12 Bolt ID - The 1947 - Present Chevrolet & GMC Truck Message Board Network

crakarjax · 09-16-2014, 09:31 AM

I have two 12-bolt rearends, one from a '72 and another that I got just to use the axles and possible the 3.42 gearset. I pulled the codes off of the tubes and was looking around for ID charts or something but couldn't find any! Mainly I noticed that the parts rear seems to have a beefier yoke and I was thinking of using it since I'm rebuilding the rear anyway, but I'd like to know what U-joint it uses.

Can anyone decode these and/or tell me how to do so myself?

KDA W197 1
THA W148 2

*Fitz* · 09-16-2014, 11:19 AM

Quote:

Originally Posted by crakarjax

I have two 12-bolt rearends, one from a '72 and another that I got just to use the axles and possible the 3.42 gearset. I pulled the codes off of the tubes and was looking around for ID charts or something but couldn't find any! Mainly I noticed that the parts rear seems to have a beefier yoke and I was thinking of using it since I'm rebuilding the rear anyway, but I'd like to know what U-joint it uses.

Can anyone decode these and/or tell me how to do so myself?

KDA W197 1
THA W148 2

The first one is an oddball but the second appears to be a 3.73 ratio open carrier diff assembled at Tonawanda.

Are you sure that KDAW1971 is a truck housing? My friend, Chevelle Dave, insists it's a 68 chevelle diff with 2.73 ratio and an open carrier.

crakarjax · 09-16-2014, 11:31 AM

Quote:

Originally Posted by Fitz

The first one is an oddball but the second appears to be a 3.73 ratio open carrier diff assembled at Tonawanda.

Are you sure that KDAW1971 is a truck housing? My friend, Chevelle Dave, insists it's a 68 chevelle diff with 2.73 ratio and an open carrier.

These are both certainly truck 12 bolts! And one is a 3.08 open spring, the other a 3.42 open leaf -- and I'm not saying that the gears weren't swapped at some point but they are def. stock GM gears, and definitely look as old as the housings. There are some other numbers on the pumpkin, I could get those tonight if it would help?

Sklptrljay · 09-16-2014, 02:04 PM

I found the one stamped THA as a open 3.08 from a 1971 c10. I don't see any rear end from 67-72 that starts with a K. Are you positive about the first 3 letters?

crakarjax · 09-16-2014, 03:09 PM

Quote:

Originally Posted by Sklptrljay

I found the one stamped THA as a open 3.08 from a 1971 c10. I don't see any rear end from 67-72 that starts with a K. Are you positive about the first 3 letters?

I am sure about the letters, but I am not positive that it is 68-72 -- I bought it on craigslist and it looks quite a bit better than the rear that I have. If I recall it may have been out of a mid-80's truck?

*Fitz* · 09-16-2014, 09:13 PM

Quote:

Originally Posted by crakarjax

These are both certainly truck 12 bolts! And one is a 3.08 open spring, the other a 3.42 open leaf -- and I'm not saying that the gears weren't swapped at some point but they are def. stock GM gears, and definitely look as old as the housings. There are some other numbers on the pumpkin, I could get those tonight if it would help?

If you know what they are why ask the board what they are?

**Ol Blue K20** · 09-17-2014, 08:11 AM

How about pics..can't be from the 80s. They were 10 bolts by then.

snipescastle2 · 09-17-2014, 08:17 AM

could that rearend be from a '64 or '65? they look almost indentical, try looking up the axles codes for those years......I bought a 1964 12 bolt, the track bar bracket mount was welded to the the axle tube -vs. a stud in the top of the housing.
Hope this helps.....
Ben

crakarjax · 09-17-2014, 08:48 AM

Quote:

Originally Posted by Fitz

If you know what they are why ask the board what they are?

I don't know what year or model they are from, that's what I'm curious about.

Quote:

Originally Posted by snipescastle2

could that rearend be from a '64 or '65? they look almost indentical, try looking up the axles codes for those years......I bought a 1964 12 bolt, the track bar bracket mount was welded to the the axle tube -vs. a stud in the top of the housing.
Hope this helps.....
Ben

Actually this one has no track bar mount at all -- it is missing the top of the housing stud and I didn't see one welded to the tube either.

This site indicates that the 12 bolt went through 1987, at least on some applications.

snipescastle2 · 09-17-2014, 09:45 AM

I'll post a picture of mine, I removed the track bar mount, ground down the welds, powder coated it, but I'd bet that's the one you have, does it have coil spring perches on the axle tubes?
Ben

snipescastle2 · 09-17-2014, 10:36 AM

Here's mine:

hope this helps....
Ben

crakarjax · 09-17-2014, 11:05 AM

Quote:

Originally Posted by snipescastle2

Here's mine:
hope this helps....
Ben

That looks really nice! But no, mine has leaf mounts.

bruceman1968 · 09-17-2014, 11:34 AM

Quote:

Originally Posted by crakarjax

Can anyone decode these and/or tell me how to do so myself?

KDA W197 1
THA W148 2

KDA = 1975-79 C10 3:42 open, or 1981 K10 3:42
W = Warren
197 = Julian Date, July 16th
1 = 1st Shift

THA = 1971 c10 3:07 open
W = Warren
148 = Julian Date, May 28th
2 = 2nd Shift

You need a date code for the KDA axle. Can't tell you where on the axle to look, but your looking for a letter followed by 3 numbers. Ex. A123

crakarjax · 09-17-2014, 11:46 AM

Quote:

Originally Posted by bruceman1968

KDA = 1975-79 C10 3:42 open, or 1981 K10 3:42
W = Warren
197 = Julian Date, July 16th
1 = 1st Shift

THA = 1971 c10 3:07 open
W = Warren
148 = Julian Date, May 28th
2 = 2nd Shift

You need a date code for the KDA axle. Can't tell you where on the axle to look, but your looking for a letter followed by 3 numbers. Ex. A123

Awesome, thanks! I think I'm going to be using this rear (originally just got it for the axles) so I'll keep an eye out for that code when I clean it up and post back here when I find it.

crakarjax · 09-21-2014, 11:41 PM

So the gears indicate 1974. Couldn't find any code as mentioned though. Still looking for the yoke application but I'll probably just measure it to figure out the proper u-joint.

68Gold/white · 09-22-2014, 12:54 PM

Quote:

Originally Posted by Ol Blue K20

How about pics..can't be from the 80s. They were 10 bolts by then.

Parts books I used in past list 82 as last year for 12 bolt. Not posting to argue, just saying. I've seen very few 12 bolts in 80's pickups

crakarjax · 10-01-2014, 09:50 PM

I measured the yokes, and while I thought that the yoke from the '74 was a 1350 yoke it looks like it is a 1330 yoke. The '71 yoke is a 1310 yoke, and seems to be in pretty good condition so I'm going to use that. The 1330 would have needed a sleeve and straps anyway so that works out I guess. The 1330 is a lot beefier at the pinion splines though, as you can see in the pictures -- and is a bit taller.

09-16-2014, 09:31 AM	#1
crakarjax Registered User Join Date: Dec 2009 Location: Kirkland, WA Posts: 1,302	12 Bolt ID I have two 12-bolt rearends, one from a '72 and another that I got just to use the axles and possible the 3.42 gearset. I pulled the codes off of the tubes and was looking around for ID charts or something but couldn't find any! Mainly I noticed that the parts rear seems to have a beefier yoke and I was thinking of using it since I'm rebuilding the rear anyway, but I'd like to know what U-joint it uses. Can anyone decode these and/or tell me how to do so myself? KDA W197 1 THA W148 2 __________________ 1968 LWB C20 / AC / Wood Bed

09-16-2014, 02:04 PM	#4
Sklptrljay Registered User Join Date: Apr 2012 Location: Stillwater, Oklahoma Posts: 874	Re: 12 Bolt ID I found the one stamped THA as a open 3.08 from a 1971 c10. I don't see any rear end from 67-72 that starts with a K. Are you positive about the first 3 letters? __________________ 1971 C/10 SWB, 15x8 Rallys, 4.5" X 7" static drop, C-notched, 350/350, 3.73 Posi. .........A 383 and Gear Vendors are on my bucket list. 1972 GMC 4X4 K1500 Survivor - Sold No matter what problems life throws at you, your time on Earth can be incredibly fulfilling and rewarding.....if you just lower your expectations. -Phil Dunphy

09-17-2014, 08:11 AM	#7
Ol Blue K20 Proprietor of Dale's Corner Join Date: Nov 2012 Location: Vacaville , CA Posts: 16,245	Re: 12 Bolt ID How about pics..can't be from the 80s. They were 10 bolts by then. __________________ "Some Days Chickens And Some Days Feathers" Dale XNGH ECV Sam Brannan 1004 R.I.P. 67ChevyRedneck R.I.P. Grumpy Old Man R.I.P. FleetsidePaul

09-17-2014, 08:17 AM	#8
snipescastle2 Registered User Join Date: Mar 2009 Location: WARRENSBURG,MISSOURI,64093 Posts: 1,518	Re: 12 Bolt ID could that rearend be from a '64 or '65? they look almost indentical, try looking up the axles codes for those years......I bought a 1964 12 bolt, the track bar bracket mount was welded to the the axle tube -vs. a stud in the top of the housing. Hope this helps..... Ben

09-17-2014, 09:45 AM	#10
snipescastle2 Registered User Join Date: Mar 2009 Location: WARRENSBURG,MISSOURI,64093 Posts: 1,518	Re: 12 Bolt ID I'll post a picture of mine, I removed the track bar mount, ground down the welds, powder coated it, but I'd bet that's the one you have, does it have coil spring perches on the axle tubes? Ben

09-17-2014, 10:36 AM	#11
snipescastle2 Registered User Join Date: Mar 2009 Location: WARRENSBURG,MISSOURI,64093 Posts: 1,518	Re: 12 Bolt ID Here's mine: hope this helps.... Ben Attached Images

09-21-2014, 11:41 PM	#15
crakarjax Registered User Join Date: Dec 2009 Location: Kirkland, WA Posts: 1,302	Re: 12 Bolt ID So the gears indicate 1974. Couldn't find any code as mentioned though. Still looking for the yoke application but I'll probably just measure it to figure out the proper u-joint. __________________ 1968 LWB C20 / AC / Wood Bed

10-01-2014, 09:50 PM	#17
crakarjax Registered User Join Date: Dec 2009 Location: Kirkland, WA Posts: 1,302	Re: 12 Bolt ID I measured the yokes, and while I thought that the yoke from the '74 was a 1350 yoke it looks like it is a 1330 yoke. The '71 yoke is a 1310 yoke, and seems to be in pretty good condition so I'm going to use that. The 1330 would have needed a sleeve and straps anyway so that works out I guess. The 1330 is a lot beefier at the pinion splines though, as you can see in the pictures -- and is a bit taller. Attached Images __________________ 1968 LWB C20 / AC / Wood Bed



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