pull.  If the mast seems to be stuck, then the retaining sleeve is probably corroded.  Spray some more PB Blaster down in the hole and wait overnight.  Their should be nothing holding the mast in at this point, so don't be afraid to pull.  If the antenna won't come out then the motor has to be removed from inside the hatch, then disassembled.

Note the direction the teeth are facing on the white plastic cord as the old antenna comes out.  On my car, the teeth were facing FORWARD, toward the front of the car.  When the new mast is threaded in, the teeth must be oriented in the same direction.  This is fairly obvious as the teeth will be on the inside curl of the old cord.  

Be sure to slide the retaining sleeve off of the old antenna mast and transfer it to the new one.   There is not a new retaining sleeve provided with the new antenna.  

The metal sleeve above keeps the new antenna mast from shooting out of the car after  it is installed, and grounds the mast to the stereo receiver. 

Old mast with retaining sleeve removed.  Notice the teeth on the inside curve  of the white plastic cord. 

The metal end of the retaining sleeve goes over the small end of the new mast, and then slides all the way to the bottom.

WIth both of the antennas out of the car, set the metal masts at equal lengths, and make sure the white plastic cords are also exactly the same length.  If the plastic cord is shorter on the old antenna, look at the end and see if it looks like it was broken off.  If there are any broken pieces of cord left in the antenna motor, then the antenna motor will need to be removed and taken apart so the broken piece of cord can be removed. 

If the old cord is shorter and there are not any broken pieces in the motor, then the motor is probably aftermarket and not OEM.  In this case, the new mast will not work.  The white plastic cords inside the old and new metal masts must be the same lengths. 

Thread the new mast in the hole and have the helper turn on the radio.  Wiggle the cord keeping the teeth facing forward until it catches.  The cord does not have to catch immediatly so keep trying through the entire cycle the antenna motor is running in the on position.   Thread the metal mast into the hole once the threads catch.  I have never seen anyone get this right the first time.  Multiple attempts are the norm.  If the cord does not thread, back the cord out of the hole, turn the radio off, wait for antenna motor to power down, then try again. 

Once the cord catches and the metal mast is in, replace the black plastic flange and tighten the retaining nut by hand.  Do not worry if the antenna is not fully retracted yet.  The antenna will fix itself after turning the radio on and off several times.  After six cylces of  turning the radio all the way on and off, my mast was extending and retracting like it should.  Tighten the retaining nut with a few gentle taps of the awl.  Finally, with the mast extended, spray a paper towel with silicone and wipe down the mast. 

New mast installed after six on/off cycles to get it to completely retract.

July 2011 - The "AntennaMastsRus" antenna did not last long.  Got stuck in the up position about three months after installation.  When I pulled it out the antenna and plastic cord seemed fine, but I replaced it with an OEM antenna from Nissan, part # 28215-F6506.