How To Break a 10-Bolt

[Naaman]

Knowing that the 10-bolt is the weak link in our cars, is there any info on the circumstances of these things breaking?

I imagine that the vast majority (99%, maybe?) break as a result of high rpm clutch dumps.

I also know that there are those out there who drive around with a gazillion horsepower and "have no issues" with their stock 10-bolt. I suspect that driving habits are the main factor.

Anyone care to hazard a guess at what the 10-bolt can actually take? Suppose the car is putting 400 to the wheels? Full throttle from a 15-mph roll? Full throttle in 2nd gear and up only?

[Firebirdjones]

It's really a crap shoot Naaman. I've broken these things with stock power. Usually the Torsen diff or an axle. Never had any issues with the pinions. Another weak link is the gears, with everyone wanting to install steeper gears. Big mistake with these things. The ring diameter is too small, so as you increase gear ratio and the pinion shrinks, the tooth contact pattern is diminished. I've seen quite a few 4.10's with the teeth shaved off.

I'll admit you do have to try. Most cases on stock tires it's not much issue unless you get on a really well prepped track. Otherwise spinning is the best thing for it. Sticky tires can make short work of the rearend IF you drive the car like you want the best ET out of it Low rpm launches and granny shifts don't count.

If you have a stick, I'd highly recommend looking at a good rearend upgrade.
I've never felt I could have much fun with these cars until the rearend was upgraded, no matter what was done to the engine.

It was GM's biggest mistake with these cars. They stuck with it because they were too cheap to tool something better. The predecessor of these torque arm 7.5's is the 75 and up Monzas. These rears were junk in the 70's, they continued in the 3rd gen Camaros with no improvements, and they haven't really changed since.

[Naaman]

Yeah, that's where I'm at. I'd like to slap a 12-bolt or 9-inch in there, but... money! I'm thinking I'll baby it until I have the money saved up and in the event that it fails, I'll upgrade it. What I'm hoping is that it won't break under "spirited driving." I don't do launches. The hardest I ever drive my car is a WOT burst in 1st from about 2500 rpm.

[Whamhammer]

It's really a crap shoot Naaman. I've broken these things with stock power. Usually the Torsen diff or an axle. Never had any issues with the pinions. Another weak link is the gears, with everyone wanting to install steeper gears. Big mistake with these things. The ring diameter is too small, so as you increase gear ratio and the pinion shrinks, the tooth contact pattern is diminished. I've seen quite a few 4.10's with the teeth shaved off.

I'll admit you do have to try. Most cases on stock tires it's not much issue unless you get on a really well prepped track. Otherwise spinning is the best thing for it. Sticky tires can make short work of the rearend IF you drive the car like you want the best ET out of it Low rpm launches and granny shifts don't count.

If you have a stick, I'd highly recommend looking at a good rearend upgrade.
I've never felt I could have much fun with these cars until the rearend was upgraded, no matter what was done to the engine.

It was GM's biggest mistake with these cars. They stuck with it because they were too cheap to tool something better. The predecessor of these torque arm 7.5's is the 75 and up Monzas. These rears were junk in the 70's, they continued in the 3rd gen Camaros with no improvements, and they haven't really changed since.

I was suprised they kept with the 7.5/7.65's too, especially since there are tons so S10's and S10 Blazers running around with low-po engines and 8.5's. They even put 8.5's in many of the hi-po' G bodies, which (except for the turbo Buicks) were not more hi-po' than a mid-level F body.

[Naaman]

Speaking of other rear ends, what's the most affordable way to upgrade the rear end? If I could get a 12-bolt for under $1000, I'd be all over it.

[2002ssslp]

I you find a 12 bolt for under 1,000 bucks it will have a sold tag on it already. Get yourself a good set of Richmond gears and roll the dice while you save up 3k for a Strange S60 rear.

[Naaman]

What is it about Richmond?

I've been hoping there would could find one second hand... but Google doesn't even seem to know what I'm talking about...

[kingls1]

I you find a 12 bolt for under 1,000 bucks it will have a sold tag on it already. Get yourself a good set of Richmond gears and roll the dice while you save up 3k for a Strange S60 rear.

He couldn't have said it any better, IMO the s60 is one hell of good rear end choice for these cars, it is a very stout unit and extremely well built. You have to replace the drive shafts with them due to the size of the case so there is another link in your drive train that is bullet proof. I couldn't be happier with my choice in the s60 it runs and drives like a brand new car with "0" gear noise. Some complain about the 20 lbs of weight it carries over a 12 bolt but I can tell you this I have been to the track three times once with the 7.5 and twice with the s60 and have gone faster with the s60 by far. 1st - 2nd time were on street tires so the launch were about the same or even less rpm's the second time due to loss of traction due to gearing change but still went faster. This last trip was on NT05R's and I was coming out at over 3K rpm's and it was awesome. I went with the 4:10's with the m6 and couldn't be happier with how it drives. Wife and I just took it on a day trip and put nearly 300 miles on it on one tank of fuel. Around town it's got a lot of spunk but on the highway it's better than ever with only a 400 rpm increase at 70mph I can now lug it down to almost 55 with out down shifting and still have the power to pass just about anything at any time. Another member on here went with 3:73's at the same time I did mine and he too is completely satisfied with it.

[Firebirdjones]

Goodluck finding a 12 bolt that cheap If you find them for a grand let me know I'll snag them up

I sell them for $2,000 a pop used here all day long. Usually advertise them for $2500 and don't have any trouble selling them.
Even had people wanting mine out of the car because the car is forsale, and offering me $2k on the spot to take the rear out, lol.

[Firebirdjones]

He couldn't have said it any better, IMO the s60 is one hell of good rear end choice for these cars, it is a very stout unit and extremely well built. You have to replace the drive shafts with them due to the size of the case so there is another link in your drive train that is bullet proof. I couldn't be happier with my choice in the s60 it runs and drives like a brand new car with "0" gear noise. Some complain about the 20 lbs of weight it carries over a 12 bolt but I can tell you this I have been to the track three times once with the 7.5 and twice with the s60 and have gone faster with the s60 by far. 1st - 2nd time were on street tires so the launch were about the same or even less rpm's the second time due to loss of traction due to gearing change but still went faster. This last trip was on NT05R's and I was coming out at over 3K rpm's and it was awesome. I went with the 4:10's with the m6 and couldn't be happier with how it drives. Wife and I just took it on a day trip and put nearly 300 miles on it on one tank of fuel. Around town it's got a lot of spunk but on the highway it's better than ever with only a 400 rpm increase at 70mph I can now lug it down to almost 55 with out down shifting and still have the power to pass just about anything at any time. Another member on here went with 3:73's at the same time I did mine and he too is completely satisfied with it.

If you don't have a radical cam, you can lug these things waaaaay below 55 in 6th gear without downshifting with the stock 3.42's.. They go down to 35 mph easily and can pick up speed from there. I have a mild cam in mine and even with the 3.42's I could drive around town in 6th at 35-40 mph no problem. Now with 3.73's 30 mph is a piece of cake in 6th. I've never had to downshift it to pass anything on the highway, still has plenty of guts.

[Firebirdjones]

Naaman, I'd leave the stock rear alone and just hang on, stay in touch with Sean and those guys down there, those guys wheel and deal on stuff all the time, and eventually a good used rear pops up. It won't be as cheap as you're hoping but you'll still save a few bucks over having a new one shipped to your door.

[Senator]

I broke mine twice, both times with less than 400 HP, both times with 4.10 gears, both times the ring gear broke on moderate acceleration while turning.

Tried lowering the LCA front attach point, replaced the torque arm with a real one - not the stamped pot metal it came with, Bilstein shocks and Eibach springs to try to control wheel hop. Nothing worked.

Then I bought a Moser 12 bolt. No more issues.

Regards,
Darden

[Naaman]

He couldn't have said it any better, IMO the s60 is one hell of good rear end choice for these cars, it is a very stout unit and extremely well built. .

Yeah, I've kinda accepted that fact since there does not seem to be a used market for rear ends.

Goodluck finding a 12 bolt that cheap If you find them for a grand let me know I'll snag them up

I sell them for $2,000 a pop used here all day long. Usually advertise them for $2500 and don't have any trouble selling them.
Even had people wanting mine out of the car because the car is forsale, and offering me $2k on the spot to take the rear out, lol.

Do you pull them out of acquired cars or...?

Naaman, I'd leave the stock rear alone and just hang on, stay in touch with Sean and those guys down there, those guys wheel and deal on stuff all the time, and eventually a good used rear pops up. It won't be as cheap as you're hoping but you'll still save a few bucks over having a new one shipped to your door.

That's kinda what I'm thinking, too. I'd like to make it as simple as possible and as "excusable" as possible to beef up the rear end.

I need it to be able to handle 400-ish whp (after I put on headers, I'll probably be done with the build as far as power goes).

I broke mine twice, both times with less than 400 HP, both times with 4.10 gears, both times the ring gear broke on moderate acceleration while turning.

Tried lowering the LCA front attach point, replaced the torque arm with a real one - not the stamped pot metal it came with, Bilstein shocks and Eibach springs to try to control wheel hop. Nothing worked.

Then I bought a Moser 12 bolt. No more issues.

Regards,
Darden

I was thinking that a torque arm would make it more likely to break, no? Doesn't it "improve" the power delivery to the rear? I have 3.42s now, and I like the gear ratio because I like the tallness of the gears (especially 2nd gear). So I'd probably keep those in.

If I get the wheels and tires that I want, the rest of the build will be brakes, torque arm, new LCAs and new shocks (these are getting worn out).

[Whamhammer]

I broke mine twice, both times with less than 400 HP, both times with 4.10 gears, both times the ring gear broke on moderate acceleration while turning.

Tried lowering the LCA front attach point, replaced the torque arm with a real one - not the stamped pot metal it came with, Bilstein shocks and Eibach springs to try to control wheel hop. Nothing worked.

Then I bought a Moser 12 bolt. No more issues.

Regards,
Darden

I bet 4.10's on a stock rear were probably very small teeth on the gears too, that wouldnt have helped either.

I went from stock 2.73's to Richmond 3.23's on my old TPI T/A, ended ip having some of the teeth brake loose on that one. Talk about WTF factor!

[Whamhammer]

Yeah, I've kinda accepted that fact since there does not seem to be a used market for rear ends.



Do you pull them out of acquired cars or...?



That's kinda what I'm thinking, too. I'd like to make it as simple as possible and as "excusable" as possible to beef up the rear end.

I need it to be able to handle 400-ish whp (after I put on headers, I'll probably be done with the build as far as power goes).



I was thinking that a torque arm would make it more likely to break, no? Doesn't it "improve" the power delivery to the rear? I have 3.42s now, and I like the gear ratio because I like the tallness of the gears (especially 2nd gear). So I'd probably keep those in.

If I get the wheels and tires that I want, the rest of the build will be brakes, torque arm, new LCAs and new shocks (these are getting worn out).

Dont forget the panhard rod.

[pajeff02]

We upgraded our car to a Moser 12 bolt and pound on it good at the track whenever the opportunity arises. If I had to do it all over again, I would have probably went with the Strange S60 as ours is a bit on the noisy side and the Strange is about as bulletproof as you can get. With 33 spline axles, welded sway bar mounts and a True Trac the 12 bolt stickered for $2,800.

[Firebirdjones]

The most recent Strange 12 bolt I just bought, with all the goodies added, was $3200 delivered to my door. That's the 33 spline C-clip eliminator axles, Eaton posi, US Gears, support girdle cover, extra $$ for the Billet 1350 yoke, not the standard cast or forged stuff, and they all come with the larger 9" ford bearing ends, and more stuff I'm forgetting. Another nice thing I like about the Strange rears that Jeff touched on, they have welded sway bar mounts, not cheap muffler clamps like some brands I won't mention here They also take the time to weld on factory style brake line tabs, a small detail but I like details. Other companies expect you to zip tie or band clamp your lines on, lol. Cheeesey.

It's about as bulletproof as you can make a 12 bolt. They are stronger than the original GM 12 bolts from the start anyway as they are aftermarket castings, the main cap webbing area is beefier, The caps are billet and much larger than stock (factory are cast iron), axle tubes are larger, they are stout pieces. You definitely get your money's worth.

I put this behind a 6-speed, and I have no worries what so ever that rearend will ever give me an ounce of trouble for the rest of my years, and will outlast the life of the car, probably shoved under another car and outlast that one too.

Besides the fact it's leading an easy life with my wife daily driving it, she doesn't pound on the car. But it's piece of mind that it's in there in case the day comes I want to have a fun track day with it.

Yes Naaman, usually what pops up available is something that was in another car at some point. Usually the cars may be wrecked, or a project that never got off the ground. Sometimes cars are de-modded to sell.
Even I may go that last route as ours is forsale. If I can't get something close to $10k for it the rearend will come out, original 10 bolt will go back in and I'll sell the Strange separate, because I won't be giving the rear away with the car. I know they are an easy sell for $2k all day long. Hell this one doesn't even have 5,000 miles on it, and it's quiet as a mouse. But with the calls I'm getting lately on the car I suspect I won't have to do that.
Matter of fact one of the previous 12 bolts I bought second hand. It had a spool and 30 spline axles and things I just couldn't use on the street so I completely revamped it with an Eaton posi, 33 spline axles, new gears etc...all brand new stuff. But sold the car before I got it done. I sold that rear for $2k and it was gone in a week. Wound up under another 4th gen down in the valley somewhere.

Whamhammer, yes you are right. When you install 4.10's in the little 7.5" rears, the contact between the ring and pinion is horrible. You only get about 1 and a half teeth that contact at any given time because the pinion shrinks in diameter with 4.10's and the ring gear diameter isn't large to begin with. Very common to strip the teeth right off of it. Steep gears just aren't meant for these little rearends.
When you have factory 3.23's or 3.42's you have about 2.5 to 3 teeth contacting at all times, so you can see it's a very big difference in strength just in the ring gear alone. 3.73's only have about 2 teeth contacting so even that gear is reducing it's strength abilities. Simply put, I just refuse to install gears in these 7.5's. Just not worth it.

[pajeff02]

^^ That is one thing I was bummed about on our Moser, no tabs for the brake lines.

[Naaman]

Dont forget the panhard rod.

Already have it, but thanks for the heads up. The LCAs are just old. Plus they are noisy rod-ends. I'm looking at swapping to a poly/roto combo from UMI. Though I can't seem to get a straight answer on how noisy the roto-joint is compared with a rod-end/Heim joint.

The most recent Strange 12 bolt I just bought, with all the goodies added, was $3200 delivered to my door. That's the 33 spline C-clip eliminator axles, Eaton posi, US Gears, support girdle cover, extra $$ for the Billet 1350 yoke, not the standard cast or forged stuff, and they all come with the larger 9" ford bearing ends, and more stuff I'm forgetting. Another nice thing I like about the Strange rears that Jeff touched on, they have welded sway bar mounts, not cheap muffler clamps like some brands I won't mention here They also take the time to weld on factory style brake line tabs, a small detail but I like details. Other companies expect you to zip tie or band clamp your lines on, lol. Cheeesey.

Yes, I like details too. And I like quiet... other than for the parts that are supposed to make noise. Even still, I like a reasonable noise level... not obnoxious. Haha!

[Naaman]

Just learned something new:

The S60 is not a 12-bolt or a 9-inch...