VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 37-38 taillight lense variations question

Ive had my 37 coupe since 1969, also had a 38 coupe, a 37 sedan and aquired another 37 coupe this year. So Ive ammassed quite a collection of spare parts.

Specifically on the taillight lenses...
Dont get me started on blue dots... hate them!

I have several glass lenses with diamond pattern inside and the circles in the center. I assume these are all original or GM replacements.

I have several plastic lenses that are actually pretty authentic, I assume these are 59 cent Western Auto etc from the 1950s.

I have one pair that are glass, diamond pattern inside and no circles, no numbers, no letters.

Where did these come from?
Canada?
In glass I assume they are GM?

The "square" lens was first used in 1937-1938 for passenger cars. The it became the lens for trucks from 1940-1953. Was used on some misc. applications in between. Went through a major change in mid 1948.
Prior to 1948 the genuine Chevrolet lens was glass, had circles in the center and the name "Stimsonite"(spelling?) in the glass.
The mid 1948 lens changed to a form of plastic (Lucite) and The GM Guide name (and part number) was on it. Reason for change as per Chevrolet "The new lens has better optical properties , throwing a better beams to the back of the car"....in other words the light was brighter, they no longer had to pay for the use of the Stimsonite name and made their own Guide Division of GM lens.
They are much brighter with the plastic lens and it also reflects light better.
A glass lens with no circles is aftermarket. Due to the wide used of the lens there were many after market version sold - and not all exactly the same.

I know the diamonds are supposed to make it work as a reflector in case the bulb is burnt out.

I am surprised any one back then made a "copy" in glass.

Im going to run the glass ones without the circles and confuse people...LOL

You will find the the glass with no circles will give the poorest light transfer. On a sunny day the driver behid you will not be able to tell when tour brake lights are on. Those lights need all the help they can get. With the original specified 15 candle power brake light bulb they are almost impossible to see in day light. If you stuff a 21 CP 1129 bulb in the socket they are just a litle better......my choice for safety would be the plastic lens and a 21 CP bulb and with the interior of the tail light painted white.

White paint is good.. also see that Chevs of the 40s has a "reflector" to add inside the housing at $9.50 each.

Its a bit surprising GM would make a change on a part in mid 48 that would not carry over to 49.

Maybe there were complaints?

Or were they actually selling a lot of replacement lenses at the parts counters?

The 1949 cars had a completely different lens and they were plastic as were all lenses from that point on.
The trucks used the same lens up thru 1953 and a running change was made in mid 1948 and again from there on all were plastic (Lucite). The plastic lens for the 1948 car had a different look to them. Was difficult for the average person to tell if the square the car/truck lens in question was glass or plastic.

ok got it.

Keep forgetting pass or truck...

these are 37/38 pass and trucks and SDs 40-53?

(As a side note I saw one on a Harley last weekend that had a repro truck assembley as its brake light and it looked at home)

Makes sense there would be running changes and many aftermarket efforts.

I went to the garage.. the red glass plain no circle lens held up to a 100 watt light bulb looks almost yellow not red... so I see what you mean they are a poor choise.

However comparing the GM glass and the GM plastics the glass ones seem much better... with the plastic the diamonds just arent reflecting any light...

Funny that they made the backup lenses for 57s out of glass... not plastic..

They would have been smart to make the 1957 tail light lenses out of glass.....then they wouldn't break when the gas spilled on them.