Author Topic: Rear Axle ID  (Read 2737 times)

Offline 76StepSd

  • Registered Users
  • *
  • Posts: 123
Rear Axle ID
« on: March 12, 2022, 06:47:28 PM »
I got a 76 stepside but....the guy i got it from had to replace a number of driveline items...i.e. engine...trans.....rear end..lol. Oh yeah some major replacing went on  but i am just trying to find out what rear axle ratio i have. I believe the axle date is August 17 1978 but you can correct me if i am wrong but what was stamped on the tube was

   KAS 074W91   that is what i am mainly concerned about. Any info would be greatly appreciated.
« Last Edit: March 12, 2022, 06:49:54 PM by 76StepSd »

Offline Irish_Alley

  • Tim
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 13319
  • Family is not an important thing. It's everything.
Re: Rear Axle ID
« Reply #1 on: March 12, 2022, 10:42:14 PM »
ive never really been able to find anything off the stamped numbers. for the most part if you post a picture of the housing then we can tell you what years they came in and for the most part all parts are interchangeable within those years
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline 76StepSd

  • Registered Users
  • *
  • Posts: 123
Re: Rear Axle ID
« Reply #2 on: March 12, 2022, 11:25:08 PM »
Here ya go

Offline 76StepSd

  • Registered Users
  • *
  • Posts: 123
Re: Rear Axle ID
« Reply #3 on: March 12, 2022, 11:29:28 PM »
Sorry had to rotate it 90.

Offline Irish_Alley

  • Tim
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 13319
  • Family is not an important thing. It's everything.
Re: Rear Axle ID
« Reply #4 on: March 13, 2022, 09:44:24 AM »
alright, well its obvious that its a 12 bolt and the guessing comes from the stamped codes you showed. im finding 3.07 (stock ratio but could be changed) Jb5 brakes and came in the years 78-79 ½ton 4x2 non-locking
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline 76StepSd

  • Registered Users
  • *
  • Posts: 123
Re: Rear Axle ID
« Reply #5 on: March 13, 2022, 10:17:50 AM »
Thank you for the info I have alot of work to do on the truck and the axle area will be part of it. Pinion seal is leaking also …so I plan on a freshening up of it  amongst other things


Sent from my iPhone using Tapatalk

Offline 76StepSd

  • Registered Users
  • *
  • Posts: 123
Re: Rear Axle ID
« Reply #6 on: March 14, 2022, 06:53:14 PM »
Also I remember buying rear shoes for the truck some time ago and the shoes that the guy brought out were too small and when he finally brought out shoes that matched the old ones he said they were listed as C20 shoes.

Offline JohnnyPopper

  • Senior Member
  • ****
  • Posts: 2560
  • Old Goof
Re: Rear Axle ID
« Reply #7 on: March 15, 2022, 11:25:18 PM »
How many lug nuts do your rear wheels have?
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline 76StepSd

  • Registered Users
  • *
  • Posts: 123
Re: Rear Axle ID
« Reply #8 on: March 16, 2022, 03:14:20 PM »
5 lugs


Sent from my iPhone using Tapatalk

Offline JohnnyPopper

  • Senior Member
  • ****
  • Posts: 2560
  • Old Goof
Re: Rear Axle ID
« Reply #9 on: March 16, 2022, 08:25:22 PM »
Odd, C20's usually have 8 lugs.

Maybe the brain trust can answer if C10 and C20 rear brake components are interchangeable?
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline wz7u

  • Newbie
  • Posts: 39
  • Old, tired - like the truck
Re: Rear Axle ID
« Reply #10 on: March 17, 2022, 03:12:48 PM »
I do not believe they interchange, like c20 drums on c10 shoes. I suppose one could try, but you definitely aren't going to use c20 drums on a c10 axle - how are you going to accommodate the wheel bearings?
'79 C20 454/th400 "Pearl"

Offline 76StepSd

  • Registered Users
  • *
  • Posts: 123
Re: Rear Axle ID
« Reply #11 on: March 17, 2022, 05:28:05 PM »
Interesting ….maybe the guy at the parts counter misread but I do know that the axle was not the original…..I do think the truck qualifies as a Big 10 possibly….it is a 6050.


Sent from my iPhone using Tapatalk

Offline JohnnyPopper

  • Senior Member
  • ****
  • Posts: 2560
  • Old Goof
Re: Rear Axle ID
« Reply #12 on: March 17, 2022, 05:35:30 PM »
I do not believe they interchange, like c20 drums on c10 shoes. I suppose one could try, but you definitely aren't going to use c20 drums on a c10 axle - how are you going to accommodate the wheel bearings?

I thought the same thing but wondered of you could change out the backing plate but no- the C20 axle has 8 lugs, no?
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline wz7u

  • Newbie
  • Posts: 39
  • Old, tired - like the truck
Re: Rear Axle ID
« Reply #13 on: March 17, 2022, 09:47:44 PM »
IIRC, (which I often do not), the two platforms do not interchange. Perhaps you could get 1/2 ton shoes to work on a 3/4 ton backing plate, but the shoes would be narrower than is allowed. Without spending some time on a parts house webpage comparing part numbers, I'm going to guess some of the parts interchange but I wouldn't stake my stopping ability on it. I do remember something about heavy halfs using a hybrid setup of sorts, (wider shoes) but again, without playing parts guy I really can't say 100%.

Yes, C-20 has 8 lugs, where C-10 had 5 and, I think, a 6 lug version in newer rigs. I imagine one could change out the backing plates for 3/4 T, but I doubt its viable.

'79 C20 454/th400 "Pearl"

Offline Irish_Alley

  • Tim
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 13319
  • Family is not an important thing. It's everything.
Re: Rear Axle ID
« Reply #14 on: March 19, 2022, 10:11:15 AM »
½ tons can come with a few different brake shoes just like ¾ and 1 tons (jb1, jb3, jd3, jd5 and jb5. the "D" denotes for diesel engines since they have lower vacuum). JB1 was the basic manual brakes for light duty trucks 4300 LBS. JB3 was for the lightest power brakes you could get 4600 LBS and JB5 was for the heavier ½ tons 6400 LBS. the JB1 and 3 share the same brake shoes while the JB5 has its own size but they share the same rear shoes as the JB6 (found in ¾ tons). on a side note the "big ten" had a gvwr of 6050lbs while the ½ tons normally stayed at 6000 or below (4900).
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes