I know this topic has been beat to death with the wildly available and still insanely expensive 12 bolts, 9", and Dana60's around. But those are crazy expensive for 90% of us who don't drag our cars at the strip every weekend.

Thought I'd throw out this analogy. The 7.5/7.625" is basically the 1/4" drive ratchet of rear ends. Some do better than others, but with enough force and/or time, they all break. 8.5/8.625" goes to 3/8" drive and the 12 bolt would be 1/2" drive. The 9" and S60 are more like 3/4" drive. The larger you go the more torque they can take and the longer they last.

The 7.5" in our stock F-Bodies was a compromise GM made with these cars to keep the price down and fuel economy up. It worked. 300+hp LS1's with a world class T56 for $24K stock in 2002 was hard to beat and 300+hp and 26MPG in the mid nineties was unheard of. But broken axles are a quick way of making our cars slower than a Prius, but it'll use less gas! Thanks GM, but damn you!

So, I wanted to see if we can try and quantify the breaking point of our axles. We all know wheel hop kills axles, regardless of axle size or power or axle type (IRS or Live), so let's leave that out of the equation.

Second to wheel hop is ring gear walk. Traction plus power leads us to axle tube flex pulling the ring from the pinion and walking it up. This applies to auto's and manuals alike.

The other thing that breaks gears is driveline slack, auto's take this slack up with pre-load at the line. Manuals do not. So on a hard launch, even without excellent traction, all that slack is taken up in milliseconds with however much power your car is making (400hp has tremendous force even if it's only moving 1/8").

So, to quantify the breaking point. I'd like everyone who has a stock rear end to post up there best 60' times and what kind of trans they are running. This would give us a good idea of the breaking point of our dinky little 7.5" rears.

UPDATE: Please provide the following info, 60' time, girdle or not, support bars, welded tubes, gear ratio, A4 or M6, and # of passes. Thanks Guys!

UPDATED 29 AUG 15 (info from both LS1tech and LS1LT1);
Best Auto without issues: 1.375
Best Manual without issues: 1.76

Worst Auto before issues: 1.70
Worst Manual before issues: 2.1

Looks like these rears stock can handle quite a bit of abuse especially behind the auto! Those Girdles seem to be worth every penny. Hitting Sub 1.5 60' and 10 seconds on the tiny 7.5" may be the exception, but with good parts absolutely possible. Breaking an axle with a 60' time over 1.9 seconds seems to be the exception and not the rule. If they are reinforced (Girdle, solid spacers, support tubes, etc.) units they do seem to handle quite a bit more than led on....

Thanks guys!

AUTO's:
GIMPY02:.............................1.375 (A4, Vig4K, 26" Radial, Full hit from line)
TravisMcGill2000:..................1.392 (A4, 3800 Stall, Stock 3.42, 3200lbs, 28" DR's, 20 passes at 1.5x, 3 at 1.4x, 100 shot out the gate)
flathau;in:.............................1.45 (a4, Stock 3.23 rear, SS4000, 3625lbs, DR's)
JonCR96z:.............................1.469 (A4, 4K Stall, 3.90, broken, still drove ~1hr home)
jblankenship:........................1.46 (A4, torsen diff, motive 3.73, solid pinion spacer, LPW ultimate girdle with braces, tubes not welded, 3500 race weight, 275/60/15 MTs, countless motor passes in the 1.5s, at least 15 passes in the 1.4s on nitrous progressed).
Marc 85Z28 00' Trans Am:...1.48 (A4, 3700lbs, 3.73 Motives, Zexel-Torsen with LPW cover and solid pinion spacer)
Slow94Formula:...................1.48 (A4, all stock rear, 3.42 gears, 4l80e, 700-800hp, made noise after 1.48 pass)
ejbta2:..................................1.48 (200 passes at 1.62, A4, SS4000 Stall, 3.73, Hoosier DOT Slicks, LCA and Relo Brackets)
spec_j:.................................1.50 (A4, 3200 Stall, MT Radials LCAs, Adj TQ arm, Stock 10 bolt 3.23 gear no mods. over 200 passes)
NewOrleansLT1:.....................1.50 (A4, 4000 Edge Stall, 3.73, Hoosier Drag Radials)
gruntwork:............................1.52 (A4, 100% stock 3.23 rear with ~92k, SS4000, MT DR's,

 

Best I've ever got is 1.8 60, that's with 380 whp slippin the clutch off the line to save the rear. Nitto 555 DRs & 3.73 gears. I know some with A4s have gotten 1.5s but the breaking point is usually the 1.7 area.

 

have a friend that cut a 1.4x 60 in a TA with 4k stall

 

normally went 1.5x but that 1.4x was his best

 

Good info. As this thread goes I'll collect up the times into the first post for members and lurkers alike.

 

TA car or girdle? Also what gears?

Thanks!

 

Mine broke the posi around 11k miles with quite a few 1.72s or so. I think my best was 1.69. Mostly stock suspension with MT drs.

 

Thanks, added to first post. Auto? Gears?

 

1.69 60' with a yank 3600 and 3.42's on Toyo drag radials. After about 7 passes it started getting noisey and the pinion seal started leaking.

 

Sorry ! TA car and I want to say he had 323s at the time

 

1.63...full weight, built 4l65e, 3.42, DR, SS3600 (car in sig) on motor.
Not spraying off line because, well...

 

Thanks Guys, added to list. Keep em coming.

 

2.035 M6 Exhaust and a tune Stock 3.42 leaving at idle. (Didnt wanna break it) So she broke just crusin the streets. SMH!!!

 

Best i'v had is whats in the sig.

 

Added to list. Thanks!

I see a 1/4 time, I can't find the 60' time though.

 

Realized i didnt put much info in. A4, tci 3800, and quite a few 100-150hp hits. The trans and the rear broke when the 150 shot finally hooked out of the hole at the same time lol

 

I busted the rear in my '00 SS (M6; lid, catback, tuner) with Nitto 555R's off 2.1 60's (yup, that horrible even with DR's).

The rear in my '02 SS (M6) has held up fine with several 1.9 60's (lid, ported TB, muffler at the time; LCA's & LCARB) on Uniroyal all-season tires.

I've since added long tubes and LPW diff cover with ARP studs. Still running those all-season tires because I'm afraid it'll bust with something sticky as I'm making more power than my '00 while also cutting better 60's.

 

Added.

Added.

thanks guys!

 

2.03 60' 2.73s stock converter and drag radials

I will hopefully have better 60 times for ya in a week with 3.73s in my 10 bolt, yank 3600 and better drag radials

 

Thanks, Added!