Rear Axle Ratio Charts For 1967 - 1972 GM Trucks

[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

[fist5366]

Thanks I'm just trying to figure out what it's out of. It seems wide but when I measured today it was pretty close to 60" which makes me wonder why it seems so tight. I was told it was out of a 76 blazer but now I have no clue, it is 6 lug

[5 Driver]

If the truck has posi-traction, would it most likely be listed as an option on the SPID?

[LockDoc]

Originally Posted by 5 Driver

If the truck has posi-traction, would it most likely be listed as an option on the SPID?

Sorry, I missed this somehow....

Normally they would be an option and listed on the SPID, unless it was added later by someone. The posi rears also had a plastic tag on the fill plug with instructions to use positraction fluid in them. That could be missing though.

LockDoc

[5 Driver]

Originally Posted by LockDoc

Sorry, I missed this somehow....

Normally they would be an option and listed on the SPID, unless it was added later by someone. The posi rears also had a plastic tag on the fill plug with instructions to use positraction fluid in them. That could be missing though.

LockDoc

No apology needed.
Thats what I thought...wishful thinking I guess.
Thanks,

[JDSurge]

Thanks guys for showing the axle charts. My Blazer was a RAW, so 3:73 is the axle ratio but what about the numbers stamped to the right of the RAW? Mine is W (then what looks like the upper part of a '3' ) 47
So W 347 ?
Thanks.

[davischevy]

Here is the stamp on my rear axle. RAY for 3.07 open. I'm going to guess it was built on the 251st day of the year, 1st shift.

[LockDoc]

Originally Posted by davischevy

Here is the stamp on my rear axle. RAY for 3.07 open. I'm going to guess it was built on the 251st day of the year, 1st shift.

Larry,

I always thought it would be the 25 day of the 1st month. Don't know for sure.

LockDoc

[davischevy]

Where is Keith Seymore when we need him?

[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

[70cst]

Great info ... Thanks

['68OrangeSunshine]

Originally Posted by LockDoc

-
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.