Common 12-bolt failures
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Joined: Aug 2001
Posts: 870
From: Cuyahoga Falls, OHIO
Common 12-bolt failures
For those of you that've broken Moser, Strange or KTRE 12-bolts, what specifically failed. I know they are considerably stronger than 10-bolts but weaker than Ford 9" and even 8.8" rearends but I broke mine at the track Friday night on a 1.64 60ft launch with a little over 400rwhp. I haven't had a chance to take it apart and see how much damage there is or what specifically failed, I'm just curious whats commonly goes wrong with them. I have 33 spline bolt-in axles, a girdle, Eaton HD posi and Richmond 4.10s.
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Joined: Jul 2005
Posts: 9,507
From: Okemos, MI
GM 12-bolts and Ford 8.8" rears are extremely similar. It's rumored that Ford copied GM's design. I don't have firsthand experience here, but I'm told that their breaking points are pretty much the same as well.
Both setups are generally known to withstand more than 700hp, with 60' times well below 1.5 seconds.
Not knowing what broke in yours, it's hard to really speculate, but I'd be curious to know if it wasn't assembled correctly.
Both setups are generally known to withstand more than 700hp, with 60' times well below 1.5 seconds.
Not knowing what broke in yours, it's hard to really speculate, but I'd be curious to know if it wasn't assembled correctly.
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Joined: Nov 1998
Posts: 71,098
From: Hell was full so they sent me to NJ
The only failure I've ever seen in a 12-bolt was one that burned up the clutch discs at about the 750HP level. But that was a "standard" posi unit, with the 9-disc pack, not the HD posi with the 14-disc pack.
BOOOM
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Joined: Aug 2001
Posts: 870
From: Cuyahoga Falls, OHIO
As for what broke, I'll take the cover off tomorrow, all I know is I have excessive backlash. I can turn the driveshaft about a 1/4 turn eachway before I get gear contact. I drove home at 40mph from the track that way but it was unbearably loud.
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Joined: Sep 2003
Posts: 5,907
From: The Wild West
Sorry to hear the bad news Grease. There was a guy from Cleveland who had a video of him taking all the teeth off the ring gear during a launch. I was going to buy a 12 bolt for my car, but I'm feeling better everyday about having these 9" parts lying around my room. I have read about alot of 12 bolt failures on LS1Tech.
Sad part is Darkhorse and Handyman beat their stockers to death with no problems...
-Dustin-
Sad part is Darkhorse and Handyman beat their stockers to death with no problems...
-Dustin-
Thread Starter
Registered User
Joined: Aug 2001
Posts: 870
From: Cuyahoga Falls, OHIO
Update
As it turns out, I sheared the side bearing boss right off the posi housing. I heard that this was a weak point with the 12-bolts but I never heard of someone breaking one. Its amazing that I didn't break an axle or worse. Once I took my rear cover off I could pull my ring gear back about 1/4 of an inch. Its a shame too because I just spent 200$ rebuilding the posi with carbon fiber clutches.
Anyhow, I went to a full spool and I must say its not as bad as everyone thinks on the street. I drove around most of the afternoon and would only notice it if I had the steering wheel turn full lock. Even then, its not really annoying. Plus I probably saved about 15lbs in rotating mass.
Anyhow, I went to a full spool and I must say its not as bad as everyone thinks on the street. I drove around most of the afternoon and would only notice it if I had the steering wheel turn full lock. Even then, its not really annoying. Plus I probably saved about 15lbs in rotating mass.
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Joined: Jan 2004
Posts: 1,903
From: Littlestown, PA
As it turns out, I sheared the side bearing boss right off the posi housing. I heard that this was a weak point with the 12-bolts but I never heard of someone breaking one. Its amazing that I didn't break an axle or worse. Once I took my rear cover off I could pull my ring gear back about 1/4 of an inch. Its a shame too because I just spent 200$ rebuilding the posi with carbon fiber clutches.
Anyhow, I went to a full spool and I must say its not as bad as everyone thinks on the street. I drove around most of the afternoon and would only notice it if I had the steering wheel turn full lock. Even then, its not really annoying. Plus I probably saved about 15lbs in rotating mass.
Anyhow, I went to a full spool and I must say its not as bad as everyone thinks on the street. I drove around most of the afternoon and would only notice it if I had the steering wheel turn full lock. Even then, its not really annoying. Plus I probably saved about 15lbs in rotating mass.
Imho the spool is a good call...I just went with one a month ago and I love it...I hardly know its there with the 275 60 R15 M/T radials back there, and you know for certain that both tires are pulling when you nail the throttle...I am wearing out these new M/Ts a lot faster...Oh well...I'll deal with that...
--Alan
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Joined: May 2004
Posts: 776
WOW glad to see that didn't take out the rear, you could have also gone with a Detroit Locker and gotten similar results, I've heard that spools will eventually break axles. I hope I don't have similar results with my Strange Dana 60.
Registered User
Joined: Sep 2003
Posts: 5,907
From: The Wild West
As it turns out, I sheared the side bearing boss right off the posi housing. I heard that this was a weak point with the 12-bolts but I never heard of someone breaking one. Its amazing that I didn't break an axle or worse. Once I took my rear cover off I could pull my ring gear back about 1/4 of an inch. Its a shame too because I just spent 200$ rebuilding the posi with carbon fiber clutches.
Anyhow, I went to a full spool and I must say its not as bad as everyone thinks on the street. I drove around most of the afternoon and would only notice it if I had the steering wheel turn full lock. Even then, its not really annoying. Plus I probably saved about 15lbs in rotating mass.
Anyhow, I went to a full spool and I must say its not as bad as everyone thinks on the street. I drove around most of the afternoon and would only notice it if I had the steering wheel turn full lock. Even then, its not really annoying. Plus I probably saved about 15lbs in rotating mass.
Good luck and maybe I'll catch you the next time I'm home.
-Dustin-
Registered User
Joined: Aug 2006
Posts: 3,705
From: Kansas
so, kind of off topic, but not really:
on spools, why is it that people say they are "not street friendly"?
is it just that they cant stand the whining noise when turning? Ive heard about it before, but never had to experience anything.
on spools, why is it that people say they are "not street friendly"?
is it just that they cant stand the whining noise when turning? Ive heard about it before, but never had to experience anything.
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Joined: Jul 2005
Posts: 9,507
From: Okemos, MI
When you're turning corners, one wheel has to go farther than the other, which would generally involve spinning faster. A spool won't allow that difference like a regular differential will. As a result, one of the tires will hop or slide. This is particularly non-street-friendly in wet weather or other slippery conditions, as it makes the rear end very likely to kick out.
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Joined: Aug 2006
Posts: 3,705
From: Kansas
A spool locks the left and rear wheel together 100% of the time. This means they always spin at exactly the same speed.
When you're turning corners, one wheel has to go farther than the other, which would generally involve spinning faster. A spool won't allow that difference like a regular differential will. As a result, one of the tires will hop or slide. This is particularly non-street-friendly in wet weather or other slippery conditions, as it makes the rear end very likely to kick out.
When you're turning corners, one wheel has to go farther than the other, which would generally involve spinning faster. A spool won't allow that difference like a regular differential will. As a result, one of the tires will hop or slide. This is particularly non-street-friendly in wet weather or other slippery conditions, as it makes the rear end very likely to kick out.