The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1947 - 1959 Chevrolet & GMC Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 04-25-2012, 08:41 PM   #1
Bo Duke
Registered User
 
Bo Duke's Avatar
 
Join Date: Feb 2010
Location: Lincoln, NE
Posts: 31
1956 Napco GMC

I'm working on a truck for a guy I know. It titled as a 1956 GMC Napco 4x4. It's a 3/4 ton, with the rare Eaton HO front axle. He pulled it out of the junk yard, and there's a lot of mysteries on this thing. I'm trying to figure out what is original and what isn't. The truck is titled as a 1956 GMC, but he was told the original title was lost. I checked the ID tag inside he door, and at least the cab is a 1956 GMC

First- The VIN show's a factory V8. It does have an older V8 (has the script Chevrolet valve covers) but I haven't pulled the #'s from the block yet to see what it is for sure. I question it being a true factory V8 truck though, since it's a Napco (it seems like most conversions were straight 6's?) and the engine mounts are made of plate steel, welded to the frame. So either it's a old V8 swap, or the factory mounts failed at some point. Any other way to tell if this is the original cab and VIN plate?



Second- It has a Chevy hood and a GMC grill. The grill has has "100" on it, which I believe is 1/2 tons. So maybe someone swapped the front clip, and ended up with a Chevy hood?



Third- How can I tell if this is the original Transfer case? Are all these shims between the t-case and cross member factory? How about the 4wd shifter location in the cab? There's an un-used shifter hole up closer to the trans shifter. The T-Case has a name plate on it, but all I can really read is "Spicer" and 20x (last number isn't readable). I don't think this is a NP201 though.








And a couple random pics, since everyone loves pictures


Front axle

Lock out hubs
Bo Duke is offline   Reply With Quote
Old 04-25-2012, 10:16 PM   #2
blue 72 gmc 4x4
Registered User
 
blue 72 gmc 4x4's Avatar
 
Join Date: Jul 2009
Location: flagstaff, AZ
Posts: 387
Re: 1956 Napco GMC

First off I believe all GMC's these years came with pontiac motors in them. So if you have a chevy motor then its a swap. The original motor mount should be right under the timing cover and instead of there being mounts on the trans, the mounts were on the bellhousing. As for the 100 that means half ton.
__________________
1955 GMC Hydramatic
1959 Chevy Spartan 100
1972 Chevy Cheyenne
1972 GMC suburban
1972 GMC pickup..old blue

1955 GMC hydramatic build
http://67-72chevytrucks.com/vboard/s...d.php?t=429417

blue 72 gmc 4x4 is offline   Reply With Quote
Old 04-25-2012, 11:08 PM   #3
OrrieG
Registered User
 
OrrieG's Avatar
 
Join Date: Jun 2006
Location: Idaho
Posts: 6,604
Re: 1956 Napco GMC

Do some research here: http://www.napco4x4.org/history.htm

Transfer look right, but the front axle should have NAPCO cast into the tube next to the differential housing. Could be the front axle was swapped out at sometime.
__________________
1959 Chevy Short Fleetside w/ 74 4WD drive train (current project) OrrieG Build Thread
1964 Chevelle Malibu w/ 355-350TH (daily driver)
Helpful AD and TF Manual Site Old Car Manual Project
OrrieG is offline   Reply With Quote
Old 04-26-2012, 06:30 AM   #4
OKGMC4
Registered User
 
OKGMC4's Avatar
 
Join Date: Oct 2009
Location: Broken Arrow, OK
Posts: 735
Re: 1956 Napco GMC

I'd have to look at mine (also 56 gmc) later today but I think mine says 140hp on the vin plate and it was a straight 6 hydramatic truck. I think the 180 hp is the pontiac V8. You have a chevy hood there as well.
__________________
56 GMC BUILD THREAD:
http://67-72chevytrucks.com/vboard/s...d.php?t=368649

69/67 chevy/gmc LS powered slice and dice:
http://67-72chevytrucks.com/vboard/s...d.php?t=624747

One piece window conversion Blackdiesel style:
http://67-72chevytrucks.com/vboard/s...d.php?t=366078
OKGMC4 is offline   Reply With Quote
Old 04-26-2012, 09:16 AM   #5
buggy5872
Registered User

 
buggy5872's Avatar
 
Join Date: Jun 2011
Location: North Beaver TWP PA
Posts: 739
Re: 1956 Napco GMC

Transfer case and front end appear to be correct. What do the lift blocks between the frame and rear end look like? They were special lift blocks and the u-bolt goes through 2 ears on the side of the lift block. Here is a pic of my transfer case for comparison

Last edited by buggy5872; 04-26-2012 at 09:21 AM.
buggy5872 is offline   Reply With Quote
Old 04-26-2012, 10:51 AM   #6
northerngmc
Registered User
 
northerngmc's Avatar
 
Join Date: Jan 2004
Location: Fort Smith NT Canada
Posts: 2,299
Re: 1956 Napco GMC

Quote:
Originally Posted by blue 72 gmc 4x4 View Post
First off I believe all GMC's these years came with pontiac motors in them. So if you have a chevy motor then its a swap. The original motor mount should be right under the timing cover and instead of there being mounts on the trans, the mounts were on the bellhousing. As for the 100 that means half ton.
This may be true for US GMC Trucks but Canadian GMC trucks had Chevrolet engines, the same as Chevrolet trucks. So maybe it originated in Canada?
__________________
Blaine
59 GMC 9314 a.k.a. Whoopee
68 C20 50th Anniversary a.k.a. The Rat

http://www.flickr.com/photos/northerngmc/
http://www.members.tripod.com/P-wee/index_032.htm

1.61803 is one H of a lot better than 3.14159, no really it is!
northerngmc is offline   Reply With Quote
Old 04-26-2012, 02:45 PM   #7
1project2many
Registered User
 
Join Date: Mar 2012
Location: Lakes Region NH
Posts: 750
Re: 1956 Napco GMC

GMC here in the US did use Pontiac powerplants. I owned a 56 for a while with an original 2bbl 316 CI engine. The Chevy V8 available in '56 was the 265 rated at 155 HP while the Pontiac / GMC "317" was rated at 180 hp. Judging by the door plate that truck was equipped with the Pontiac / GMC engine.

HTH

Last edited by 1project2many; 04-26-2012 at 03:07 PM.
1project2many is offline   Reply With Quote
Old 04-26-2012, 07:17 PM   #8
72JimmyDiesel
Registered User
 
Join Date: Oct 2008
Location: Newberg OR
Posts: 7
Re: 1956 Napco GMC

This truck looks to be slightly a bubba conversion. I'm judging it by the way the transfer case is hung. Napco used a bracket above the t-case that bolted to the crossmember. The data tag on line built napco's had a gvw of 400lbs greater than the 2wd trucks. It would read 7300 and also 100 were 1/2t and 150 would be a 3/4T. I have several Napcos.
__________________
72 GMC SWB 6.2 diesel 4spd 3.07
72JimmyDiesel is offline   Reply With Quote
Old 04-26-2012, 09:54 PM   #9
Bo Duke
Registered User
 
Bo Duke's Avatar
 
Join Date: Feb 2010
Location: Lincoln, NE
Posts: 31
Re: 1956 Napco GMC

Thanks everyone, there's some good info here.

Quote:
Originally Posted by OrrieG View Post
Do some research here: http://www.napco4x4.org/history.htm

Transfer look right, but the front axle should have NAPCO cast into the tube next to the differential housing.
Thanks for the link, I'll check it out.
The front axle has Napco has onto it, on the drivers side.

Quote:
Originally Posted by buggy5872 View Post
What do the lift blocks between the frame and rear end look like? They were special lift blocks and the u-bolt goes through 2 ears on the side of the lift block.
I don't have the truck here, and the pic I have of the lift block isn't very close up. The blocks do have bump stop pads cast into them.

Quote:
Originally Posted by 72JimmyDiesel View Post
This truck looks to be slightly a bubba conversion.
This is the direction I'm leaning. Luckily this won't be a full resto truck, so if it's not a true Napco, that's ok.
Bo Duke is offline   Reply With Quote
Old 04-26-2012, 10:50 PM   #10
buggy5872
Registered User

 
buggy5872's Avatar
 
Join Date: Jun 2011
Location: North Beaver TWP PA
Posts: 739
Re: 1956 Napco GMC

the transfer case has the correct napco mounting brackets. There are just a few extra spacers. It may be spaced down to get the correct drive shaft angles.
buggy5872 is offline   Reply With Quote
Old 04-26-2012, 11:08 PM   #11
dwcsr
Hollister Road Co.
 
dwcsr's Avatar
 
Join Date: Apr 2005
Location: Houston
Posts: 4,680
Re: 1956 Napco GMC

Its a GMC X series with a Pontiac 316 V8, made in Pontiac Mi. Long bed 3/4 ton #1045 off the line that year. Canadian GMC had a different ID plate that didn't say Pontiac Michigan, USA

The hubs are Dualmatic Twin-Lever locking hubs, period correct but not sure if they are vehicle correct. But they were an option on 3/4 and 1 ton with the HO72 axle.

I think you may have a more original drive line than you think.
__________________
Dave Chapman
Hollister Road Company
Houston Tx
www.hollisterroad.com
info@thoroco.com
713-937-0387
dwcsr is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 04:28 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Copyright 1997-2013 67-72chevytrucks.com