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Old 08-30-2022, 10:37 PM #1
patrickdotryan patrickdotryan is offline
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Join Date: Jun 2019
Location: San Diego
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patrickdotryan patrickdotryan is offline
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Join Date: Jun 2019
Location: San Diego
Posts: 7
patrickdotryan is on a distinguished road
Power Antenna internal fix + photos

Hi all,

I know there are other threads on antennas, but if you've replaced your mast with an OEM one (not the thinner eBay ones) and still get grinding noise, hopefully this will help:

Assumes you have the new mast, either installed or not. It's less springy to pull apart if the mast is removed first!

Removing the fender liner:
IMHO you should remove the back half of the liner so you get good access to the antenna motor. This way you can let the motor hang to do your repairs, rather than disconnecting your antenna from the radio and pulling the signal cable out from under the dash, since it's behind ducts etc.

Remove the vehicle wheel with the car on one jackstand.

Remove the 10mm hex screws. All around the inboard edge of the liner, go into the engine bay and squeeze the back of the fender liner clips and withdraw the clips. You can leave the front ones (near the headlight) attached so the fender liner still hangs from the front of the car. For Base and SR5 models, do the same around the outboard part of the wheel arch.

Limited models have a plastic fender flare covering the outboard plastic clips that the screws go into. These prevent removal of the liner. You don't need to remove the fender flare. These clips are dirt cheap, so save a bunch of time - with a blade inserted behind the fender flare screw tabs, cut the heads off the plastic clips and push the clips through into the hole. There is one hidden about 10" above the running board. Have a friend pull the fender flare out and cut the head off that one too. When reassembling, use new clips there. Part number is 90189-06212 "Fender Liner Grommet". Pull the liner towards the engine bay and then downward. Let it hang.

Access the antenna motor
You'll now see the antenna motor. From inside the engine bay, squeeze the plastic clip that holds the power harness connector to the inner fender / body. Once that floats free, you can access and squeeze both tabs to separate the antenna harness from the vehicle harness. Remove the 10mm hex screw that attaches the base of the motor to the vehicle. On top exterior of the fender, place a rag around the antenna if you like your paint. Remove the crown nut from the antenna by tapping the slot with a screwdriver. Unscrew and support the antenna motor as it will now hang down. Set up a low stool so you can work on it!



Remove the black tape and carefully lift up the motor's raincoat. From the front of the motor, remove the 4 screws from the face, one screw bottom right (mounts to bracket and holds earth strap) and the center bolt, being careful to catch the nut from the back - it's easy to lose.



Remove the front cover. You will see this, but with more yellow grease. The outer ring is a loose retainer for when the mast's flexible rack is curled up inside. This is shown with the mast removed.



Set aside the retainer and you'll see a central toothed hub. If you still have your mast's flexible rack installed, it will come down the left side and tuck under the lip of that central hub.



If no mast / rack is installed, pull that hub forward / up off its axle. It is split around its circumference, but it will lift off its axle as one piece. If your mast / rack is still installed, it will feel like that the hub doesn't want to come off the axle. But if you pull with your fingernails, you will actually separate the front of the hub from the back part and now without the front lip interfering, you can push the rack aside enough to withdraw the mast as if the antenna is being raised, then remove the back half of the hub.

Inspect the teeth on the two halves of the hub. If they're all destroyed and worn totally flat, you're possibly out of luck and may need to find a junk truck to find a better one of those. My experience was that mine were a little flat, and that was part of the reason that they didn't properly engage with the small pinion that you see poking out in this next image. That is the part I fixed and I suspect it is a very common problem. Read on.



If you previously split the hub, now put it back together and set it aside. The front face of the hub has a male part that fits between two spring tabs in the back half. Be careful not to misalign it 180deg so that male part goes in the other non-springy female recess. You will know you mated it correctly if the two parts fit back together snugly, but that if you twist them opposite to each other, you will see the teeth briefly misalign under spring tension, and then bounce back into alignment. This springiness is what tells the motor to stop winding the mast up or down.

Lift the white nylon housing from the motor's worm gear.




The pinion that engages the hub will remain. You can see it appears to have been designed with some play between itself and its axle. However, as its teeth and those of the hub become a little flat over the years, they no longer always engage. This is where the grinding noise comes in. It's horrible.



Find yourself some sort of small, preferably nylon rod or cylinder that is smaller in diameter than the inside of the pinion. It does not want to be tight. Hardware stores have spacers and studs that would work. Mine had a very small central hole, so I had to drill it out until the center was large enough to slide over the pinion's axle. That part can be tight, but doesn't need to be. As long as there is some free rotation that a little grease can fit into.



When you have it sized just right, slip it over the axle.



Then put the pinion back on. There should hopefully be just a little play now. Pack it with grease. For plastic parts I always use SylGlide silicon braking lubricant.



Put more grease onto the back area of the housing, then drop the hub onto its axle.

With the cover still off, the hub installed, but NO MAST INSTALLED yet, temporarily plug the unit back into the vehicle harness. With a greasy gloved finger, hold the hub lightly in the center (so it doesn't fall off the axle). Get a friend (or an enemy) to turn on the radio. The hub should now turn, as if trying to extend the antenna. It will run for a bit, then time out. Have your lovely assistant turn the radio off. The hub should rotate the other way, then time out.

If all that works, good job. You could button it all up now, but suspicious as I am, I do one more test. BEST DONE WITH GLOVES ON. Still holding the hub in place, have the friend turn the radio back on. The hub will turn and time out. Once stopped, carefully feed the mast's white nylon rack into the tube at the top of the motor until it just engages. Teeth need to be facing inward so they will engage with the hub's teeth.

No need to put the loose retainer back at this point. Make sure you're ready to feed the rack into the antenna motor, then tell your friend to turn OFF the radio. The motor will start to turn, and pull the rack and then the mast into the motor. Keep feeding it in until the whole thing is retracted. The rack will spool loosely out all over the place. Don't worry about that yet. If you weren't fast enough to push the whole thing in and it stopped short, have your friend turn ON the radio and take the mast out fully. Then try again with the whole radio OFF / feeding-as-fast-as-you-can thing.

If you're REALLY thorough, you can screw the crown nut back to the top of the antenna (important, otherwise the mast won't stop and will just spit out on the floor!). POINT THE ANTENNA TO AN OPEN SPACE - NOT INSIDE THE FENDER OR YOU WILL BEND IT! With your finger on the hub (and trying to avoid the moving toothed rack), ask your friend to turn the radio. The antenna should now extend and after encountering the resistance of the crown nut, it will stop.

If all of that tests out, retract the antenna again (radio OFF) and lightly coil it into the loose retainer ring, pack it with grease, put all the screws and ground strap back together, slide the rain coat back down and tape it back up with electrical tape.

Installation of the rest of it is the reverse of the disassembly. Notes: Mount the antenna motor to the bottom bracket first, since the crown nut compresses the rubber collar on top of the fender and may pull the assembly too far up. For Limited models, feed the fender liner back between the fender and the fender flare. Carefully pry back the fender flare's tabs so you can insert your newly purchased clips / grommets into the square holes to retain the liner. After those are all installed, screw the 10mm screws into the clips.

Rock on.
__________________
My daughterís 1998 4Runner Limited
160,000 miles
California truck, clean, no rust, no salt roads.
2WD

Last edited by patrickdotryan; 08-30-2022 at 11:07 PM. Reason: Did photos the wrong way!
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