How good is a 12 bolt rear?

[Dale DuBose]

I have a 1978 12 bolt rear with 4.56s and a spool. The front is a 10 bolt 4.56s and a lockright locker. How strong are these things? I know I would be better off with a 14 bolt and a d60 but this is what I have. So what are your thoughts on this being used hard off road. What can I do to make it stronger. I think the rear is a 30 spline and the front is a 28 spline, is that right?

I am new here. I come from a Jeep forum. I have all Chevy running gear in my Jeep, from motor to rearends. I get good Jeep stuff info from those guys but I'm hoping you guys will be able to help me out with all my Chevy questions.

[Mudder]

Used off road hard has the possiblity of breaking. What size tires are you running? The 12 bolt is the next best thing to a 14 bolt.

[Dale DuBose]

I have 35s now, I may move up to 37s or 38s. I say wheeled hard but what I mean is that it is a mostly an off road vehical, I drive with some sense not just right foot. I'm not going out to try to break it.

[Mudder]

I wouldn't go any bigger than a 35" tire. I have seen lots of guys do it but most magazine articles I have read, say 3/4 ton over 35's as a rule of thumb.

[diehardrider]

Originally posted by Mudder67
The 12 bolt is the next best thing to a 14 bolt.

Dont forget the dana 60

[Ratpowerd67]

the 12 bolt will be fine for now, but in the future , keep an eye out for a 14 bolt ff. there everywhere, and you can pick one up cheap. as for the d44 you will do fine, if you do alot of off road you can upgrade to stronger axles. a d60 will cost big bucks in most cases, but if you dont do any seirious offroading, you will ferform just the same........rat

[chevy68388]

dude dont worry bout what u got thell be fine i have twin 10 bolts in my chevy welded rear end and i do drive with a right foot well some time there fine never broke in the year ive had them go mudding bout every weekend but i wouldnt go over 36s if so go d60 front 14bolt rear i think i herd someone say they even make a 6 lug 14 bolt now i would like to have that

[powermad]

You can take this as ya will, this is not meant to start a pissin contest.
My buddy blew his 12 bolt posi in the sand on 33's, I blew mine out(open diff 33's) in the mud.
You have a spool in the rear which puts even more stress on the shafts, while the Jeep is not near as heavy as my K5 I would not run it stock.
Upgrade to some warn shafts and a Full floating kit and go home in one peice.
But that is gonna be real spendy.
You could swap in a 14 Bolt FF but the ground clearance ya would lose would not be worth it.
With 33's and a FF I have 8.5" of clearance under the housing.
If I shave it I will gain another 3/4".
With the rear welded up I can usualy go anywhere I want as long as the diff dosen't high center me, which is all the time.
But I have an 8" lift in the garage and 42's are planned, but that's neither here nor there. LOL
One thing to consider with the 12 bolt is if a shaft lets go you have to get real creative to get out unless you carry spare shafts.
If you convert to a disk rear at least the wheel will not walk out of the housing if the shaft breaks.
If hard wheelin is in the works those are some things to consider.

[Dale DuBose]

Were can I get a full floater kit and axles for it. Whould that make it strong enough? If I get a 14 bolt now I will have to buy another set of gears and a locker. And I still would have the 8 lug thing to deal with. I heard that the 6 lug 14 bolts arn't good either.

[Dale DuBose]

Maby for the price of the ff kit and axles I can get gears and spool for the 14 bolt. I'm sure I can get the 14 bolt cheap. But what about the lug patterns, How do I make the front and back match?

[Ratpowerd67]

you will have to covert your d44 to 8 lug by changing out the spindle assembly.

[powermad]

Anywhere that sells Warn products can get the FF kit.
4WPW has them for $900.
That's the moly axles, hubs and bearings and your choice of lock outs.
Either the full time one or selectable like the front.
The first time I seen a set on a rear axle I was thrown for a loop.
Add is some Warn hub fuses and that is about as dependable as ya can get unless you get realy wild and get custom front and rear Dana 60's

Here are the Warn axles
I believe the hub fuse is about $15, that's a bunch cheaper than a blown ring and pinion.

[Fast68Chevy]

the problem with truck 12 bolt axles is that the pinion stem diameter is very tiny and the pinion nuts have problem of coming loose and then there goes your gears and bearings.
the 8.5" 10 bolts are technically more reliable and stronger in all actuality, the dana 60 are not stronger than a 14 bolt full floater, but the dana 60 do give you more ground clearance,.

14 bolt youll never break and it takes well over 200,000 miles to wear oen out to make it need rebuild, i learned this from colorado k5 guys,.
14 bolt full float is the ultimate strength axle and is under all 73-80 3/4 and 1 ton trucks if doesnt have a 60 rear. 4.10(typically SBC trucks) and 3.73(typically BBC trucks) are most commmon 14 bolt ratios youll find around and alot of them have locking units in them.

81 and later trucks saw large use of the not as big and strong 9.5" semi floater 14 bolts and some of them were 6 lug and some were 8 lug. alot of 90's 4x45 and 3/4 tons have the 9/5 semi floater in them, the 9.5" used crappy gov lok units that are definitely nothing to brag about having.

12 bolt units changed to gov lok in about 75 or 76 from the eaton clutch units(very bad change)

your front axle can be converted to 8 lug with 3/4 ton spindles easily,.

good luck

[palallin]

The 12-bolt in my truck has well over 300,000 miles on it and is as tight as can be. This truck has seen a hard life--it was a fireman's truck for much of it's life. I had a diff carrier bearing go out in another 12-bolt once, but that's the only failure of a 12-bolt in a very long family history of them.