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Discussion Starter · #1 ·
I have a 12 bolt rear with stock axles, and 3.73s. I very much want to take my car to the track for the first time ever and cannot afford to upgrade my axles at this point in time. I am looking for some opinions about this being is that I recently installed a 496 with 575 hp 585 tq, and a th400 with slicks. (I have a driveshaft loop)
I would only take it to test and tune one time this year, and hopefully be able to upgrade the axles in time for next years season. I would think I should be okay for maybe 2 passes? Any thoughts? :p
 

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All it takes is one Dead Hook // that is where the Tires donot Spin some or a little ON Launch
I have seen this happen at the Track when there is to much HP/TQ for the Drive Train
and the Launch Pad is Sticky

What size are your U-Joints ? if smaller than 1350s then they may break before the Axles
 
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Discussion Starter · #3 ·
All it takes is one Dead Hook // that is where the Tires donot Spin some or a little ON Launch
I have seen this happen at the Track when there is to much HP/TQ for the Drive Train
and the Launch Pad is Sticky

What size are your U-Joints ? if smaller than 1350s then they may break before the Axles
Hmm, good point I didn't even think of the u joints til you mentioned. Honestly I'm not sure the size I'll have to double-check
 
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It all depends on how you launch. If you leave at or near idle you are probably fine. If you take the engine up to the torque converter's stall speed and it hooks maybe not.

Sent from my SM-A716U using Tapatalk
 

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Discussion Starter · #5 ·
It all depends on how you launch. If you leave at or near idle you are probably fine. If you take the engine up to the torque converter's stall speed and it hooks maybe not.

Sent from my SM-A716U using Tapatalk
I was planning on leaving at 1400 rpms, or idle. After 1400 my rear tires break free from the brakes, I do not have a line lock
 

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You should be just fine leaving at an idle. Four speed or a trans brake would be a different story. Saw a friend hit a stock 12 bolt on numerous passes with a th400 468 and a brake. Ended up eating up the ring gear before anything else.
 

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You will likely lose the quarter panel at a minimum if it breaks
 

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What is needed for a drag racing application? I thought 12 bolts were supposed to be strong?
 

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What is needed for a drag racing application? I thought 12 bolts were supposed to be strong?
12 bolts are strong for stock engines. It's cheaper to go with a Strange S60 or Moser 9" rather than try to upgrade a 12 bolt for racing.
 
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A 12 bolt is strong if it's built correctly. The stock axles are tapered and thin near the splines. Good after market axles are the same diameter for the full length, and made of better material. Some of the cheaper after market axles may not be any better than stock axles.
 

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You have 1310 stock ujoints. I kept that size when I upgraded the Denny's shaft, 1.) as I did not want to change the pinion yoke, and 2.) wanted the ujoints as my weak link, to Kirk's point.

Years back I upgraded to Superior axles, which like Fred says, are thick across the entire length. Now I am puckered up on not having the tubes fully welded. Where does it end!?

You'll have NO issue with a few passes, unless you try to dead hook and get air.
 

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Discussion Starter · #13 ·
Thank you all for your replies, I think I'm going to make a couple of light passes off idle this year. Only going to take it to the track one time this season.
Over the winter I'll upgrade the axles, and next years season is when I'll try launching for the sky lol
I do like the idea of keeping the u joints as the weak link even with better axles.
 

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1970 El Camino SS396, VortecPro 467, ATI TH400, Moser 12 bolt /TruTrac 3:42, Hedman headers
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Consider a full aftermarket rear if your motor makes the power you indicate, Moser style 12 bolt, 9” Ford or Strange style S60 and with 1350 U-joints and good axle studs. Avoid C-clips, broken axles, ripped up quarter panels and trips into the guard rails.
 

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I do like the idea of keeping the u joints as the weak link even with better axles.
hey, I am NO ENGINEER , but it simply made sense to me. Its my AXLES TUBES I am getting puckered up on. 600 ft lbs on slicks with a clutch drop isnt easy on things. Viscous couplings, aka torque converters can really help.
 

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Gene, if you are abusing a Chevy 12 bolt that much then an upgrade to Moser, Strange or Mark Williams 12 bolt would be a very good idea. Even if your axle tubes are holding up, you are putting a lot of stress on the left bearing cap and bolts. The after market housings have thicker caps, larger bolts, thicker axle tubes and the tubes are fully welded. You also get stronger axles with 9 inch Ford type bearings and no c clips. I've installed a few Moser 12 bolt rear ends lately with 33 spline axles and Truetrac.
 

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Discussion Starter · #18 ·
I was originally looking into these from summit, along with an aluminum rear differential cover with the load bolts that support the caps.


Th400 with 3.73s leaving the line at idle or 1400 rpms, maybe hold up for a car that will see the track maybe 2 to 3 times a year just for test and tune? Nothing serious.
 

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Freddie, its sure not a bracket car with a stick shift! More like budsthe3 a few times a year cadence.

PS is that why the shim pack was trying to extricate itself from the left cap? I found it last time during my once a year 12 bolt diff inspection. They're in quite snug to boot.
 

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I've got a 9 inch in my Camaro with a nodular case. My 427 doesn't make as much power as your engine, and I stretched the 1/2 inch bolts on the left bearing cap. It's a wonder that it didn't break the cap. It caused the backlash to change. I only race my car 2 times a year. It's not the number of times you race, but how hard you are on the parts on one run. The 12 bolt only has 7/16 bolts.
 
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