The Stovebolt Site Forums The Shop Area Driveline rear end ID

hi, i'm woring on my 1951 3100 panel and i'm replacing the pinion seal and i'm trying to figure out what rear end is in it. its a 10 bolt oval shape with a drain plug in the cover. there is a stamped number, NK1011 on the passenger sida and a cast 273 on the drivers side.
also, i need a pinion shaft bolt. any suggestions where i may find one?
thanks

Original 1951 3100 1/2 ton axles Do Not have a pinion seal.
Original 1951 3100 1/2 ton trucks came with a propeller shaft inside a torque tube, which is also called a enclosed driveline or driveshaft.
There is only one u-joint inside a torque tube, located at the end of the transmission.
The pinion splines are inserted into the propeller shaft and is dowel pinned in place. Picture

Torque Tube parts illlustration

3/4 ton trucks and up all had open driveshafts
1-1/2 Ton Rear Axle parts illustration

Someone must of replaced the original enclosed drive line with a open driveshaft drive or (Hotchkiss Drive)
Open driveshaft carriers do have a pinion oil seal at the rear u-joint axle connection.

NK1011 and 273 do not show in the 1950 Chevrolet Restoration Pack Go to pdf page 6 for rear axle numbers

You are in luck I found NK1011 in the 1955 Chevrolet Truck 1st Series Restration Pack Go to pdf page 6 for rear axle numbers.

Rear Axle Numbers
NK1011
N = Year, 1955 1st series
K = Type and Assembly Plant
K = Type, 3100, 3.9 ratio
K = Assembly Plant, Detroit
10 = Month, October
11 = Day of the month, 11th

Axle was manufactured on, October 11th, 1955 at the Detroit, Michigan GM Assembly Plant,
Axle has a 3.90 ring and pinion gear ratio
Axle was manufactured to go into a 3100 1/2 ton 1955 1st series truck

Someone swapped the drive train in your 1951 3100 truck with a 1955 1st series truck 3100 drive train.
They also changed or changed out the transmission to except a open drive shaft.
1955 1st series is when Chevrolet stopped using the torque tube drive line on trucks.

wow, thanks for all info. that was very helpful. the truck has a 1957 235 in it so the drive train must have been switched at sometime. i'll have to check the tranny numbers to see if that has too.

tried to view your panel but couldn't pull up the pics from photo bucket. since you have a panel you may know this.
i have some rot in the back corner pass the rear wheel well on the drivers side. almost looks like a regular cab corner may work. does anyone sell the body panels for a panel truck or am i on my own?

thanks again.

"does anyone sell the body panels for a panel truck"

Stovebolt Forums Has a Panels 'N Burbs forum, just recently there was a person asking the same question..
Here is the thread Underside rear-cabin corner photos needed

Here are some links that are in the above thread.
Jim Carter's listings has the 1947-1955 Suburban, Panel, and Canopy Express Rear Cab Corner .

tclederman has a page on his 1954 Suburban website, it shows some corner Repair Photos.

1947-1955 1st series Suburban, Panel, and Canopy Express single bodies are virtually the same.
The one ton Panel, and Canopy Express bodies are longer.
----------------

As far as your drivetrain, my hunch is they installed 1957 235 with its open drive shaft TRANNY (bottom trans.). and made a custom drive shaft.
I think they had to use the 1951 bell housing and may had to use a 3 or 4 speed rear tranny mount cross member.
When you swap from a closed to a open driveline you also have to change out the rear leaf springs. (You can flip the leaf spring too)
The open driveline axle housing is solid mounted to the rear leaf springs.
The closed driveline axle housing is mounted to the rear leaf springs using a spring seat with a center bushing.
The spring seat and bushing allows the closed driveline torque tube to swivel when the leaf springs compress.
The closed driveline axle has ears welded on the housing to accept the spring seat which is u-bolted to the leaf springs.
The closed driveline axle rear leaf spring stack center pin is off set to the front.
The open driveline rear leaf springs stack center pin is positioned in the center of the leaf spring.
1947-1954 Rear Spring Alignment .

There wasn't many of the 1955 1st series rear axles made and there is a
1955 1st series Supplement to the 1954 Chevrolet Truck Shop Manual (I cannot find a free one online).
The 1955 1st series Supplement to the 1954 Chevrolet Truck Shop Manual talks primarily about the axle you have. There are 13 pages.

The 1955 1st series Chevrolet Trucks where sold from, September 1954 to March 1955 about 6 months.