The Stovebolt Site Forums The Shop Area General Truck Talk When was Napco 4x4 first available on a half ton?

I am wondering when Napco first made a 4x4 system for half-ton GM trucks. Anybody know?

Basically, I'm wondering if it was for the 1955 first series or second series.

I believe first applications were for the war effort in 1941 or 42?

KMAC

1955 1rst. The '55 1rst and early 55 2nd Napco 1/2 ton systems are different from the later versions in that they actually used a 3/4 ton front differential with the 3rd member on the left side. It had a 3.90 gear, and the rear used 6 to 8 lug adapters to keep the wheels the same.
As far as WW2 Chevrolet 4x4s, the smallest I know of are all 1 1/2 ton. Dodge did make a 1/2 ton 4x4 in '41 for the military, as did IH, and I have heard of a few 1/2 ton Ford/Marmon-Herington conversions that saw military use. Might have to do a little searching to see if GM did the same.

WW2 Chevys and GMC CCKW used a GM corporate axle and housing, it was not NAPCO in any way. NAPCO tries to steal the limelight in claiming it was the first Chevy/GMC 4x4. Sorry, but not true as the military $$$ had them beat by at least 15 years. Look up Chevy "Banjo" axle.

Real early 1940-41 GMC and Studebaker trucks used a Timken front drive axle similar to the ultra rare pre war 1930's Chevy, and Dodge (perhaps Federal?) prewar military 4x4 trucks.

I am not a NAPCO expert and don't claim to be, but I am a rabid 4x4 enthusiast. I think the closed driveshaft was the limiting factor for NAPCO 4x4 systems so 1/2 ton trucks were never converted until Chevy/GMC went open driveshaft on their product line.

Dodge always had their own 4x4 configurations, after 1940-41; before that they also used a Timken front driveline (VC'S).

From 1942 to 1956 all chevy NAPCO's were aftermarket installs . In 1957 you could RPO right from the dealer order your chevy truck with NAPCO installed. Earlier versions used Dana 24's and 3/4 ton axles like Paul said. In 57 dana 23 was used and the axles were changed to passenger side . Half tons still used Dana 24's . But the 3/4 and 1 tons used the new dana 23 set up.
Earlier AD trucks were converted using the dana 23 system. (unsure of this fact) These conversions were not available for the 1/2 tons.

The history on NAPCO conversions for early 1942-to late AD body styles are sketchy for Chevy and GMC. While the company was certainly in business back then, the period photos and/or living examples are illusive.

the first NAPCO's were produced in the early 50's... I have heard differring opinions on when the very first ones were produced but in general say 1951 or later... all of these early ones were either 3/4 ton or 1 ton models as the 1/2 tons during those years had a closed driveshaft which hindered installing a tcase. In 1955 chevy went to open driveshafts which allowed the 1/2 ton units to be converted to 4x4

the first 1/2 ton models were late 54/early 55... these are really rare as they are specific to AD design models and only made approx 1/2 year. In 2nd half of 1955 they changed body styles... you could still get a 1/2 ton 4x4 but these were different than the 55.1 conversions as the spring perch dimensions changed and they are not interchangeable. The 55.2 TF 1/2 ton napco's are also rare as they only made these for a half year also before switching to a new design in 1956. The 1/2 ton systems are different from the 3/4 and 1 ton systems of the same period

All of the early napco conversions had a drivers side differential and used the rockwell 2 lever tcase (not spicer 24)

In 1956 the whole napco lineup was changed to drivers side pumpkin and spicer 23 tcase... these were continued until 1959... in 1960 GM made their own corporate 4x4 system and dropped the napco system.

Good info, thanks guys.


Except the 1.5 ton model? 1.5 ton NAPCO

Are these weird split axles Timken? 1940 GMC

I believe in 60-68, GM still used the Rockwell T221 Xfer case, same as Napco. Then the good old NP205 in 1969.

The axle on the 50's model GMC looks suspiciously like a military banjo axle.

http://g503.com/forums/viewtopic.php?f=25&t=225923

Do you know the provenance of that thruck...is it really a NAPCO, or did someone make a civy/GI hybrid?

Yes the "weird split axles" are the Timkens. I don't know all of the history on the Timken company, but those front drive axles appeared on various brands of trucks in the 30's.

http://vehiclesofvictory.com/gmc-g508/specifications/

Sure you're not thinking of the Coleman 4x4 conversions? All the information I've seen on Napco trucks point to the Spicer 23/24 T-case as the one most used. However, the Colman did use a 2 lever T-case of their own manufacture (model 22 part time and model 42 full time, all gear drive) that does resemble the Rockwell.
Napco 4x4 is the best place I've seen to find information about Napco trucks of all kinds.

Ive had lots of napco over the years and have never seen( or heard of) a spicer 24 being used on napco systems. Every napco ive owned prior to 1956 had drivers side front diff and rockwell tcase

both the spicer 23 and the rockwell have "mirror image" versions that change the drop to front axel on the other side. For example spicer 23's have passenger side drop... while 24's have drivers side drop ( I believe Ford used spicer 24's).

Rockwells on early napcos had drivers side drop while in the transition period (early 56) they used a passenger side front diff but used the mirror image version of the rockwell to provide a drop on that side (cant remember model numbers at present)

Not familiar with what equipment was used on Coleman conversions so could be similar... any pics?

Having a hard time getting a good clear pic of the transfer cases used. Axle pics are easy enough to find, but nor the 'cases. Here's one that I did find http://media-cache-ec0.pinimg.com/originals/6e/c6/af/6ec6af1caf1cfc2d572b23ddf6bd9ed6.jpg. It's in a '52 Chevrolet, claiming to be a "3800", but everything about it screams 4100.

Here's a Coleman ad showing a cutaway of the front hub and model 42 transfer case.

I am interested in the early napco's and particularly in the early AD versions... There seem to be mostly pics on the internet of early 3/4 and 1 ton versions.. But very few of the 1/2 ton models.. .. Anyone got any pics of these rare beasts?