Rear Axle Ratio Charts For 1967 - 1972 GM Trucks

['68OrangeSunshine]

Originally Posted by badpeanut

i have a 1970 leaf-spring 6-lug 3:07 posi, which is "tpo 0422". I decode this as:

• tpo=ca 10 3.07 posi
• 0422=april 22

what is the meaning of ca vs ce?

at first i thought it might be leaf spring rear suspension vs. Coil spring rear suspension, but i see the same with k-series so this is ruled out.

CA = [2wd] ALL.
CE = '' V8
CS = '' L6
CM = '' V6

[LockDoc]

-
I just wanted to thank everyone for adding to the thread and say that I'm glad it is still helping people out.

LockDoc

[dlyons321]

This is one awesome thread! So the stamp on my axle is TPR 0612w2 E. It is decoded as either 1970 KE 10 3.07 w/ posi or 1971 G-10 3.36. The gears are 3.07 I can confirm but not with a stamp, rather an engraving where the stamp usual is. This is a 12 bolt unit.
Is the KE designated as 4 wheel drive rear end?
Any literature on decoding the casting #s on the outside of rear end? #3896839
My truck is a 1970 k10 swb. Im curious id that 12 bolt was an option on a 1/2 ton truck. The SPID does not say that. Most likely added later by previous owner?

['68OrangeSunshine]

Originally Posted by dlyons321

This is one awesome thread!
Is the KE designated as 4 wheel drive rear end?

Yes. Specifically K = 4WD [C = 2WD, but you knew that.]
E = Eight cylinders.

Other designators are -- KS, KM, KA.
S = Six cylinders [L6]
M = Six cylinders [V6]
A = All trucks.

Front wheel drive [only] was not an option in this era. All vehicles were primarily rear wheel drive. Front wheel drive assist was actuated by locking the hubs. You have to get out of the truck, stand in the mud, stoop down and twist the levers on each side to engage.

The Corporation 12-Bolt differential was standard on all 1/2 tons.
[There may have been ''Heavy Half'' variations optioned, but I won't get into that. ]

dlyons321 -- Is your truck an automatic? Manual gearshift trucks got 3.73. Automatics got 3.08.
3.36 is an unusual ratio for a pickup.
G/10s are 1/2 ton Vans iirc.

[dlyons321]

Originally Posted by '68OrangeSunshine

Yes. Specifically K = 4WD [C = 2WD, but you knew that.]
E = Eight cylinders.

Other designators are -- KS, KM, KA.
S = Six cylinders [L6]
M = Six cylinders [V6]
A = All trucks.

Front wheel drive [only] was not an option in this era. All vehicles were primarily rear wheel drive. Front wheel drive assist was actuated by locking the hubs. You have to get out of the truck, stand in the mud, stoop down and twist the levers on each side to engage.

The Corporation 12-Bolt differential was standard on all 1/2 tons.
[There may have been ''Heavy Half'' variations optioned, but I won't get into that. ]

dlyons321 -- Is your truck an automatic? Manual gearshift trucks got 3.73. Automatics got 3.08.
3.36 is an unusual ratio for a pickup.
G/10s are 1/2 ton Vans iirc.

Orange,
I understand everything other than the 12 bolt coming standard on 1/2 ton trucks. I have been under the impression that 1/2 ton got 10 bolts and 3/4 ton got the 12 bolts.
My truck is automatic and has Dana 44 with 3.07 gears in the front.

['68OrangeSunshine]

Originally Posted by dlyons321

Orange,
I understand everything other than the 12 bolt coming standard on 1/2 ton trucks. I have been under the impression that 1/2 ton got 10 bolts and 3/4 ton got the 12 bolts.
My truck is automatic and has Dana 44 with 3.07 gears in the front.

You may have it backwards. Some 3/4 ton diff had 10 bolts and the FF had 14.
Later than 67-72, S/15s had 10 bolt diffs, but that was coincidental and another type.
The 12-Bolt Truck rearend was different from the 12-Bolt Car diff, too.
I'm not expert on the EATON and HO52 rears. They were 3/4 ton iirc.

[dlyons321]

ahhhh I got it now. I apologize I'm a recovering square body guy. I bought this truck in July and I'm just now getting some real time with it. Thanks for your help!

[pjmoreland]

The axle code that's on my 1971 K10 is not listed for some reason. The code is TAZ. It is 3.73 with posi, and it is listed on the SPID. The date code cast into the housing is I 12 0, or September 12th, 1970.

[VWNate1]

SWEET ~ that's the rear end I'd love to find .

[LockDoc]

Originally Posted by pjmoreland

The axle code that's on my 1971 K10 is not listed for some reason. The code is TAZ. It is 3.73 with posi, and it is listed on the SPID. The date code cast into the housing is I 12 0, or September 12th, 1970.

There have been a few that haven't been listed. If the charts had been typed out it would be easy to add them but I got all of them as *.jpg files so it might be a little tough to do. I might try adding that to the bottom of the list in the 1971 picture and see what happens.

[LockDoc]

Originally Posted by pjmoreland

The axle code that's on my 1971 K10 is not listed for some reason. The code is TAZ. It is 3.73 with posi, and it is listed on the SPID. The date code cast into the housing is I 12 0, or September 12th, 1970.

I added that one to the list for '71.

[pjmoreland]

Originally Posted by LockDoc

I added that one to the list for '71.

Nice! Thank you

[RichardJ]

After 50 plus years do the stamped codes really mean anything. My '67 had 4.56 gears with a open diff. About 15 years ago, I installed 3.54 gears with posi carrier I took out of a '80s Dodge Dana. The code/ numbers on the axle have the wrong info.

[LockDoc]

Originally Posted by RichardJ

After 50 plus years do the stamped codes really mean anything. My '67 had 4.56 gears with a open diff. About 15 years ago, I installed 3.54 gears with posi carrier I took out of a '80s Dodge Dana. The code/ numbers on the axle have the wrong info.

I'm sure many of them have been modified over the years but I would say that the majority of the ones that have been changed have been changed as a whole unit and that would retain the integrity of the code.
.

[VWNate1]

Way back when I was a dealer mechanic we were told to always obliterate the stamped in codes whenever we did a change of the internals .

[LockDoc]

Originally Posted by VWNate1

Way back when I was a dealer mechanic we were told to always obliterate the stamped in codes whenever we did a change of the internals .

That certainly makes sense. I'm betting most of the small shops didn't follow that policy. I have a friend here in town that has done quite a few of them. I will have to ask him about it.

[pjmoreland]

Originally Posted by LockDoc

I added that one to the list for '71.

Good evening, Leon. I'm afraid I made a mistake on my TAZ rear end axle code and thinking it had 3.73 gears. I have disassembled both differentials now on my truck, and it is obvious that someone has been through them at some point due to the presence of non-factory shims. After reading through the 1971 sales brochure, I see that trucks optioned with a 350 engine came standard with 3.07 gears, in which case 3.73 gears would be an option that would be listed on the SPID. '68OrangeSunshine confirmed this today with an example of his '71 Jimmy that has a 350 engine and has 3.73 printed on his SPID. My SPID lists Positraction, a 350 engine and a 4 speed transmission, but it doesn't list the axle gear ratio, so it had to have been a 3.07. It's still odd that my TAZ axle code isn't in the table, and there is a listing for a 3.07 posi rear end in the table.

I'm sorry I made extra work for you unnecessarily.

[VWNate1]

Originally Posted by LockDoc

That certainly makes sense. I'm betting most of the small shops didn't follow that policy. I have a friend here in town that has done quite a few of them. I will have to ask him about it.

Sadly more than a few dealer guys are parts changers and flat refused to do this leading to problems on down the line .

Common sense, isn't .