I've had my 2004 Express 3500 for about a year and my problem has to do with the headlights shaking or vibrating as I go down the road. I did replace them both (entire units) a while back but am unsure if the problem was there with the old ones. It is really only noticeable when I am behind another vehicle. Has anyone else had this issue? Any ideas? I did check the mountings and all appears as it should.

 

Composite or sealed beam?

 

Composite

 

I would remove them (very easy), remove the two bolts on top, paying attention that the bottom feet are in the slotted area of the frame. Then make sure the bulb sockets are completely latched in. If everything is good so far, remove the sockets with the bulbs, see if there is any looseness with the bulbs. Can't think of anything else that would cause the shaking.

https://chevroletforum.com/forum/att...1&d=1504030847

 

There is a gasket that comes with the new bulbs. If you replace a bulb, then sometimes the old gasket comes off the bulb and sticks to the housing. When you install the new bulb you are doubling up on the gasket and the bulb wont lock in properly.
If that is not the issue, then I would do as stated above. Make sure the housing is seated properly before adding the bolts.

 

The bulbs are HIDs and the housings were new so I reckon the gasket issue you described would not apply. But I should probably check for any looseness. I did ensure the housings were properly seated.

 

You failed to tell us you installed HID's, pretty sure that's where your problem is.

https://chevroletforum.com/forum/att...1&d=1504181309

HID Flickering Problem ? Reason and Solution :: Modify Street

 

I have them too. On mine the lower mounting feet are broken and allows the entire unit to shake. The street signs look like strobe lights and I'm sure in annoying for the folks in front of me. I would double check the mounts on the housing.

 

Have you figured out the cause yet ?
So many times I read threads that are
Incomplete....

 

Most of the time we never hear about the outcome of the problems people have with their vehicles.