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Old 06-20-2007, 07:37 AM
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7.5 rear end ???

I accidently purchased a second rear end the same as what ive already got. A 7.5 10 bolt. I thought i was getting atleast an 8.2. I notice that jegs sells all the gear choices as well as posi's and lockers for the 7.5. Here is my question. If i were to build a 7.5 would it hold up to a 450 hp sbc? I want to run 373's in the rear end. Im a little nervous about this build as i dont see axles for my application listed at jegs if i were to break one. Much less putting the money into something i wont be happy with or be able to keep running.
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Old 06-20-2007, 11:17 AM
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You didn't list what the rearend application is, but Moser makes axles for a lot of the 7.5" 10 bolt rearends. They run about $235 a set and are much better then stock.

I don't know what to tell you as far as it holding up - I think it depends if you are using slicks on a heavy car with a lot of drag racing or if it's a street car that sees the occasional hard launch. I have used a 7.5" in a dirt circle track cars when rules dictated it - broken mini-spools and c-clips, but that was a pretty rough environment. I believe these rearends were in the LS1 F-bodies so they will take some abuse.
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Old 06-20-2007, 11:43 AM
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I would also consider adding a differential girdle to support the main caps.
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Old 06-21-2007, 07:02 AM
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The car is a 77 nova so its pretty light. I plan to keep it a street car but i like to play so street or strip i wont be running slicks and it will see some abuse. And what is a differential gurdle? And where can i get one. Sorry if im asking dumb questions but this is my first real performance build. The moser axles listed in Jegs does not list one for my 77 it only goes up to a 76. But maybe they would make a set for me. I think if i decide to go for it i will use my stock axles first. Thanks for all your help and patients with a rookie.
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Old 06-21-2007, 07:14 AM
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If you call Moser they already know exactly what size your axles are. You tell them what your vehicle is and they can tell you how much and how long for delivery.

If you do not use slicks, the stock axles might hold up. I have seen 7.5's with slicks running high 12's.

The girdle mentioned is a replacement cover on the axle. It is beefier and has a couple of set screws that put preload on the carrier bearing caps to strengthen them. It also helps to dissipate heat better too.
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Old 06-21-2007, 09:27 AM
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Weak link

Hi,
I have a 76 nova that is a street/strip car and i was in the same situation you are now, but i had a mild 383, TH-350, and had the stock 7.5. I choose to go with upgraded 3.73 gears and girdle, i was also using cheap BFG tires tires, they were 275/60/15 but just spun, so the rear end lasted about 4 months behind it with. THE FIRST TIME i took it to the track and actually got a decent launch, left axle snapped. No problem, had a spare at the house, was able to race the rest of the day after some repiars. Lasted maybe 40 passes at the track after that, including some street driving that was not launching or full throttle, then during a burn out before making a pass at the local track, the spider gears gave up and demolished everything inside except the gears. If your on a tight budget and want to save some money, its not a bad option in my opinion, i ended up going with a 8.5 after this and have made 100+ passes on slicks without any issues.

Just something to think about.

ALSO if your looking for some 3.73's for that 7.5 i have a set not being used. PM me if your interested as i have no use for them.

Robby

Last edited by 38376nova; 06-21-2007 at 09:34 AM.
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Old 06-22-2007, 06:43 AM
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I want to purchase an 8.5 the problem for me is finding one. I had found one out of a 70 nova that they tried to sell me but i believe this one is longer then mine and wont bolt right in due to spring location and what not. Would it be worth it to get the 70 nova rear and try to fit it for my application? I dont know that i trust anyone to do any welding for me and i only have a small welder and need alot more prctice before i try such an important piece. Atleast with the 70 it should be a posi and save me the $400.00 jegs wants for a spool or a posi. Hey Idea lol if the 70 nova rear is a few inches longer per side that might be ok for running a wider tire as long as i move the perches if needed. What do you guys think could that work?
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Old 06-22-2007, 11:11 AM
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You may have found something

From what i have gathered over the years, and from this site you should be able to use the rear end from a earlier nova, some one correct me if I'm wrong, but i believe that the rear end is the same from the first gen Camaro,and the second and third gen Nova. I believe its the First gen Nova and the second or later Camaro that will not fit as the camaro is 1.5 inches wider i believe? witch may be able to be made up with backspacing if necessary.

http://www.novaresource.org/axle.htm is a great site for ANY information you will need on your nova. What i did is i bought the rear with a posi carrier for a hundred bucks or so, and rebuilt it with gears, seals and whatnot. Comes out pretty cheap. (go to that link and it will give you actual dimensions to measure before you buy, trust me measure... if your not looking up the axle code that is.

Thanks for reading, let me know if you need any more sites for your nova.

Last edited by 38376nova; 06-22-2007 at 11:26 AM.
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Old 06-23-2007, 11:57 AM
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Thats the sight i went off of when i bought my rear for $100.00 my rear has the four points like the 8.5 in there pic almost. the bottom 2 are pointed on mine not square like those. I should've measured and i didnt. I also should've known that when you ask the owner of the yard a question and you get "I dont know" that he is looking to sell you something you dont want because he knows your nieve enough to do so. Boy did i get took on that deal. I'll have to post the difference in the two for others. And yes im always looking for more sights everyone on here has been good about combining their efforts its really cool. Thanks for all your help 38376Nova
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Old 06-23-2007, 12:31 PM
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The 7.5 will live in a 12second Nova if its built right. That means you have to start from scratch. New posi, new gears, new bearings, rear cover support, solid pinion bearing spacer, new Moser axles. You could also do all this to a 8.5 Nova rear to good effect. Do not get a spool if the car will be street driven at all.
Wheel hop and a lack of traction is a major cause of broken driveline parts.
Make the car hook solid on launch and your rear will last a lot longer reguardless. And you'll go faster.
I recommend this bolt on traction device for your Nova.
Caltrac traction bars
They flat out work.

Last edited by F-BIRD'88; 06-23-2007 at 12:52 PM.
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Old 06-24-2007, 09:19 AM
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Everything F-BIRD'88 said is very true, but IMO if you build the 7.5 you will still have to worry about it later, build the 8.5 and your done. The solid pinion spacer instead of a crush sleeve is something i also did in mine but i have not had side by side comparison to show the difference.

Wheel hop is bad on these cars especially if you put air shocks on it or try to raise the rear for bigger tires.( witch is not necessary i put more then enough under mine and its lower then stock.) Some type of traction bars is a very good idea.

But if you have a 450 HP car and 3.73 gears depending on where your HP curve is set up, i doubt you will have enough traction to get wheel hop on the street at all, the main area i have problems is doing burnouts. other then that on the street i cant get enough traction to actually get wheel hop.

Also, if your looking to put a lot of tire under there i have a 8 By 15 weld rim with a 4.5 inch backspacing and it gave me a lot of room after "rolling" the fender lip.

Don't feel bad about getting the wrong rear end i ended up doing the same my first time around. Just learn from it, and don't do it again. Pretty expensive mistake.

Have fun and keep us updated on your project, I'm always interested in a x body.

Thanks
Robby

Last edited by 38376nova; 06-24-2007 at 09:26 AM.
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Old 06-25-2007, 06:37 AM
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I'm wanting to run the original height tire and as wide as will fit in the fender. I dont want to have speedo issues, I thought a mickey thompson like the S pattern would grip pretty well on the street. But i am a long way from wheels and tires. My biggest problem is money. Motor is done minus a starter now i need headers, torque convertor, rear end, tranny, just to name a few of the bigger ticket items.
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Old 06-25-2007, 10:53 PM
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Buck up and get an 8.5" to spend your money on. Hop-up parts cost the same for either one, and a used one shouldn't be over $100.

Any '73-'79 Nova 8.5" rear will bolt into a '77 Nova. Springs & shocks are all in the same place. Look for V-8 cars after '74, although there were a few 305 cars that had 7.5's one year (1976, I think). You will need to have the driveshaft shortened, most likely, but if you get the shaft from the donor car, you could save yourself that hassle. If your current shaft physically fits, be sure it has at least 3/4" of yoke sticking out of the back of the trans. You don't want it bottoming out in the trans when the suspension compresses.

If you plan to really beat on it, get the axle tubes welded to the center section while it's out, so they won't slip around and cause leaking and squirrelly handling. Get the spring perches welded to the tubes if they're not fully welded from the factory. Get the U-bolts from the donor also, and use them. Two U-bolts on each side, much better than the T-bolts.

ID for 7.5" vs 8.5" is here: http://www.oldsmobility.com/10bolt-tech.htm

Last edited by jimfulco; 06-25-2007 at 11:02 PM.
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Old 06-29-2007, 12:22 AM
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go get a 8.5!!! dont use that 7.5! it will blow up!!! but the 8.5 will hold up to 500HP with a good posi and strong gears in it! but go to novaresource.com to find out the interchangablility of rear ends for your car!!!
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Old 06-29-2007, 03:32 AM
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7.5 rear end ???

I can tell you from personal experience that when the 7.5 blows up it does lots of damage and comes to a stop real quick.I went to a custom made Ford 9 inch that was a bolt in,now I have one less part to worry about.
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