I am putting a 12 bolt in my '83 Z28 because I broke the small spider gears in the posi. The rear I am using came from a '72 Monte Carlo. Looking for anybody that has adapted one of these rears in particular how you attached the torque arm to the rear. Any help would be much appreciated. Thks, Ed Hedrick

never did it, but if i were to i'd adapt the torque arm just like currie or moser does. weld a couple of bosses on the rear and bolt a adapter bracket to the bosses and bolt the torque arm to the adapter. i think you can even buy the adapters from moser or currie, maybe strange.

I did it.It was a pain in the butt but it canbe done.I bought the rear end from a yard they yanked it out of a 86 camaro so someone already did most of the fab work.They welded a block onto the rear just to the side of the case and bolted the torque arm to it.So i put it in my car and try to put on the torque arm and it hit the tranny tunnel real bad so i cut and fabbed my torque arm to fit in there but you cant changed the torque arm directing or angle to much because of the stressed that are put ont it.Mine works great but it takes some work and time to figure out exactly how it needs to sit.hope i helped.

This is a serious project. You need to make dead certain that you do not change the suspension pickup points relative to the pinion angle. If you do and the angle is off you seriously risk blowing your u-joints apart, plus the car will have a mystery vibration that you may drive yourself nuts trying to find.

I'm not trying to discourage you, or say that this can't be done by an average guy working out of his garage. I'm just trying to let you know that it isn't just a simple matter of slapping some brackets onto the new rear and tossing it in the car. There's a lot of stuff to think about.

If you decide to do it yourself spend a few bucks on an angle finder at Sears. Take readings with all the stock stuff in place. Then position the new rear under the car the same distance from the axel centerline as the stock rear sat (use jackstands and blocks of wood, or screw type stands). Then mock up the brackets and tack weld them to the housing. Check and double check the angles of the new pickup points before final welding. Focus most of the welding heat into the axel housing tubes, because they are thicker than the brackets and you will need to have good penetration to get a good weld that is strong enough to hold up to the task. If you don't feel that you can maek these kinds of welds it's best to farm the job out to a professional rather than risk your life to save a few bucks.

BTW, you can relocate your lower control arm mounting points downward a little bit for better bit off the line and at corner exit. About 1-1.5" will make a big difference. You will probably need adjustable lower control arms to make this work properly (e.g. you will need to re-establish the correct pinion angle after the new mounting points are used). These will allow for a lot more flexibility in tuning the suspension too, so they're always a good idea.

Thks for the replys, we established the pinion and axle centerlines, setup the old rear with the spring perches level, and then measured the pinion angle. Setup the 12 bolt at that pinion angle and welded the perches on with the center of the perch the correct distance from the axle and pinion centerlines. The hard part will of course be the torque arm. I did e-mail Currie, Moser, and Strange asking about an adapter. Got a quick reply from Currie saying all they had was an adapter for the Ford 9" and sent a picture of it. I have asked if I could get one. Then we would just have to figure out how to attach it to the 12 bolt. Believe this would be easier than starting from scratch. Again thks for the help to you guys and Currie. Will keep you posted on how we make out. Ed Hedrick

Good deal. Sounds like you guys know what you're doing.

The problem with the 12 bolt and the torque arm mount is that the entire centersection is cast iron and integral with the housing. You can weld steel to it for the torque arm mount, but this is never really desireable, even with the right equipment. The 9" is easy because of the steel housing. The torque arm adapter is secured to two sections of tubing welded to the housing. The aftermarket 12 bolt rears specifically designed for the 3rd gen have the torque arm mounting pad cast into the housing.

It may be simpler to make a mounting system that welds to the tubes on either side of the centersection and attach a mount pad this way. You may also have to modify the torque arm to get this to work right. Just a few ideas that may help.

I think I'm just going to buy an aftermarket "bolt in" 12 bolt rearend. I want everything to fit the first time and not have too much hassle making the disc brakes fit. I'd like to upgrade to 12" brakes at the same time. That may have to wait until 2005 income tax return because it looks like this 2004's is going to be spent on a new transmission......

Tried to attach picture of my '69 Yenko Camaro that I raced out of Jenkins Competion, but it says file is too big. Ed

i believe the center section of a 12 bolt is cast steel and easily welded with GMAW ,GTAW, or SMAW with low hydrogen electrods.

How are these guys doing the 8.8 conversion? I guess about the same way. They use a ford 8.8 center section from a mustang, then weld the thirdgen tubes on it and use the axles. Obviously the hard part is still the tourqe arm. I talked to a guy on the camaroz28.com board, and he said he spend about 1300 on his but had all good parts in it, axles, posi, gears, etc, +labor having it done. I don't know how that compares to the 12bolt and 9in prices. I don't think 1300 for a built rearend is to bad. IMO

I was concerned about the matr of the center section, but it has to be weldable as that is how GM retains the axle tubes in the center section. We put three 1" welds between each tube and the center with a TIG welder. I think all I will have to buy is the R&P and posi. In the two yrs I was racing with Jenkins, 68 & 69, with 67,68, & 69 Camaros and 68 Nova all running stock 12 bolt rears with the R&P annealed from a Rc 60 to a Rc50 the only thing that ever broke was an axle in my Yenko 69 427 one w/e that Strickler drove it at a Super Stock circuit race because I was sick. I always tried to get him to admit he was sidestepping the clutch, but he wouldn't admit to it. Based on that I am pretty sure the axles will be ok. I would have prefered to get an aftermarket 12 bolt too, but since the TremecTKO seemed to be the only trans that was rated to handle the ZZ430's 430'# of torque I bought one and that put a big dent in my mad money. I paid $100 for the rear and a friend/welder and I are doing the work. Ed

Getting a 12-bolt for $100 is a great deal. I just sold one for $650, and probably could have gotten more if I'd persued it better.

You can weld cast iron, but it's very hard to get a good weld, because of the porosity of the metal, which can trap pockets of oxygen and cause poor penetration and weld strength. Typically when welding cast iron the part is baked to remove the trapped oxygen and any oils that may have penetrated the casting. Welding is performed, and then it is heated again to relieve the stress created by welding. Using this method block and heads are now being successfully repaired, when previously they would have been considered junk.

The plug welds in the centersection are really just an afterthought for GM. The tubes are pressed into the centersection, and that's really what holds them in place. In fact the welds are usually so weak that racers and 4X4 guys perimeter weld the tubes to the centersection with a TIG to keep the tubes from rotating or ripping out under the high stress of racing and 4-wheeling.

If you have a friend that is an accomplished welder I would have him make a mount system that straddles the centersection for a torque arm mount. This will be a lot safer than trying to weld cast iron. He should also be able to make any necessary modificatiosn to the torque arm if it is required.

BTW, a T56 six-speed is rated at 450 lbs/ft and would also work well with your combination. Just FYI, the Tremec TKO is also a very stout box.

im a professional fabricator.....and thats something i wouldnt even want to do

i can think of several ways it can be done.....but it really depends what your throwing at it.....

if you plan to race this car on slicks, or make any kind of power i would have serious reservations about the strength of the mount that holds the torque arm and maintains the pinion angle.

if you plan on doing any serious racing i would buy a brand new aftermarket 12 bolt with the mount integral in the casting

if your just building a street cruiser then it shouldnt be too much of a problem

tko i beleive it's hydrogen that becomes entrapped and not oxygen. preheating to or above 350*f will keep hydrogen atoms soluable and allow them to exit and eliminate underbead cracking. the biggest concern with welding cast, especially low grade cast is carbon migration to the weld and making the weld too hard to machine and making the weld brittle. i'm no expert, only pretend to be one on here so you should do your own research before trying this at home.

its not that hard to weld cast iron......

its hard to weld cast strong, and for this particular application you need some very sturdy welding

you could look at it on the flip side.


rather then heavily modding the centersection to mount the TQ arm, you could modify or make your own TQ arm (or other link) to attach to it... not to mention, you can then make it have a adjustible pinion angle.... and set it perfect when its in the car.

You could always go with South Side Machine lift bars and eliminate the torque arm. Or fab a setup similar to theirs.

Heres some info.

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Dunno if that is in your budget or if you could fab something similar, just a thought.

ya i have that....great setup

I don't know i hate to have much headache with a project and the one you looking for is a hard one. If i were you i go with an aftermarket 12 bolt or see if south side machine still sale the lift bars for 82-92 fbody and replace the torque arm with that kit.

well i guess Easter IS the best day to resurrect a thread from 6 years ago...