How To - 3/4 Ton - Converting to a 14bolt

[LostMy65]

CaptainFab has been making these for the larger diameter axles such as the 14-Bolt used in Gm 3/4+ Ton Trucks from 1973 to 1987?
Captain will know more specifics.
Either way, I have been asked by several members how I went about converting my 66 3/4 to a 14-Bolt.

CaptainFab's Perches/Seats/Saddles


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I layout much of the 'How To' in my 66 Build Thread, but I figured I'd make a dedicated thread where others could ask questions and share experiences.

So, I'll layout how I did mine.

14-Bolt Ready to grind off Leaf Spring Perch's:

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Leaf Perch's and Shock Mounts ground off:


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Here is CaptainFab's Trailing Arm Perch - Fits Perfect:

[LostMy65]

I don't want to be doing this from under the truck, so I set-up kind of a jig to line everything on the Eaton up.
I nailed 2x6's to my shop floor so they won't budge.
You could nail yours to a piece of Plywood.
I traced the Eaton's Trailing arm perches U-Bolt holes.
Then I will use this for getting CaptainFab's new Perches lined up on Corp 14-Bolt to match the Eaton perch location.

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[LostMy65]

I scribed and cut a piece of scrap particle board at the angle that I will need for setting the 14-Bolt at the same angle as the Eaton.

[LostMy65]

I got Captainfab's Perches tacked.

Pinion angle is set the same as it was on the Eaton.

[LostMy65]

I got the u-bolts made and bolted them up the 14-bolt to the trailing arms.



For the panhard bar, I cut the bracket off the Eaton and welded it to the 14-bolt.

[LostMy65]

[Captainfab]

Thank you for starting this thread Robert

I'm sure this will help those that are considering converting to the 14 bolt for the advantages of better gearing and better parts availibility.

One question. Did you have to shorten the driveshaft, and/or did you need a different rear U-joint?

[LostMy65]

I did not need to shorten the driveshaft.
I did not need a different U-Joint.
I bought new U-Joints, but they were the same size as I had with the eaton.

[gmcdeadhead]

i'm gonna order a set of perches from captain fab and do my conversion over the winter . does anybody no where i can get some drum brake backing plates from for the 14 bolt?

[cp_66_c20]

Is the dually Dana 80 a good reared to use for a conversion? I was looking at it for the gross weight it can handle. I know that it will take some fab work witch i understand. If not then i will go for the 14 bolt Dana 70. Witch brings me to another question. Can you weld on the 60 to 66 frame? I was told and heard that it was heat treated and that it would make the frame weaker. Thanks for any info and the write up answered some questions i have had.

[Captainfab]

What is the diameter of the drums on yours. There are 2 different sizes of drume, and hence the backing plates. What is wrong with yours?

Originally Posted by gmcdeadhead

i'm gonna order a set of perches from captain fab and do my conversion over the winter . does anybody no where i can get some drum brake backing plates from for the 14 bolt?

IMO, unless you are building a C30 for doing some serious hauling, the Dana 80 is a bit overkill. The 14 bolt, or a Dana 60 or 70 would be fine for a C20. To my knowledge the frames are not heat treated. Although they are typically an alloy of steel that is tougher than mild steel and will flex more without fatigue. You just need to be an experienced welder to correctly weld on a frame. Otherwise you could have a catastrophic failure.

Originally Posted by cp_66_c20

Is the dually Dana 80 a good reared to use for a conversion? I was looking at it for the gross weight it can handle. I know that it will take some fab work witch i understand. If not then i will go for the 14 bolt Dana 70. Witch brings me to another question. Can you weld on the 60 to 66 frame? I was told and heard that it was heat treated and that it would make the frame weaker. Thanks for any info and the write up answered some questions i have had.

[cp_66_c20]

Yea that's what i was wanting to build it for. I plan on hauling cars, trucks, maybe a tractor or two, and some other things. I have some experience welding but i am not and expert yet. The reason i was asking is cause i don't want to put the time and money into it. Then accidentally bend frame from a week spot or something more catastrophic like you were saying. Thanks for the wealth of knowledge and the help.

[gmcdeadhead]

lost my 65, that receipt you have showing the u bolts that were made up , is that the right size and dimensions i should go get made up to do my 14 bolt conversion? thanks

[pope]

Made the same swap in my 4x4, sure is nice to have some taller gears!

[jtrichard]

what did you have to do with the u-bolt spacing on the trailing arms?

[gmcdeadhead]

i did the 14 bolt conversion on my 1966 c-20 already. i got a whole chassis from a 1987 1 ton chevy truck and used the 14 bolt for the conversion.(i will be doing the front end conversion also from the chassis i bought), i had to get my drive shaft cut by
1-1/2 inch, i have a 292 with 4-speed in it. i bought standard u-joints and bought a new carrier bearing. the rear brake cable on the left side i had to modify to get it to work , the right side worked ok. the dimensions for the u-bolts work out great , went into the trailing arms with no problem. capt fabs perches worked very well also, any other questions feel free to ask.

[jtrichard]

was the 1 ton a C&C? drw? i found a C&C that i sold 8 years ago now getting it back for $100 it is the same width +/- 1/2" as the eaton i have a 82 donor truck with 6.2 diesel and good front suspension and good rear 14 but i did not fight the 3to4" wider ....i have not checked the yolk to center on both axles but you said you had to shorten the shaft and lost 65 said he did not???

[LostMy65]

I had enough depth still available in my slip yoke that I didn't need to shorten my shaft.
gmcdeadhead may have needed to shorten his so his slip yoke wouldn't bottom out.
Posted via Mobile Device

[gmcdeadhead]

yep , i had to shorten so slip yoke would not bottom out.

[LostMy65]

For some reason I didn't remember I made this thread. Someone was asking about it.

[Woogeroo]

This thread was added to the Driveline category of the Engine & Drivetrain section of your 60-66 FAQ Index.

Thanks for sharing.

-W

NOTE : if this link changes in the future, look for the sticky at the top of the 1960-66 Message Board.

[earl84]

This thread helped me immensely when I put a 14 bolt in my C20. Thanks for doing it, and thanks Woogeroo for your FAQ work.

[LostMy65]

Originally Posted by earl84

This thread helped me immensely when I put a 14 bolt in my C20. Thanks for doing it, and thanks Woogeroo for your FAQ work.

Glad it helped. Thanks.

Here is the other thread by azdeltawye that I think was inspired by mine:

http://67-72chevytrucks.com/vboard/s...d.php?t=624445

[azdeltawye]

Originally Posted by LostMy65

…
Here is the other thread by azdeltawye that I think was inspired by mine:
…

Yes, I was inspired by your thread.

I forgot to give credit where credit was due.

Thanks!

[LostMy65]

I had no trouble getting the new U-Bolts through the holes in the Trailing Arms.