14 bolt 6 lug from 90s Chevy...

[Jl8806]

I just bought a 68 c10 swb with coil springs, I know the leaf spring mounts and shock mounts will have to be cut off the 14 bolt but is there anything else that would keep me from swapping this in the 68? Width the same? I'm about to have the frame and rear end sand blasted and painted so I want to go ahead and have the rear diff that I'm going to use in there. I'm going to with a 6.0 4l80e and I'm hoping for 5-600 hp eventually... Are there kits out there with the mounts I need for the 68? I'm new to all this, would I be better off trying to find a 12 bolt? Thanks

[Jl8806]

Also what did the 12 bolts come in so I will know what to look for

[Ironangel]

Get in touch with "CaptainFab" for details and the beefiest trialing arm mounts available anywhere. My BBC twisted the factory perches nearly off the axle, replaced them with a set of his perches and they're still holding strong after 3 years of 500HP hole shots on slicks...The GM "10.5" 14-bolt axle is practically bullet proof, WAY tougher than the Dana 60...Here's some good info on the 14 bolts, https://www.pirate4x4.com/tech/billavista/14b_bible/ The GM "Truck 12-bolt" made it's debut in 64 and was the standard C/10 axle until like 81. Cant be mistaken as it has 12-5/16" x 3/4" (1/2" Hex) bolts in the cover, the 14 bolt has 14- 3/8"x 1" bolts in the cover...CaptainFab hangs out in the "Engine & Drivetrain" section...

[Mike C]

The 12 bolt is rated to 3500# GVWR and the semi-float 14 is 5500# GVWR and if you compare the two side by side, you will see why. I think the SF 14 is an underrated swap item and the cheapest/easiest way to get some beef in place of a 12 bolt.

The axle tube is 3 1/8” so you will have to re-profile any perch kit you get slightly to fit against the tube since they are made for 3” housings. If it has a GovLok in it, my opinion is you should replace it with something else. Either the Eaton posi or the Detroit TruTrac would be my choice. And obviously add one of those if it is an open diff.

Obviously you want to find one with the gear ratio you prefer to save on having to buy and have setup a new ring and pinion.

I swapped a SF14 from an 86 Suburban into my Jimmy with 4.10 gears and the GovLok and another with 3.73 gears from an 84 Sub into my kids Jimmy project.

[Jl8806]

Originally Posted by Ironangel

Get in touch with "CaptainFab" for details and the beefiest trialing arm mounts available anywhere. My BBC twisted the factory perches nearly off the axle, replaced them with a set of his perches and they're still holding strong after 3 years of 500HP hole shots on slicks...The GM "10.5" 14-bolt axle is practically bullet proof, WAY tougher than the Dana 60...Here's some good info on the 14 bolts, https://www.pirate4x4.com/tech/billavista/14b_bible/ The GM "Truck 12-bolt" made it's debut in 64 and was the standard C/10 axle until like 81. Cant be mistaken as it has 12-5/16" x 3/4" (1/2" Hex) bolts in the cover, the 14 bolt has 14- 3/8"x 1" bolts in the cover...CaptainFab hangs out in the "Engine & Drivetrain" section...

Are you running a 12 or 14 bolt

[Ironangel]

I'm running a 12-bolt...With welded tubes and a Moser girdle. If it ever breaks I'll replace it with a 14-bolt...4:56 gears with an Eaton Posi. I rebuild axles for my 4x4 and drag racing friends. The GM Truck 12-bolt is a pretty tough axle and will withstand a beating, but don't compare to a 14-bolt. The 14-bolt is a "Full Floating" axle set up which in my case if I ever go that route will require axle specific wheels for the rear because my 72 C/10's have 5 lug axles and wheels...

[Jl8806]

I haven't even looked but should my 68 swb have a 12 bolt? I'm at work right now and just trying to get everything planned out, I've found a 14 bolt 6 lug at the junkyard that I was going to go pick up this afternoon, it's only 500 but I still don't know what to do... I'm afraid I'll get in a mess trying to get the spring perches and shock mounts right

[Ironangel]

If your just starting out I'd take a hard look at the 12-bolt. I'd only recommend the 14-bolt to the hard core high HP drag racer or off road applications. Your 68 would have a 12-bolt unless a previous owner stuck a 10-bolt under there. I'd pass on that 14-bolt if I were you and find a 12-bolt or rebuild the one you have. I have a good 12-bolt open diff (non-posi) with perches for trailing arms I'd let go for $200 w/5 lug axles. The 80's 12-bolts have 6-lug axles or a guy can buy 6 lug aftermarket axles. Another thing to consider too is that some 70 and all 71 and up 12-bolts are 1-1/2" wider than the 67 - 69 axles...

[weim55]

Using a 14 bolt semi floating axle with a six bolt wheel flange is a really good idea. Super strong and not too difficult to locate. Should have a larger rear drum brakes as well. The problem I think you will run into is the axle Width. The 88-98 trucks those come in use a seriously negative offset wheel. Might be too wide under a 67-72. Maybe someone on the 88-98 section here on the board can measure one for you(??)

Steve weim55 Colorado

[weim55]

Also: I’ve never seen a 2 Wheel Dr. version of the 14 bolt do you wish to use. If they do exist there might be a difference in the width between a 2 Wheel Dr. and four-wheel-drive version.

Steve weim55 Colorado

[mkmc69]

I have one from a 98, I believe. It is a posi, and has 3.42 gears. I thought they were too wide to swap to our trucks.

[Jl8806]

I'll do some measuring when I get back to the shop, my 97 half ton just has a 10 bolt but they should be the same width. The back wheels on the 88-98 trucks are narrower than the front, I would think it would work but maybe not...

[Jl8806]

From what reading I've did apparently there is a 2wd 14 bolt and it's narrower than the 4wd, so that's probably what I would need but I'd say it will be hard to find

[Rooster73]

Yeah your right, measure carefully, 14 bolt semi came in 2 different widths, awesome brakes(bigger) but a major power sucker.

[Mike C]

Some big block 68 GMC trucks came with a 6 lug Dana 60. THey are out there but pretty uncommon. Chevrolets...maybe?

The 6 lug was available in the light duty 2500 truck staring in 89 or so? It was the heavy duty option in the Z71 4x4 1/2 ton trucks. I’ve never researched width as it worked fine in my application.

It’s not a hard swap, but would really help if you had a capable mentor close by. You will most likely need conversion u-joint (1310-1330) and change the lug studs on one end of the other so they match. The later axle will have 14mm studs vs. the 1/2” on pre ‘71 truck.

[57taskforce]

Originally Posted by Mike C

Some big block 68 GMC trucks came with a 6 lug Dana 60. THey are out there but pretty uncommon. Chevrolets...maybe?

The 6 lug was available in the light duty 2500 truck staring in 89 or so? It was the heavy duty option in the Z71 4x4 1/2 ton trucks. I’ve never researched width as it worked fine in my application.

It’s not a hard swap, but would really help if you had a capable mentor close by. You will most likely need conversion u-joint (1310-1330) and change the lug studs on one end of the other so they match. The later axle will have 14mm studs vs. the 1/2” on pre ‘71 truck.

They also came in the 7200 lb 3/4 ton trucks as well.(not a very common gvw, most 3/4s were the 8600 that got the 14ff) My brother had a 6 lug ‘90 3/4 ton truck a few years back.

[special-K]

They were light duty 3/4t rears... hence 6-lug semi-floating vs the traditional 8-lug full-floating normally found in 3/4t trucks. I think the negative offset wheels and trimmed fat body style work together here with the track width remaining about the same as pre-IFS trucks. The front sheet metal tapers in from the cowl and the bed tapers in to the rear. Also the body rolls under a good bit.

Has anyone drilled these flanges for 5 on 5? Is the center bore an issue? Is the center bore an issue for earlier wheels? I know I've seen 88-98 K1500s with 8" rallyes before

[Jl8806]

Anyone know what the narrow 14 bolt came in? I'm going to start hunting for one

[Rooster73]

k2500 was wider than c2500

[Jl8806]

Ok I've found a 14 bolt that will work, now I just need to know what will I do about trailing arms since the 12 bolt is a 3" tube and the 14 is 3 1/2, I can get the u bolts but the holes on the trailing arms aren't going to line up

[TIMCHNE]

Originally Posted by Jl8806

Ok I've found a 14 bolt that will work, now I just need to know what will I do about trailing arms since the 12 bolt is a 3" tube and the 14 is 3 1/2, I can get the u bolts but the holes on the trailing arms aren't going to line up

There is enough room for the bigger tubes between the holes in the trailing arms. I put one of these in my daughter's 68,it looks perfect under the truck. You will need to find a way to put a panhard bar on it. I took one off 3/4t eaton coil rear, you need the bar housing bracket and frame brackets. I had one in my 72 SWB 4x4 that was out of a mid 90s so it was about 4 in wider than stock puts the rear tires in line with the fronts. IMO the perfect rearend for any 1/2 ton, Chevy used a version of the 9.5 14 bolt in the SS454 trucks same as they used Dana 60s in big block 4spd trucks till 1970.

[Jl8806]

This should take care of the panhard bar, that way the only work I should have to do on the 14 bolt is shock mounts and saddle brackets

http://www.classicperform.com/Store/...k/6072DRCK.htm

[Jl8806]

Originally Posted by TIMCHNE

There is enough room for the bigger tubes between the holes in the trailing arms. I put one of these in my daughter's 68,it looks perfect under the truck. You will need to find a way to put a panhard bar on it. I took one off 3/4t eaton coil rear, you need the bar housing bracket and frame brackets. I had one in my 72 SWB 4x4 that was out of a mid 90s so it was about 4 in wider than stock puts the rear tires in line with the fronts. IMO the perfect rearend for any 1/2 ton, Chevy used a version of the 9.5 14 bolt in the SS454 trucks same as they used Dana 60s in big block 4spd trucks till 1970.

Were you using stock trailing arms?

[TIMCHNE]

Originally Posted by Jl8806

Were you using stock trailing arms?

Yes stock control arms it's pretty tight.

[GMC71k20]

Originally Posted by Jl8806

Ok I've found a 14 bolt that will work, now I just need to know what will I do about trailing arms since the 12 bolt is a 3" tube and the 14 is 3 1/2, I can get the u bolts but the holes on the trailing arms aren't going to line up

What year/model axle did you end up using?

How did the perches work out?

Thanks in advance