So give me the reasons why it is a bad idea to try to go through with this procedure.

I already know of a very compitent place that is capable of welding all of the necessary brackets to the axel, so all i need to do is find one out of the older t/a's or whatever. Is there any reason this cant be done?

I am looking into this because my 10 bolt isnt holding up too well with the minor mods i have now and i have a manual tranny as well as more engine mods in my future so im definitly gonna be blowing up that 10 bolt. And i am not in a position where i am going to be able to afford a 9" any time soon

 

I do not believe that it is a bad idea if you are going to do it yourself, or can get it done for cheap.

The cost from the website I posted is like $1500.00 to $1600.00. For a few hundred more you can get a 12 bolt or 9 inch.

So to buy one IMO is not worth it.

http://www.amazingmechanical.com/rearend.htm

I am also planning on doing this. I have a rear off of a 96 Impala SS with a 3 series posi and disc brakes that I am going to modify. I want to buy new brackets and spring perches but I can't find anywhere to get them. Looks like I will have to make them or rob them from a used rear.

From the pic on the web site it doesn't look like that big a deal to make them.

The place you have doing the work, do they have a line on getting new brackets and perches?

 

From a strength standpoint the 8.5" 10-bolt is a decent rear. A 12-bolt's ring gear is only 8.625", so the difference in strength is negligible.

From a fabrication standpoint you're looking at some work. You will have to fabricate the torque arm mount, since it won't exisit on an 8.5" 10-bolt, so this will need to be built in the same manner as an aftermarket 9". The aftermarket 12-bolts have this mount cast integrally with the housing, which simplified thier installation. For the spring perches, LCA mounts, and panhard mounts you are better off cutting them off a 7.5" 10-bolt rear and welding them to the 10.5" 10-bolt. These could be fabricated, but it would be time consuming, and thus more costly if you can't do the work yourself.

Width is another thing to consider. I can't even begin to speculate if any factory 8.5" 10-bolt is the same width as a 7.5" 3rd gen rear. You may have to get a wider rear and have it narrowed. If you're going to go to that trouble, swap the housing ends for ones that use bolt in axels and eliminate the c-clips. You'd have to get new axels made anyway, because you can't just cut and re-spline a GM axel because they are necked down.

Yet another factor is brakes. I don't know if the factory brakes can be re-used on an 8.5" 10-bolt. This could add to the cost even more.

Really take the time and figure out what this is going to cost up front. IMO the cheapest route would be to get a junk rear with no housing damage from a fullsize Chevy truck. You should be able to find one for $50, or even free if you look around. Get a blown 7.5" 10-bolt from a 3rd gen too, which should cost about the same. Figure $250 for a set of custom Moser axels. Figure $150 for weld on 9" style housing ends. Gears, Bearings, ect. should run about $300. Axel bearings, seals, and retainers are about $100. A decent posi is about $375. A girdle and studs is about $160. You'll need a conversion u-joint at about $35 (unless you get a new driveshaft made, wich runs about $250 around here). The rest of the cost is the fabrication and welding, which you would know better than I. That's about $1,370-$1,470 without a new driveshaft, and without any fab work, welding, or paying to have the gears set up. I'm not saying don't move forward with this, but I am saying take the time to really consider it before dropping any cash. A couple hundred dollars in fabrication and welding work will make a bolt in 12-bolt look very appealing.

Plenty of parts are available for the 8.5" 10-bolt. I run one under the rear of my Blazer. It's got a Detroit Locker, 4.88 gears, Warn full floating axels, disc brakes, and a TA girdle. It handles 38" tires and merciless floggings effortlessly. A friend of mine is currently running one under his Chevy II that runs slicks, a T-10 four speed, and clips mid 11s through the traps. They are a tough rear.

 

I got the SS rear for free (with disc brakes), it already has a posi, I can put the gear in my self for the cost of the gear, all I need are axles, I can gfet them from Strange for $275, and an old 7.5 inch housing to rob the brackets from.

I am hoping to complete the project, doing all the work myself for around $500.00.

Otherwise I wouldn't even try it.

 

Is the Impala rear the same width as the 3rd gen rear? If not are you planning to run different wheels to compensate?

I agree, that if you can do the fabrication and installatin of the parts yourself there is no reason not to do it. It's that whole paying people to do the stuff you can't that gets expensive in a hurry.

 

Its a whole lot wider. That is the great part. Narrowing it will be easier than widening. Right now the Impala SS rear is under an 87 Monte SS dirt track car, the tires stick out of the fenders like almost 8 inches. It looks really odd.

As for getting brackets, I just got a doner 3rdgen 10 bolt for free today! Now I have brackets and perches to weld onto the SS rear.

(The 10 bolt rear I got today is actualy off a junk V6 Camaro I gave to somebody 2 years ago, so it was free today anyway. lol!)

 

I'm doing this swap this winter. The 8.5 10 bolt out of the late 70's, early 80's camaro is about 1/2 inch shorter which is SFA.. The TA bracket may be a pain to fab, but everything else should fall into place nicely..

I paid 100 bucks (canadian) for a 3.08 posi rear end complete.. (drum brakes)

Cheers,

 

It shouldn't be too hard. Just weld it to the case. The center section is cast steel so it should weld very nicely.

 

Agreed.. If it's anything like turbine housings, it will weld nicely.. Guess I'll find out soon enough..

Cheers,

 

BOTLFED, you got any ideas for the tq arm bracket?

This is what I have so far. But any better ideas or improvements would be great. The more refined the plans are before the task is tackled the better.

I am no draftsman so bear with the pic.

 

Hrm, if anything it's a little over-built, but there isn't anything wrong with that.. It's very similar to what I had in mind.. I like the single plate in the front that goes over the snout.

With a design like that, kind of makes you wonder why someone hasn't designed and marketed a kit like this that you just need to weld on.. Hrm....

BTW, thanks for sharing, very nice job!

Cheers,

 

We'll see how hard it is to put together. Dreaming it up, and actually doing it are two differen't things.

I got the idea for the single plate in front over the snout, from Amazingmechanical that builds 8.5 inch 3rd gen rears. But I wanted to be able to used an adjustable tq arm that fits on factory style rear ends. Their single plate setup requires the use of thier tq arm.

It would be possible to make this piece from one piece of 1/4inch thick sheet buy cutting it out with a plasma cutter and forming it in a brake, and then weld it on. That would be the easiest thing to try I guess.

 

Liability. That's why someone hasn't marketed a weld on kit like this. As a manufacturer you have to be concerned about stuff like that, especially in our lawsuite crazy world. It would be easy to make such a kit, but the proffit margin on it wouldn't be high enough to justify the one time you had to go to court because some monkey thought he could weld and the weld failed and he got killed in the resulting accident. Even if you won the case you'd still have tons of legal fees.

BTW, I would weld all the corners of the multiple brackets together, as opposed to trying to form them. For one thing, you'll get a cleaner corner without a radius from the bending operation. For two, the bracket will be stronger, because no stress is being introduced into the material from the bending operation.

 

I see where you're coming from, but how would this be any different than say, a ladder bar setup? If you can't weld and put a set on your car, is comp eng. responsible? I don't know, just asking the question..

I guess the best thing to do would be to list a set of blueprints so that someone can get the plates made, or make them themselves and put it together..

I agree with your idea to make seperate plates rather than try to bend all the tabs, etc..

Very good DIY idea, can't wait to try it out..

Cheers,

 

I finally picked up my 8.5, and I realized that the brackets won't work the way I had planned because of the shape of the differential housing. So back to the drawing board.

Looks like only the front plate that gets welded to the snout on the differential housing can be used, unless the tq arm is shortened and where it mounts to the rear is moved forward, but this may cause interference with the pinion yoke.

To make things easier it may have to be done like the guys at Amazingmechanical have done it. It will require making a tq arm too. But the tq arm could be made shorter and mounted similar to the one sold buy Jegs (mounted to trans tunnle), and have an adjustable pinion angle.

I suppose one could buy the tq arm from Jegs, but its $300.00 and I can make one just like it for the cost of the heims joints. (maybe $50.00) The rest of the materials will come from the scrap bin at work. (Its a gold mine) I think I like the idea of upgrading the tq arm anyway.

 

All right. I got a new scheme. It can be made out of one piece of plate and bent to fit or cut and welded. But the Jegs tq arm will have to be used or make your own.

I will also be fabbing my own perches and brackets because the doner rear was so rusted that the brackets were too thin to use.

I will not have any dimentions till I start making the bracket, wich won't be till the first week in Feb. The ol' lady is b1tchen at me to renovate the computer room to turn it into the boy's new bedroom, got to do that first. Work, work, and more work.

 

Selling ladder bars is a bit different than a weld on torque arm mount. The ladder bars can be modified just slightly, or even not at all to be used on a wide range of makes and models. The TA mount is only good for 3rd gen F-cars. The volume of sales would probably not be enough to mitigate the cost of even a single potential lawsuit.

Are they responsible? Depends on how they worded their literature that they send with the product. Even if they aren't it doesn't mean that they can't be sued. You can sue anyone for any reason under our legal system. You might not win, but the defendant still has to mount a defense and have their lawyers in the courtroom and behind the scenes, all of which costs money. If they did a cost/benefit analysis of this product it would probably be deemed financially infeasible. Some items are only worth building by custom shops or the the do-it-yourselfer, because there just isn't enough proffit in them to justify mass production.

 

You've got some good points there, it's terrible that we have to worry about stuff like that.. Oh well, even if someone offered the brackets, I'd still make my own..

my3rdgen - I like your latest design, but it's a shame it requires a custom torque arm.. I have some ideas on how to keep the stock TA, but I'll have to go check out my rear and stare at it for a while.. It'll probably involve modifiying the old TA slightly tho..

Cheers,

 

Truthfully, the stock TA isn't that great of a design. You can't adjsut the pinion angle, and the rubber bushing in the front is inprecise. However, improving upon it requires some good engineering and fabrication. Ideally you would want a Heim joint at the front mount, and a mount on the trans crossmember as opposed to the side of the tailshaft housing. Since the front is now solidly mounted you need to have a provision for fore-aft movement of the TA or severe bind will be encountered in the suspension. You will also need adjustable LCAs to really make the system work. I've looked around at a lot of products, and IMO the one Spohn sells is the best. It isn't cheap, but the quality is superb, and the design is perfectly executed.

I think the mount would be simpler if it simply straddled the centersection instead of trying to incorporate the centersection as a structural element. It's tough to say exactly without mocking it up first hand though. One thing to keep in mind that the mount doesn't have to resist the side to side tendancy of the rear (that's what the panhard rod is for). The main objective of the TA is to control pinion angle. Everything works better with Heim joints though. Rubber bushings flex in directions they shouldn't, and poly bushings are a half-measure fix with as many cons as pros.

 

i have done this same swap in the past,i used a torque arm bracket from global west,it mounts on the rear end under the diff. cover,it has two 3/4"bars that aim towards the front of the car that mounts to the tq arm.it is held on by replacing the rear end cover bolts with 1.5"studs,the 8.5 10 bolt with moseur axles and c-clip eliminator kit will withstand 9 sec passes with 1.32 60' launches...
i have also taken the 8.5"rear end,welded all 3rd gen pearches on it minus the tq arm mount,a set of g2 LCA and welded another bar mount to the rear end housing top and put another 5/8"tube on top of the g2 and mounted it.its similar to a ladder dar set up this works very well will be more stable(solid).
this set up will get you disqualified in a stock-type suspension class,hmmm how would i know that one either way you go you can use the 8.5" and set it in the car inexpensively!

 

Yeah that's the type of TA mount I was talking about. A better approach than trying to weld to the center section, less time consuming too.

92droptopws6, is the Global West website back up? Every time I check it seems to be down. Whats the address?

 

Ditto, what's the web addy? I found globalwest.net but didn't see the product in question..

Thanks,

 

Yea, I found the website too but was not sure of the product you were talking about. I would like to see how they did it. I will still be building my own set up (it'll be cheeper) but it would be nice to see all the ideas out their before deciding how I will do it.

 

Actually this may be more simple than I first thought, using a simple piece of 1.5 X 1/4 inch angle iron bolted to the rear end cover like 92droptopws6 stated, and bolting my home made tq arm to that. It can't get more simple than that.

 

It's cast iron and welding to it is questionable.

I would make a bolt-on setup. They did so on the 87 Buick GNX.

 

Are you sure? I am not trying to start an argument, I am just going off what other people have stated etc.

This would bring to mind another question, why weld the tubes to the housing then if its cast iron? If cast iron isn't welded with proper pre and post heating, the weld WILL crack. I have successfully welded cast iron before at work, and it is a PITA for sure, but to me welding the axle tubes and taking the huge risk of a crack wouldn't be worth it if the housing were not cast steel.

I would like to know for sure if these are iron or steel before I weld the tubes in the housing. I am also steering toward a bolt on deal for the torque arm for sure now.

 

the mount i have was originally on a 86 grand national,it was made by global west,i know strange engineering makes it also but its for the 12bolt,i have had mine since 1992 been on a few cars since then!!!!!!!!go figure!

 

Me too. If anyone can send me a broken chunk off a GM housing, I can get it tested here in Phx by my metallurgist.

 

I was wondering if the grandnational rearend was close to the same width as a 3rd gen and if the shock and spring perches are in the same location as a 3rd gen?

 

the length is fine,pearches NOPE its nothing to cut them off and reweld your f-body pearches...

 

No, it's a lot narrower.