Headlight gear fix (highly pictorialized)
 

After the recent fun I had upgrading Mrs. Patches' A4 drivetrain, I was coincidentally in the garage one evening when Mrs. Patches pulled in and proceeded to lower her extended headlight modules. During said process of lowering the headlights, the driver's motor gear assembly was heard to emit a horrendous rat-a-tat-a-tat of a machine-gun cacophony that announced the arrival of the headlight gear malfunction known all too well to these forums. This was a rather disparaging occurrence considering the tender age (mileage) of this particular C5 which was still a bit south of the 5-digit mark.

All disconcertions put aside, I set about ordering a couple of repair kits, one for the existing ailing driver's gear and one for the when-it-rains-it-pours failure of the passenger-side headlight I predict is shortly to follow. I decided to only change the broken driver's side so as not to totally shoot the weekend to Hades and because I just wasn't in the mood.

I ordered and received the latest kits from Top Down Solutions which is essentially the same kit sold by another vendor and contains the same reinforcement T-bracket and started the repair (with a couple of modifications to the included instructions).

The kit contents. Top left-clockwise: Silicone lubricant, T-bracket with rubber bushing and plastic washer, brass gear, rubber gear insert, adhesive mixing stick and Urethane two-part, quick-cure adhesive.
Attachment 48169510

I raised the hood and layed out protective mats and towels. Here's the headlight I'm about to tear into. Then I raised the headlights by turning the stalk all the way and then backing it off one click to turn the headlights off but leave them up. I then disconnected the negative terminal on the battery.
Attachment 48169511

A closeup of the gearmotor assembly.
Attachment 48169512

I unscrewed the three Phillips screws from the plastic shroud . . . Attachment 48169513

. . . and the four Torx screws from the painted headlight cover and removed them.
Attachment 48169514

A rear view of the gearmotor and one of the mounting bolts.
Attachment 48169515

First, I disconnected the main headlight connector . . .
Attachment 48169516

. . . and then the two connectors behind the high and low-beam bulbs.
Attachment 48169517

Front view of the gearmotor. Here you see the three mounting bolts. There are nuts on each bolt that need to be removed. There is also a nut on the other end of the center shaft you see that goes through the offending gear we're looking to replace. I used a gear wrench and a box-end wrench to unbolt these and was very careful not to drop the nuts as it's a tight fit for my hands in there. Removing the center nut allowed me to slip the linkage arm off the gear shaft and that immediately caused the headlight to freefall/pivot so I was careful in easing it down as I removed the gearmotor.
Attachment 48169518

The instructions indicated that the headlight assembly should be loosened and slid forward to allow removal of the gearmotor but I found I could remove it without doing that. Here's the extracted component.
Attachment 48169519

And here is the free-hanging headlight assembly.
Attachment 48169520

The next step is to use two small screwdrivers to pop the gear cover off. The cover appears to be ultrasonically welded or glued.
Attachment 48169521

I was careful and slowly worked my way around the cover until it popped off in one piece.
Attachment 48169522

The exposed gear shows no obvious sign of damage - yet.
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I removed the gear and shaft.
Attachment 48169524

Here's the exposed gear case. Note that the worm is metal.
Attachment 48169525

Finally we can see signs of damage to the gear on the teeth at the bottom of the picture. Doesn't seem like much, but there's not a whole lot of engagement to begin with.
Attachment 48169526

The damaged teeth are at the top in this pic.
Attachment 48169527

I cleaned up the gear case, installed the rubber insert into the brass gear, lubed up the gear, shaft and worm with the silicone grease, slid the gear and plastic washer onto the shaft and then the gear and shaft into the case. Then I prepared for the adhesive application.
Attachment 48169528

The instructions warn you to work fast when gluing the cover back on because there is only about a 5-6 minute working time once the two-part urethane is mixed. They aren't kidding either. It's important that both surfaces have adhesive applied to them and that it is a contiguous ring all the way around the edge of the case to ensure the case is watertight.
Attachment 48169529

I clamped the cover snugly to maintain pressure while the adhesive cured overnight. I used the remaining adhesive to form a bead around the outside of the case/cover interface.
Attachment 48169530

The next morning, I removed the clamps and checked for a good bond. Then I slid the T-bracket onto the shaft with the larger end of the rubber bushing towards to cover to retain it. The T-bracket was added to the kit after reports of cover separation due to adhesive failures caused by axial load of the gear shaft. The bracket helps to keep the cover in place. I also slipped a metal washer between each bracket arm and the cover to take up the space in between - this was one of my additions to the procedure.
Attachment 48169531

Next, I reinstalled the gearmotor and reassembled the headlight in the reverse order of disassembly, making sure to slide the linkage onto the gear shaft in the proper orientation. Incidentally, the headlight position was out of synch with the passenger side because I installed the gear shaft in a different position than where it was before I removed it (it was about halfway up). Not a problem because I simply manually rotated the motor worm using the knob on the end of the motor until the headlight was in the fully raised position. Finally, I reconnected the battery, tested the headlight raising/lowering action and confirmed it was working properly.
Attachment 48169532

All fixed with only a modicum of fuss. :thumbs:

Great write-up. Thanks Patches :thumbs: :thumbs:

Chuck

Thanks for the excellent writeup Patches. I'm going to be tackling this in the near future and these pics and instructions will be invaluable.

:iagree: Awesome write up and something I have done on my drivers side:cheers:

Much appreciated writeup with all the detailed pics. Even I should be able to do that fix now when it happens to me, which it inevitably will. :thumbs:

Funny, it must happen in waves. I replaced my driver side headlight gear just two days ago. :willy:

Got mine from Rodney Dickman and you're right, they're exactly the same kit. Took about an hour to take it out, 45 minutes to repair, and about an hour to put it all back and test. Not all that bad as repairs go.

Glad to see yours went as well as mine. Photos are great, I just have trouble stopping m work, taking photos, and starting again. That trip to the fridge always distracts me somehow and I forget what I was working on,,,,,:rofl:

Patches,
another amazing thread. :thumbs: You have great attention to detail and amazing patience when posting these. When reading one of your "how to's" I feel like I can tackle any job. :thumbs:

I have posted a link to your shifter installation instructions countless times. I don't have a headlight gear problem but bookmarked this thread in case I do.

You are truly a great asset to the Corvette community.

Thank you :cheers:

Awesome writeup Patches. Going to keep this one on file for future reference.

Great write-up as always. I have my two sets of Rodney Dickman Gears just been waiting for a free weekend.

BTW - Did you notice any additional motor noise after switching to metal gears?

Once again thanks for helping educate us all :thumbs:

Once again Patches...OUTSTANDING!!:thumbs:

So far so good, but if my lights start acting up this "keeper" Tech Tip will be my guide for the repair. :cheers:

XLNT write up plus pictures!

Gets an A++++++ in my book! This is a keeper!

Thanks,Matt

Nice job Ed!! Thanks for taking the time and putting forth the effort!! :thumbs: :cheers:

Once again Patches shares his know how with us lesser mortals..LOL
I just know I will have to do this sooner or later and now I know how.
Thanks Ed

Great write up Patches. Thanks for taking the time to put it together. I'll drop that one into the archive.

Thats one job that figures in my future. I had one motor gear replaced under warranty and since fitted the heavier T85 headlights. I have 2 gear kits from Rodney waiting to go in. The write up will come in really useful.

:cheers:

As usual :thumbs:
Just bookmark this page but hope you also put this on your website ;)
Thanks so much!!!
:cheers:
-Mike

You are the MAN! Great post, it will help a great deal of people out.:thumbs:

The new gears are as quiet as the old. Nothing to hear except the little bump whne the light gets to its full open/closed position.

They should sticky your posts!

Nice write up!!

As usual, a great documentary :thumbs: