Rear Axle ID

[76StepSd]

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.

[Irish_Alley]

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

[76StepSd]

Here ya go

[76StepSd]

Sorry had to rotate it 90.

[Irish_Alley]

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

[76StepSd]

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


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[76StepSd]

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.

[JohnnyPopper]

How many lug nuts do your rear wheels have?

[76StepSd]

5 lugs


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[JohnnyPopper]

Odd, C20's usually have 8 lugs.

Maybe the brain trust can answer if C10 and C20 rear brake components are interchangeable?

[wz7u]

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?

[76StepSd]

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.


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[JohnnyPopper]

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?

[wz7u]

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.

[Irish_Alley]

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).