7.5 / 7.625in. Rear End - Overall Discussion

[patmckinneyracing]

Figured I would bring this up as I know that with my 2400 stall, 700r4 first gear, and 3.73 rear gear, I'm gonna be having some traction issues with the new setup. The 700r4 is running larger boost valves, corvette servo, shift kit, and larger/stronger components, so I'll be chirping or just spinning tire.

I'm running a 7.625 rear out of an 86' Monte SS. It is fully built with Yukon gears and stock auburn posi. I plan on getting a girdle cover as well. I know that the prior generation camaros and WS6 firebirds from the 90's and up until 2000 or so used the same size 10 bolt 7.625 rear end as well. I've seen plenty of the camaros and WS6's running around with drag radials and slicks on the street and strip. There's a lot of them in my Texas State Gearhead Club and none of them blow rears as some have warned me by running slicks.

So I want to discuss some of the factors here. Is the whole weakness myth of the older 7.625 rear coming from people throwing slicks/drag radials on a 25+ year old rear end? Are the rears from the camaros/firebirds running better internal components, or are they identical to one another internally? I try to throw in the age and human factor together because we all know of someone who threw in a massive engine with a 30 year old trans or rear end and blew one of the two, which could result in certain parts getting a bad rap.

I had my rear rebuilt and never had a problem rompin on it and doing burnouts at the strip. This thread is meant to discuss the rigidity, pros, and cons of this rear. Lets also discuss how to make this rear end better and stronger, let it be from aftermarket gears, c-clip eliminators, or a girdle cover. Thanks guys.

 

[jrm81bu]

All the 7.5's i've broke were spider(side) gear related, posi or open. I never had slicks or drag radials on any of them, just street tires. Also none of the ones I broke were with the supercharger in front of them. I think the weakest point is the spiders and axles. I still don't believe that any g-body 7.5 had 28 spline axles. I know you are certain you have 28 spline axles stock in your rear, but none of the 7.5's had them in 86. So the only real upgrade would be a 28 spline posi and axle uprgrade. Everything after that will only marginally help.

The newer f-bodies had 28 splines and the 4th gen(94-02) had the zexel torsion posi unit. I'm not sure that any of the late 3rd gen f-bodies got the same posi unit. This is one of the reasons they will handle more of a beating then our g-body 7.5's. That said they will still break them, it's never if but when with a 7.5.

One of the things you can't change is the diameter of the pinion shaft, it's fairly small. That will still limit aftermarket gears.

C-clip eliminators will keep you from wrecking or destroying your quarter panel, but the don't stop it from breaking or increase the strength.

To try to answer some of the questions you listed. Yes, the newer f-body rears are built with better internals. Sure the age has to play at least a small role, but how much is the question. Human factor, well ya, neutral dops never help. I think doing donuts or sliding around a corner or side-to-side burnouts are harder on the spiders than a straight line burnout. I tend to keep mine in a straight line anymore.

While I will admit that they can be built to handle a decent amount of power, the question becomes, is it worth it? There is no doubt that you will hit a limit of what a 7.5 can handle. I think money spent on a different diff, 8.5, 12 bolt, 9 inch will usually be money well spent. After all how many of us think we have enough power, and don't have the desire to make more?

 

[jimmyp618]

Ok this is what i did to mine and it so far is holding up to 493hp. 7 5/8 out of a camaro 50 buck jy,moser 28 spline g/n axles.225.00 . A set of 3.42 gears used 50 bucks so about 325 bucks for a rear to hold that much on drag radials for 2 yrs has been well worth it. transmission is a th400 w 9.5" stall. Some poeple disagree with how they will hold up ,but really know one knows , you just have to take your chances.

 

[pontiacgp]

I had the 7.5 auburn and blew up the spiders...the pinion spiders in the auburn are significantly smaller than what's in an open. If I was going to keep the 7.5 I'd get upgraded axles and run a locker so the pinion gears and side gears are gone. I was going to build a ford 9" but I found a 67 chevelle 8.2 rear end with a 3.08 posi for $600. It's 2.5" wider than a 7.5 rear so it's give me a wider stance in the back and my wheels will fill the wheel opening better

 

[Tuggy24g]

To sum it all up. Most people have blown up a 7.5 gbody rear quiet easily. Other have not broken theres yet or at all. So it is take your chance. Build up a 7.5 that might break or build up a 8.5/9inch and know it will not break.

 

[olds307 and 403]

The reason the 28 spline is better is not just using the GN axles, suprised they fit a 7.5". The 7 5/8" rear has the larger spider gears, which would definitely help. I have broke a chunk out of my no slip, where the C clip drops in, the weakest spot. Still functions. I have the 7 5/8" carrier just needing bearings on the shelf. They may get replaced and a 7 5/8" 26 spline lock right, less trouble than the no slip. We will see in May with drag radials.

 

[patmckinneyracing]

So far my luck has held up quite well with both the 7.5 and 7.625. My stock 2.29 7.5 rear held up to me doing j-strips, neutral drops, and whatever else I could do to it. I was literally trying to break it because I didn't have anything as far as acceleration with the new motor and trans. Luckily, I found my 86' Monte SS rear at a local swap meet with auburn posi and all for $200. The only issue I had was after 5 months, it chipped a pinion tooth, which I wasn't surprised with it being a 24 year old ring and pinion. Other than that, it has held up very well with no problems. But I know Yukon's quality is very good and is much better than stock ring and pinions, so that probably helped out.

As far as my rear having 28 spline axles, yes it has them, but more than likely that its probably from one of the previous owners working on it.

 

[Blake442]

Believe it or not, the '85-'88 Monte SS's came with 28-spline axles in their 7.625...
They were the only g-body 7.5/7.625 rears to get them.

I'm not worried about the 7.5 in my car, the wagon doesn't make enough power to break it...

 

[jrm81bu]

Believe it or not, the '85-'88 Monte SS's came with 28-spline axles in their 7.625...
They were the only g-body 7.5/7.625 rears to get them.

I'm not worried about the 7.5 in my car, the wagon doesn't make enough power to break it...

I still have yet to see anything that states that though. Everywhere I look for replacement parts lists them as 26 spline. I just doesn't make sense since none of the other body lines had 28 spline(7.5) carriers or axles til 88-89. I'm not saying I know they didn't but can't find anything concrete on it. And I can't tell people to upgrade their axle with a 28 splin set out of a Monte if I can't find anything the states they had them.

 

[pontiacgp]

there was some 7.625 carriers that had the larger opening for the 28 spline axles but they were only found in the F body..

7.5/7.625" trivia...
83 & 84 Monte SS, 3.42:1 gears. Posi not available on '83 SS.
85 - 88 Monte SS, 3.73:1 gears.
26 spline axles.