Rear Axle Ratio Charts For 1967 - 1972 GM Trucks

[LockDoc]

Originally Posted by fist5366

So is this out of a 70 with posi I was told it was out of a blazer with 3.73 gears. It was in the truck when I got it if I remember right we pulled and checked gears but that was 20 yrs ago . I'm sure they could have been changed at some point

TPR..... It shows that code for a '70 KE-10, 3.07:1 ratio and a '71 G-10, 3.36:1 ratio.

Yep, in 40+ years anything is possible.

LockDoc

[garyd1961]

Thanks for posting this but I have a question. My axle code is TDE which just shows 3.07 gears. I thought my rear TDE was posi traction. The rear is not in the truck but if I lock one axle and the yoke in place the other axle will not turn. I thought this meant posi traction.

[fist5366]

Thanks this is all great info

[LockDoc]

Originally Posted by garyd1961

Thanks for posting this but I have a question. My axle code is TDE which just shows 3.07 gears. I thought my rear TDE was posi traction. The rear is not in the truck but if I lock one axle and the yoke in place the other axle will not turn. I thought this meant posi traction.

Use a floor jack and lift both rear tires off the ground. Spin one tire. If both tires turn the same direction you have posi if one tire moves forward and one backward you have an open rear end.

LockDoc

[garyd1961]

Originally Posted by LockDoc

Use a floor jack and lift both rear tires off the ground. Spin one tire. If both tires turn the same direction you have posi if one tire moves forward and one backward you have an open rear end.

LockDoc

The rear isn't in my truck but it turns one axle opposite of the other. I know it's an open rear now and I have been looking at an Eaton Truetrac. I plan to put the open rear in for now and to rebuild the one I'm taking out latter.

[fist5366]

This might be a stupid question be where exactly do measure from to compare to the stock rear end . I can find a width online and I tried to measure but it's a pain cause it's in the truck.

[LockDoc]

Originally Posted by fist5366

This might be a stupid question be where exactly do measure from to compare to the stock rear end . I can find a width online and I tried to measure but it's a pain cause it's in the truck.

I believe it is from flanges where backing plates bolt on. It can be tough when they are still in the truck....

LockDoc

[jcwren]

Having a RAY code, that's a 1972 KE 10 3.07 open rear end. There's a letter in front of the 251. It's very faint, and looks like a W, which would mean it was built in Warren, MI. 251 would be September 7th (the Julian date, which is the day of the year), and the 1 is the 1st shift.

[Romo912]

My 67 gmc starts with a HA
Posted via Mobile Device

[LockDoc]

Originally Posted by Romo912

My 67 gmc starts with a HA
Posted via Mobile Device

That would be the 3.73 ratio non-posi then.

LockDoc

[OregonNed]

Interesting and helpful thread. I'm currently having the rearend in my '68 rebuilt due to many many issues of wear and the cross pin bolt was broken and barely hanging on. I have not sought out the stamped code on the axle housing, but It does have a 3.07, open carrier in it. Along the ring gear are the numbers to confirm the ration, as well as "72" stamped on it. Would this indicate gear possibly transplanted from a 72?

[LockDoc]

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I don't think they were date coded but I'm not 100% sure about that.

LockDoc

['68OrangeSunshine]

Originally Posted by LockDoc

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I have saved these from different places so they don't match each other. I saved them as image files and they are all different resolutions and sizes. They really need to be typed into a document file so the size and style of font matches on all of the charts. Unfortunately I don't type good enough to do that so we will try it this way. I just hope they are all readable with the image size restrictions for the board. I think I have them sized close to the maximum that the board allows. Disregard the C14 designation in the '67 chart, it should be C10.

In case someone is thinking Photobucket or some other photo hosting service, I won't do that for two reasons. One, I am not going to sign up for an account & Two, If the photobucket account is ever closed the thread will be worthless because their won't be any pictures of the charts in it, just empty boxes ...

Thanks.

LockDoc

Subscribing

[sfont66]

Very good info
Subscribed

[factorystock]

The charts do indicate what GM offered, but, GM could have offered more ratios to fill the bill more precisely. We had to wait for the square body years for the 3.42 ratio for C 10's and the 3.73 ratio for C 20's.

['68OrangeSunshine]

I ran the numbers on 2 differentials I have.
One, [TPF 1204w] which I had on my '68 C/10 Stepside, but was damaged in a side impact collision, I thought we pulled off a '69 GMC shortbed fleetside. It had been under my Stepside since the Mid '80s. 3.73 Eaton posi. Chart says 1970, not '69, but who can tell the years by looking at a GMC?
The diff I replaced it with [HR 0316w] is [going by the charts] off a '67 P/10 4.11 open.
It was a longbed because the 5' handbrake cables didn't work on my 115'' wheelbase C/10. The guy who sold it to me said it came off a '65 or '66 truck. I had it rebuilt with new axles, bearings and 3.73 gears. Still breaking it in.

[pjmoreland]

The rear end that was in my truck when I bought it was one of the wider units from a 1970. It had 1970 written on it in yellow paint marker, probably from a wrecking yard. It also measured at the wider width found on 70-72 rear ends. Code stamped on the top of the passenger side axle tube was TDA 11 06 W2, which translates to 1970 3.73 built November 6th. There was also a date code cast into the differential housing that read J 31 9 which translates to October (J) 31st, 1969, which would be appropriate for an early-built 1970 model year.

[pjmoreland]

I purchased a replacement rear end that had the following codes:

HA 05 06 W = 1967-69 3.73 May 6th
D 17 8 = April 17th, 1968

The odd thing is that I pulled it out of a 1967 Suburban. I'm guessing it wasn't the original rear end though due to the date code on the differential casting. The cool thing is that it is a reasonable date for my '68 truck that was built in the summer of '68.

[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.

['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]

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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.