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Well, I did end up pulling the speedometer out of the 300 cluster. I'm glad I did. It gave me a chance to lube all the gears and mechanisms inside.

But "While I'm in there" there is another issue I'd like to address; that of dim instrument cluster illumination.
I have replaced all the bulbs with the correct type, cleaned the dimmer rheostat, and still the lights are dim. Now that I have access inside I have a few questions about whether or not what I have is normal.

Inside the cluster the back-side of the chassis is bare metal, and the front is painted black. The strange part is the back is dirty/rusty and the front looks brand spanking new. This leads me to wonder if the front of the cluster chassis was painted black by a previous owner and is not reflecting enough light into the gauge glass.

Also, the bulbs have metal "reflectors" (for lack of a proper term) that surround the bulbs, boxing them in and only allowing light out the top.

From a Google search on this topic, a guy said that Studebakers had black-light filters over the bulbs and he thought Packards might have them also. Which kind-of makes sense as the gear shift indicator is this sort of arrangement on my 300.

So the question is. What's supposed to be in there and how's it all supposed to work?

Thanks Again!

Are you sure the dash light dimmer of the headlight switch is just not set to low?

Also the back of the cluster can get rust on it because of condensation that can drip down the inside of the windshield, and down the back of the dash board.

I don't recall anything over the bulbs 51 on. There may be a baffle attached on the inside of the cluster but it does not touch the bulbs. Is there a chance someone has added something or changed the sockets--maybe trying to duplicate the black light which I think was only 48-50. If the bulbs are in or out too far, that may also be a problem.

Yeah, I've bypassed the dimmer and they're just as bright.
I think I'm going to line the inside of the cluster with that reflective tape HVAC guys use. I think it's mylar. Should make it more mirror-like, hence more light.

I went to the hardware store and bought a black-light bulb.
I've confirmed that's not the issue.

I really think it's the black paint on the inside-front of the cluster that is absorbing all the light before it gets to the glass.

And I still have no idea what the metal boxes around the bulbs purpose is. Perhaps to make the light more even? Or so the bulbs don't glare in the instrument lenses? Perhaps they were once reflective inside. Today they are just metal shades that block all the light.

I have attached a photo of the "Baffle"
Top-down rear view from where I removed the Speedometer.

Attach file:

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I have my instrument cluster out and would be happy to take pics of anything you might need to compare. I do not have mine disassembled, but peering into the bulb sockets, they are not reflective inside. Just regular steel. I believe the baffles are to spread the light more evenly and prevent warning lights from being illuminated by the background lighting. You can kind of see the effect if you dim the lights and put a flashlight in each bulb socket.

Are you still 6v? I thought I read on here somewhere where a bulb chart was listed showing 6v bulbs that could be replaced with higher output versions (still in 6v) and go right in the socket. Is there resistance in the wiring?

Also make sure you grounds are good on the cluster. It really grounds through the mounting screws to the dash.

Very true, as my Vo-tech auto shop teacher always said, you can never have a good enough ground.

Whenever I redo a 51-54 cluster I repaint them gloss white inside with a spray bomb, and even blow a little white down behind those baffles.

Maybe someone already metnioned it, but did you check that the bulbs are #55s? Could be someone stuck a bunch of 12 volts in there. Generally I have not found illumination of those clusters to be a problem. Now, even road testers at the time complained that the hands did not show up well, but I've had very good success with flat white model paint on those. On long drives a night I usually have to dim the dash lights in my 51.

That's what I've decided to do, and am doing right now.
Everything is getting cleaned and the inside is getting painted bright white.

I have the whole cluster apart for a good cleaning.
One thing that's always bothered me is that the gels over the oil and batt indicators had fallen down when the tape got hot and goey. Instead of being half-covered they'll be all red again.
To me, those little things are worth the effort. I have to look at them every time I start the engine.

As Bigkev and Turbopackman suggested; I do think a lot of it was a bad ground going to the cluster. Once I Had the front bezel off the cluster I put on an alligator clip to pickup ground. The bulbs shone much brighter!
When I reassemble it I'm going to make a pigtail to get a good ground to the cluster.

I'll keep you updated... Speaking of which, I'd better get back in the garage and get back to work! Thanks Guys.