The Stovebolt Site Forums The Shop Area General Truck Talk Differences between second series '55 and '56 GMC

I have a '56 GMC model 150 that may be a 1955 titled as a 1956. I have been consulting with an automotive /truck historian, and that is the conclusion he is coming to, and I agree. My truck has the '55 trim pieces between the front bumper ends and the upper trim ends with the park lamps. (which is where my questions started) My hood emblem and side emblems are chrome, not painted white as in 56, the truck has two piece 15" rims, all 4 the same with 55 stamped on the pieces- in 1956, the industry went to tubeless tires and 17.5 inch rims to avoid problems with putting tubeless tires on tube rims, and my truck was originally 6v with the pedal starter (which it still has- was converted to 12v. 6 volt was phased out in 1956. Are there any other differences folks know about? Also, my truck has a 270 small port six, four on the floor with compound low, and vacuum powered wipers.

https://picasaweb.google.com/102896607746579210671/Motor_2012
https://picasaweb.google.com/102896607746579210671/November152012

your picture links don't work...

Thanks- the privacy settings were too high- should work now.
Dave

"page not found" is the Picasa problem

your 'historian' shouldn't have to think too hard to know that back then vehicles were not titled by model year, but by the year of first registration ... question comes up regularly here .... doesn't the truck have any id tags on it?

Bill

A 1955 serial number will start with 152Y. A 1956 number will start with 152X.

A 1955 originally came with a 248, a '56 with a 270.

ref. http://www.oldgmctrucks.com/photos/SN_150_Series_YXTS.jpg

My serial # is 152PYxxxx. I have the 4 speed SM 420 with the compound low, no reason to think the 270 is not original, except the serial number clearly indicates it is a '55, and 270 was not a 1955 option.

Dave

Are the photo links working?

Dave

A Y serial number would make me suspect the 270 is not original.

Yes, and that would explain why the rings are in good shape for 94,000 miles.

1956 GMC's did have chrome emblems. 1955 left over units were used "half built" and finished as 1956. Seen several, had one. 1955 GMC 2nd series, Task Force, Blue Chip truck released mid year was 12V on the optional Pontiac V8 and 6V on the 6 cyl, then in 1956 all were 12V as you say. The 1/2 T had 6.70 x 15 Tubeless tire on a one piece wheel. I think split rims were on 3/4 T and up. The 6 cyl was a 248 in 1955 but if built as a 56, that would be your 270. Don't forget that in the past 57 years, previous owners can add/change engine, transmissions, front clips, rear ends, emblems and all manner of parts from different years and models creating a hybrid. All the 1/2 T had 6 lug wheels, 3/4 T had 8 lug. (I believe there was a 15" two piece wheel and a 17" three piece wheel, both Kelsey-Hayes)

Bartamos-

Do you know if the serial number on the one you had indicated 1955 or 1956? The Y or X as mentioned above.

Dave

It was 56 and had a Y serial. There are some ways to tell a half built (Your under turn signal trim is 55 as you know) I think the voltage regulator is on the firewall on 55 and the inner fender on 56, or visa versa, also I believe 56 had a "hand clearance", wide, dimple on the cross bar so as to get better access to the hood release. The 55 was straight. As Red58 said, they were often titled in a different year. There are "half built" trucks and there are pure trucks. I have only seen this in 55-56, possibly because of the late release of the 55.2 and they wanted to hurry up and switch to new engines and all 12V for parts commonality. I am not sure about 3/4 ton models. Many times, in dating parts, a stamp showing previous year is proof that it is for the following year because they made the parts, and vendors made the parts, in time for the build and sales in Sept/Oct of the preceding year of the model year.

It may well have been originally titled in '56 but a Y series is a '55 model.

Yep.

My historian is Jim Wagner, who wrote GMC Light Duty Trucks as well as GMC Heavy-Duty Trucks, 1927-1987. The first is a very detailed history, with a '56 on the cover, and I have not read the second one. My guess is it is as good as the first. He caught on right quick to the title year vs. year of manufacture issue. I had given him limited info at first, and once I gave him all the details he came right back with '55 titled in '56. I did not want to mention his name without his permission.

I have a 55 gmc and I believe that a 270 engine WAS an option for the year 1955. reason being is that whomever first titled the truck, (a local lumberyard I think) they titled the truck using the engine number. and I still have that engine in my truck.

Whether a 270 was offered or not, the proper procedure when changing an engine in a truck titled by engine number is to get the title changed. That could be what happened in your case.

interesting