Rebuild or Replace?
 

My GM 12 bolt rear whines and moans. Sadly, my rear makes more noise than my exhaust now. I have popped off the cover for a visual examination, and the wear pattern is terrible, chips in the ring itself... This death trap is going to lock up someday so I need to have it rebuilt w/ new ring and pinion, or replace it with a junkyard find.

Rebuild or Replace? Factor in cost, effort, etc... Thank you in advance.

Re: Rebuild or Replace?
 

i had mine rebuilt
somebody weilded stuff that they shouldn't
i felt it was better to rebuild as other stuff would prob break replaceing
used offset axle bearings when going back together,(new spot to roll on)

Re: Rebuild or Replace?
 

Why not just check out a used one. It seems to me that you could take the cover off and have a good look see on a used one. On the 3 squares I have owned I have never had any trouble with the rear axles, but they were all 3/4 ton trucks. I did overload them all on many occasions. In your neck of the woods old squares should be all over the place. Maybe you could score a whole truck with a good rear axle and sell/scrap the rest of the truck.

Re: Rebuild or Replace?
 

I had a spare 12 bolt n had it rebuilt.New gears, (3:73) a auburn posi, richmond rebuild kit.Also added disc brakes to it.It all depends on what your budget is.Do you want to rebuild it n feel safe or take a chance and grenading a rearend? Id go for the rebuild n feel more safe.

thanks
pat

Re: Rebuild or Replace?
 

Cheapest thing will be get another completes axle (minus brakes) from the junkyard. Done it many times and never had a problem. just check inside the pumpkin before you buy it or get a warranty. Then put new wheel bearings in it and all seals except the pinion as long as it doesnt leak terribly and call it a day.

On a side note; the axles from a VAN will NOT work, they have to be from a squarebody for the spring perches to be in the right spot.

Re: Rebuild or Replace?
 

What'd you spend on your rebuild? Sounds terribly expensive... What can I look forward to spending for a straight forward rebuild? No Posi unit, just a rebuild and new ring and pinion install, and I'll be keeping the 3.08 ratio.

Re: Rebuild or Replace?
 

Welll the thing is i went a lil overboard on the whole build itself since i wanted everything clean n powdercoated.You can rebuild it for probably around 3-400 depending on where you shop.But while your rebuilding it, and want a lil more pep you could upgrade the gears to like a 3.42 but dont go overthat cause youll be increasing the rpms more if you go to like a 3.50.If you are using it on the highway then the 3.08s are good.Im sure you will have them look at the ring n pinon for chipped teeth.

thanks
pat

Re: Rebuild or Replace?
 

Let me ckeck my parts truck . Its a 77 with a 12 bolt . I do not know what gear is inside but if it is a 3.08 gear , I will let you know .If it is nice and the right gear I would sell it .PM me in a day or two so I do not forget .
Frank

Re: Rebuild or Replace?
 

Thank you in advance for going through the trouble. There may be other parts I need that you may have. I'll include it in the PM... :metal:

Re: Rebuild or Replace?
 

$1200. to rebuild but it sure needed it
3.73 rear end
new brakes,e-cables,shoes,wheel cyclinders,.....and all the rest of the bits
now after about 5 years ....had no issues.....good insurance ....no regrets......
beats walkin or drivin a ford lol

Re: Rebuild or Replace?
 

Just bringing this to the top again because I can't get a real estimate out of shops. I have a GM 12 bolt w/ 3.08 open rear. I want to rebuild it and keep the ratio the same. I will purchase a ring/pinion and complete rebuild kit and take it to a shop. What can I expect to pay in labor for a rear end rebuild? I will have approximately $300 or less invested in parts.

Re: Rebuild or Replace?
 

I had a 3.08 open diff in a 76 with a t350 on it. In canada, they wanted 1700 to make it a 3.73 and change all the bearings and races and add an eaton posi.
In austin I'm thinking you'd pay about 1400.
I got a 3.42 from a suburban and the only thing I had to change was the back rear cross-u joint to make it match the 10 bolt dif yoke.
FYI.

Re: Rebuild or Replace?
 

Alldata shows about 6hrs labor to overhaul rear diff. where I work that translates to aprox $600. I would recommend buying parts through the same shop that does the work, that way they can warranty the whole job(not just the "workmanship") because every shop is going to tell you the parts you supplied broke and they installed them correctly. with that being said it is hard to quote a job over the phone, pick a shop with a good rep and take it there, let them look at it and give you a real quote, and make the stick to it. Beware of the shop that says they can do it for way cheap though! it always cost the same or more in the end. my guess would be $1000 to $1100.

also, might concider the used rear end road...have had pretty good luck with "recycled parts" at the shop i work at, would save a bunch in labor

Re: Rebuild or Replace?
 

i agree about the shop having issues with BYOP....and yes i wouldn't doubt a shop would argue about what somebody brought with them....
and mine took 1 guy (not CTC)two days pretty much.....and with me watching/asking questions
after Canadian Tire ran my 83 camaro into the lift, my truck or car dosn't go in a shop without me.....watching (that learning alone is worth $$)

Re: Rebuild or Replace?
 

Im about to have my rear end rebuilt in my '90 model K5. I took it to a very good shop here locally and they quoted me $350-$400 labor with me supplying my own parts. I thought this was pretty good. I currently have 3.73's in the blazer and Im switching to 4.56's since I will be lifting it and running 35" tires. The new ring/pinion set from Summit is $150 a set......dont knock Summits parts unless you have had a actual bad experiance with them, keep the "hear say" and rumors at the water cooler. Also, a complete rebuild kit is about $100 through Summit. Im changing out gears in the front and rear so it will be a little more, but just the rear end rebuild was $350-$400 labor.

Re: Rebuild or Replace?
 

That $1000-$1200 price tag is pretty cosistent in Austin, TX. It seems like most shops try to talk you out of doing a rebuild. I have a sneaking suspicion that overhauling a rear end is not a glamorous process, thus promotes lazyness in mechanics city-wide.

That being said, I have also checked into local junkyards. One junkyard has an '80 silverado 1/2 ton w/ a GM 12 bolt (3.08). Condition unknown, and I couldn't inspect it because they were closing when I arrived. I would like to return to the yard prepared...

1. How to I determine if a rear is good or bad?
2. Does anyone have a picture or video link that could assist me?
3. What can I expect to pay for a used GM 12 bolt rear?

Thank you in advance. Have a great day.

Re: Rebuild or Replace?
 

getting my rearend done now and they quote me 600.00 to do it but i have to bring all the parts. that with a 3.73 gear , powertrax posi locker,new brakes, diff cover plus other things

Re: Rebuild or Replace?
 

Call Larry Green. he lives in Cameron (I think) TX. 254-482-009nine.
I know he owns about a million 67-72 trucks and I think he has 73-87s as well.
I just bought a great used 12 bolt rearend for 150 bucks but that was probably a rare deal. I see them on Craigslist for 300+.

Re: Rebuild or Replace?
 

Rebuilding is going to cost, plain and simple. The gears, bearings, seals, etc are going to be at least $250 and you are looking at a labor cost of at least that (probably more depending upon your particular part of the country)....So yo are looking at an absolute minimum of 5 bills.

From a strictly cost effective way to look at it, that is an expensive way to keep the same ratio and not add a traction device. If you are looking to do either of these up-grades, it becomes a different story..

Personally, I would recommend looking for a used rearend. It may take a little work on your part, but it will come out a lot cheaper. Inspecting the axle is not that hard, but you do need to do it to be sure of what you are getting.
You want to be sure to pull the cover off and see inside. This will assure you of the gear ratio in the first place, but more importantly you can see the actual contact area of the gears.
The main thing to look at, other than the obvious wear (metal shavings, etc.) is the backlash. That is the "clearance" between the ring and pinion themselves. Hold the pinion so that it cannot move and rotate the ring gear back and forth. It should move only slightly before it "hits" the pinion and stops. We are talking only a few thousands of an inch here, nothing crazy. If there is a lot of movement, it is excessively worn.....and there is no "fix". It is no better than the one you already have.

While doing this you may come across an axle with a "Gov-Lock". It's a factory positraction unit. In a light duty application, they are OK, so it's not necessarily a "deal breaker".....but don't pay any extra for it.

Even if the used axle does fail on you after a few years, it was cheap in comparison. Sure there is some work involved, but you can save quite a bit of money for your efforts.

As always, synthetic lube is your friend here. Cheap insurance.

Re: Rebuild or Replace?
 

Call A-Ok Chevy Parts in Elroy. Elroy is a few miles outside of town. I bought a 12 bolt from years ago. Ron specializes in square body parts.
(512) 247-4268
140 McDowell Rd Unit B
Del Valle, TX 78617

If you need parts or info in Austin, give me a buzz.

Re: Rebuild or Replace?
 

I took a 12 bolt from another truck and took it to a shop with a new complete kit minus the brakes and had it done for $75. This was going from 3.07 to 3.73 (yes I said 3.07 it shows this on the sticker).

Re: Rebuild or Replace?
 

Sorry for not getting back to you on my rear . It looked pretty bad inside . I looked at a 48,000 mile original 6 cylinder 80 model with a 12 bolt rear that the that the guy wants $250 for but it had a 2.76 open rear . I know you wanted to stay at 3.08. I have one other truck to look at . PM me this saturday and I will let you know what it has in it .
Frank

Re: Rebuild or Replace?
 

Correct me if I'm wrong, but I thought that 3.08 was the highest ratio one could get for a GM Truck 12 bolt? It's the highest that jegs or summit carries. 2.76 can be offered in 10 bolt rears, but not 12. Am I completely wrong on this. I wouldn't mind a 2.76 rear, I just didn't think that was possible. Give me more information on that guy's rear, but I'm fairly sure it would be a 10 bolt.

I'll PM you just to keep in touch should a rear end come about.

Re: Rebuild or Replace?
 

Where was this done? That sounds too good to be true. You scored huge on that deal. BTW, I love your truck. I was looking for a SWB Bonanza Big 10 for a while, but settled on a SWB Bonanza. That's got to be one of the rarest combinations on the planet. Dig it.:metal:

Re: Rebuild or Replace?
 

I am pretty sure it was a 12 bolt . I looked at the rear myself and the overall truck . It has 48k miles and I am sure they were original . I will see if he still has it and get back to you.
Frank