found this one my 12 bolt rear end what does it mean

[Mrbret]

I would love if you guys could help me figure out what kind of rear end i have and the gearing..

[b454rat]

Those numbers don't mean squat. Hard to tell, but sorta looks like a 10 bolt. can't tell gears from those numbers either. pull cover and look numbers on edge of gears, 41-10 or something like that.

[Mrbret]

It’s not a 10 bolt because the post clearly states it’s a 12 bolt. After doing some research with the numbers and looking at other forms I found that it’s a 70’s rear end and is geared at 3.07 since the truck has a 292 with a th350 and np205. 3.07 is the stock gearing. My dad says the truck is slow so this would make sense. But my real question is what frame is actually on the truck. My dad clams it’s a k5 chassis but to me it looks like a k10 because the frame hasn’t been lengthen to fit the 3100 body.

[Keith Seymore]

Originally Posted by Mrbret

It’s not a 10 bolt because the post clearly states it’s a 12 bolt. After doing some research with the numbers and looking at other forms I found that it’s a 70’s rear end and is geared at 3.07 since the truck has a 292 with a th350 and np205. 3.07 is the stock gearing. My dad says the truck is slow so this would make sense. But my real question is what frame is actually on the truck. My dad clams it’s a k5 chassis but to me it looks like a k10 because the frame hasn’t been lengthen to fit the 3100 body.

...

[Keith Seymore]

It might be time to slow down and back up a bit -

a) If you want to know about the frame then why are you posting zoomed in pictures of the rear axle?

a - 1) If it is to use the axle to help identify the frame: How do you know the axle is original to the frame?
a-2) What numbers did you use to decide it's a 3.07 axle (not the casting numbers shown, for sure).
a-3) If it does check out as a 3.07: how do you know that's what is still in there? A lot of gear sets get changed in forty or fifty years

b) What kind of vehicle are we talking? A body swap?

c) K-5, like a Blazer? Is there a VIN stamped somewhere on the frame?

d) Perhaps some pictures of the frame, and the vehicle, would help.

K

[jeffahart]

Originally Posted by Keith Seymore

...

I got a good chuckle from that image.

[Mrbret]

Originally Posted by Keith Seymore

It might be time to slow down and back up a bit -

a) If you want to know about the frame then why are you posting zoomed in pictures of the rear axle?

a - 1) If it is to use the axle to help identify the frame: How do you know the axle is original to the frame?
a-2) What numbers did you use to decide it's a 3.07 axle (not the casting numbers shown, for sure).
a-3) If it does check out as a 3.07: how do you know that's what is still in there? A lot of gear sets get changed in forty or fifty years

b) What kind of vehicle are we talking? A body swap?

c) K-5, like a Blazer? Is there a VIN stamped somewhere on the frame?

d) Perhaps some pictures of the frame, and the vehicle, would help.

K

Hello Keith,

I read you thread earlier today it was impressive. Lets start this from the beginning, my dad has owned the truck since he was a jr. in Highschool so since the late 70's. He purchased the truck already complete.... The guy that sold it to him claimed it was a k5 chassis setting on the 3100 body. Last week my dad said he even got a K5 emblem with it he just never put it on. The last time the truck was driven was 1995 because that is what the registration said inside the glove compartment. My dad gave me the truck 14 years ago and it just sat. My wife and I purchased a house about a year ago. According to my wife as long as I do all my projects i can bring the truck over and start working on. Finished all the b.s. she wanted me to do. I cleared the garage so i can put the truck in it and start working on it. That was about two months ago... My father-in-law and I got the motor turned over last month. She fired up perfectly fine, that 292 is a good sounding motor. We decided it was smart to start with a new wire harness since all the wires in the truck were a mess. I got the harness in last week and i was cleaning all the webs off and run into the axle and took the photo of it. I was looking over the frame from under the truck and it isn't cut or welded so I have no clue what frame is on the body. I have tried looking for the vin numbers on the frame but no luck. i have all the vin stuff for the 3100. Here and the photos.

[Mrbret]

more photo

[Mrbret]

more photos

[b454rat]

its' a 12 bolt rear, but don't think it's on a K5 frame, wheelbase looks to way too long for a short wheel base of a K5....And WTF kinda of t-case is that?

[B. W.]

Looks like a NP 203 tcase

[nonstop]

May be mistaken, but that looks like the factory frame. Spring hangers and parking brake cross member linkage looks like an AD original set up. It also has a pretty thick leaf pack in front.

[Mrbret]

here is the numbers off of the transfer case

[b454rat]

Must be an early 203, all ones I’ve seen had aluminum tail housing. I was gonna say something bout frame, but thought it was a 67-72 style and I don’t know much bout those.

[Mrbret]

Here is the front of it

[kwmech]

1973-74 NP203 t-case...first design had the cast iron 1 piece tail housing. Looks like the original frame the way the spring hangers look. Get us a couple of shots of the front frame horns and steering box area

[Keith Seymore]

Originally Posted by Mrbret

Hello Keith,

I read you thread earlier today it was impressive.

Thank you; the photos definitely help.

It's not something I recognize so I will defer to what the others might think.

K

[dieseldude4bt]

That is not a Blazer frame.
It looks to be the original frame with 4x4 running gear added.
A Blazer frame would not need the spacer blocks at the transfercase crossmember and the front rear spring hangers are wrong for a blazer.
What does it have for steering box mount? Could you show a picture of that?

[70K10Hunter]

you need to post some pics of the cab and bed mounts. looks to be a 12 bolt in the rear and a corporate 10 bolt up front with full time hubs and yes that is an early NP203, If I were to guess the running gear is early/mid 70s. The spring hangers got me puzzled tho, they are under the frame and not mounted beside the frame. Maybe the frame is from the 3100 and the running gear is from a K5??? Another thing or 2 I noticed is the rather large webs/gussets mid frame under the back of the cab.... Also look at the cab step mounts they are secured directly to the frame........I think its the original frame.

[b454rat]

Not a 10 bolt but Dana 44. Same difference tho.....what others said, looks to be original frame/converted to 4wd, prolly using running gear from a k/5, which is the same as a truck

[Mrbret]

Originally Posted by b454rat

Not a 10 bolt but Dana 44. Same difference tho.....what others said, looks to be original frame/converted to 4wd, prolly using running gear from a k/5, which is the same as a truck

Yes you are correct it’s a Dana 44 I found the stamp. After looking further into the frame it is the 3100 frame modified to fit all the k5 running gear. From power steering to front disk brakes.

[b454rat]

Pretty cool truck/build!!!!!