Ok I would like to know the approximate strength of a Grand National rear vs a Ford 9" I currently have a stock GN 8.5 rear. I'm in the process of building a g body car to drag race. I would like to know if it would be better to beef up the GN rear or sell it and use the money to build a ford 9". The car will weigh about 3400 with me in it and have about 800-850 HP and about 750 lbs/ft of torque. What would I need to address with the GN rear to make it live behind this type of power. I currently am running this motor, although detuned to 680HP and 680lbs/ft, in a 4000 lb GS with a 12 bolt and detroit locker. I have moser axles and c-clip eliminators along with 5/8 studs in the 12 bolt. I foot brake the car with a tight 3000 stahl convertor. It has gone high 10's in full street trim. I'm looking to transfer this motor and trans into a g-body and shoot for low 10's or hi 9's. Should I ditch the GN rear and build a ford 9". Any guidance would be appreciated.
A Gbody 8.5 will hold it for awhile, but if used regularly, experience tire shake, or using Radials will expedite its demise. I certainly would weld the tubes, narrow it a few in and go to large bearing ends along with support braces out the lca mounts. All this along with a spool and a girdle will hold the power no problem. Now if all the fab involved in doing this isn't something you can do you will better off to buy a bolt in 12bolt or 9in but they too will require good parts to live a long life not just retrofitting stock stuff
At that torque and horsepower level I would upgrade the rear. I think that would be asking to much of it.
The GN rear would need to be upgraded for safety (axle retention) which would destroy its value for future use as a donor for restoration. They make reproduction rears in all styles (9", dana, 12 bolt), but that is what they are: REPRODUCTION. Although I've never had the need for one, I would go with an aftermarket 9". The 9" is less mechanically efficient than a GN 8.5" rear, but the 9" can handle more power. That is just foer STOCK based configuration; aftermarket has even more potential for both. There is MUCH more parts support, more gear ratio availability, etc. I haven't priced stock GN rears in several years, but they were going for over $1200 then. I imagine that they aren't any cheaper... My vote= aftermarket 9"
9" 1) go here http://www.quickperformance.com/ 2) select rear and options and provide the delivery address where you want it shipped to 3) provide credit card info 4) bolt it right in about two weeks later
The 8.5" will handle it when built correctly.I did one for a friend's 71 Camaro that runs 9:20's @ 3200lbs. It has a spool and all the race candy. Will you be driving this on the street? If not,then get a 33-spline spool,put the good housing ends on it(not c-clip eliminators),custom 33-spline axles,billet yoke,girdle cover,and let it eat. I am currently building a 71-72 8.5" to go into a 79 G-body,with a 496.He already has an A-body rear in there,so he already has the control arms for that swap. If the rear is in good working order,you could sell it to find a new aftermarket rear. If you did sell it,I would get a Moser 12,or a Strange Dana 60,but that is just me.You can get either one of those with a housing made for a G-body. I assume this is stock style suspension,not back-halved,coil-overs,etc.
I had good luck with mine until I got into the 9 second zone. First it started killing ring and pinions and then the Eaton Posi exploded some spider gears at the 2015 NMCA Muscle Car Nationals. Since I drive my car to the track, I did not want to deal with another tow truck episode. So, I went with the Strange S60 rear end. I could not be happier. It is indestructible and a great price for what you get too.
Weld the tubs first, install 9" axle ends on, buy a rearend girdle that is adjustable to housing bearings, and run double adjustables upper and lower control arms. Then have a damn good shop adjust the control arms to your ride height. Many guys in x275 have retained 8.5 rear and ran some very ridiculous numbers and still able to street drive them. Call Carrie rear ends,Mark williams enterrises, Strange Engineering, Moser engineering, or even Calvert Racing suspensions. These guys will help you any way you can possible think. It depends on if your running in class of racing or just plain going to the track and drag racing for fun. You have to pick your poision. But the GN rearend is very strong, its in the suspension tune that really matters if its gonna break or not. Remember, bandaiding only goes so far.
Thanks for the input guys. I too have gone thru most of the parts in my 12 bolt, some a couple of times. I broke the ring gear bolts a few times, exploded the moroso brute strength posi unit and even snapped all the wheel studs on the left side. Luckily, no damage to the car. I will probably go with a 9" because of parts availaility, and being able to just order what I want is convenient too. Might be willing to unload this GN rear to offset the costs some, so if you know anyone looking. Its a really clean, stock housing. I had it blasted and painted it with rustoleum. Its been in my heated garage since, probably 5 years now. I'm in NE Ohio. Thanks Mark
Did you get yours yet, I'm looking forward to the pix. I don't plan to run faster than mid 11s so I'm staying with an 8.5 with bolt in axles . I doubt mine will run in the 13s right now but I have big plans. Only time and money stand in my way.
Hi Rich, I could have bought it three times now but priorities seem to sneak up. I got detoured again to build another engine that is most deserving the QP 9". It is the next order once the engine is in the final assemblisy stage..TARGET is early April....stay tuned. :TU: Low 11's is the dial in...N/A not bad for a row down the track or to the grocery storeo No: Now I am worried about the bully built Rock Crusher lasting but my guy thinks he's confident it will take it:Brow:
Definitely sell your original 10 bolt 8.5 to someone needing a restoration rear and build any AFTERMARKET 9" Dana 60 12 bolt chevy rear. If you truly are knocking out those number do not get a stock 9" center you better get a beefed up large pinion 9 I can price out rears as I get deals from Moser. I will not build the 9" I can price them out direct from Moser and give you the best discount I can get. Jim J D
Also consider the S60 rearend I believe they make a direct fit for the G-body You won't have to worry about things pulling apart and grenading transmission nor rear like what can happen even with a built 9
This is exactly what I did for my 1987 442 with SBO DX based power. Sold the stock 3.73 posi for $1000 & put the $ towards the Quickperformance 9" with rear disc brakes. Money well spent.
Why will you not build the 9" Thats all I ever see and hear is "Put a 9" in it" Just wondering. When I get closer I will get ahold of you for pricing. I like that your local too, kinda. Thanks Mark
Why will you not build the 9" Thats all I ever see and hear is "Put a 9" in it" Just wondering. When I get closer I will get ahold of you for pricing. I like that your local too, kinda. Thanks Mark
They are all good rear if built correctly... All I am saying is They are more of a headache for me to build in a GM car as I have to approach everything different. It is like McDonalds...Thy make everything and it is all just ok at best... I do not want to be McDonalds. I will stick with my GM rears and build them the best I can...Everyone else loves the 9" as they are easy to build and everywhere. IE Small block Chevys are plentiful too. does that make them the best motor ever made? They are everywhere, easy to find parts and cheap to build... does that make them the strongest best motor ever? I am bias to GM rears... My pet peeve when I started all this was to get 9" rears out from under GM cars. That is what drove the business at the beginning...Proving a 10 bolt rear can handle a lot more than most give it credit for and showing people that 9" FORD is just a 10 bolt rear..Period. Any rear will do a great job if given a good rebuild...too many times I have seen New motors and transmission teamed up with a Used 12 bolt or even used 9" etc. then it fails and guys say they just have too much power!!...lol. That rear was just old and tired. Just because it spins and does not make noise does not mean it is top notch condition. So to answer the why do not build 9" complete rear ends...Too much time for me to build my own to fit GM product and time is money... I do what I do best GM rears. As stated I will rebuild any 9" or Mopar third member, No problem. It is just the custom housing etc i do not want to spend time on as there are TONS of other guys and businesses do it already. I am already buying Moser 12 bolt housings and build them as 12 bolt Chevy housings and swap meets and other are just getting hard and TOO expensive to buy and most are pitted and bent too. Buy the time you get it all cleaned blasted and straightened time and labor is very close if not more than a Moser superior 12 bolt housing. Have a great weekend. Jim J D
Jim I purchased a rear off of you about 5 yrs ago. It is an 8.2 posi. I never installed it and it has been sitting in my heated garage. Any interest in trading it towards a moser rear build for my G body or do you know someone that might be interested in it. thanks Mark
Hey -- for all you guys running the later ('80S) GM rear --- I have unearthed six (6) sets of N.O.S. ++ Asbestos ++ Rear Brake Shoes.... Two years ago, had 4 sets -- sold all 4 sets @ GMs @ Carlisle -- and lost sales on more!!!!! This year,had 7 sets!!!! --- NO Grand Nationals there -- did sell 1 set to an '87 Monte Carlo.... The Grand Nationals --- R E A L L Y need them with their special brake drums!!!! Don't want to "rip them up"......
