Broke into the 12's

KING

KING

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Apr 6, 2013
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Took my truck to the track Sat after installing some 120 HP injectors on Fri night.

First run was a 13.3X @ 103 MPH (forgot to turn on the MP8)

Second run was a 12.77 @ 106 (real good run, 15 psi launch)

Third run was a BUST, boosted about 17-18 off launch and it scattered a u joint on the front shaft. Ended up tossing the drive shaft and ruining my t case and some other small parts.

We threw a strap on her and towed her home. Despite the expensive break, I'm still happy as hell.

Set up on truck is a 6.7 QCSB 4x4, 8500ish lbs, 6" lift on 37"s, dual cp3's, ii silver bullet 66 turbo, passenger intake horn, ii 120 hp sticks, h&s tuning 175 HD with MP8.


I'll have 4.88's loaded in it before it heads down the track again as Id like to avoid this. Plus I'll prob have the twin turbos on so it may be worse *bdh*
 
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If you're running a stock 68rfe I don't recommend too many more passes like that.
 
More gear will result in less drivetrain stress. Not saying it will keep parts from breaking, but it would help to a degree.
 
Yep Im looking to transfer some stress from the transmission and drivelines down stream of the ring and pinion.

Its got a built 68 in it. Im actually testing one for a company and they told me to try to shell it and Im about 100 hp over its advertised limit.

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Just fyi, when I had 37's on my orange F250 I went from 3.73's to 4.56's. Broke those and went to 4.30's. Broke those and went to 4.10's. The rear end guy said the ring gear was basically to small to handle that kind of power (800ish) at that weight (8300lbs). Just something you may want to check on. I rode and raced the chit out of that truck though so...

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Yeah i never thought of breaking a r&p mainly because Ive never broke a set personally. I got a smoking deal on my rears (250 nib) so i cant complain even if i do snap them!

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Yep, more teeth on the gears = reduction in strength in the gears themselves. Ofcourse, I've never given that much thought with the relatively huge rear ends in these trucks compared to the 7.5" 10bolt in my previous camaro which would break if a fly bit it.
 
Yeah some ppl have bad luck with those little 10 bolts. I had a magical one with eaton posi and 3.73 that refused to die, its been in 3 cars with hundreds of 1/4 mile passes. To this day as far as i know its still running around.
Ive seen a few of them break in 4th gen LS1 cars ( manual will do it everytime, along with a factory alum tube ds) but they usually took quite a few 11 sec passes before giving up ghost.



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imelmo said:
Just fyi, when I had 37's on my orange F250 I went from 3.73's to 4.56's. Broke those and went to 4.30's. Broke those and went to 4.10's. The rear end guy said the ring gear was basically to small to handle that kind of power (800ish) at that weight (8300lbs). Just something you may want to check on. I rode and raced the chit out of that truck though so...

.
Click to expand...

Try reducing rotating mass beyond the gears? You running 90 lb 37's? Whatd your wheels weigh?

Try setting the pinion deeper? Itll make them whine but Ive been told by many a gear man they are stronger this way (my magical 10 bolt was set this way).

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KING said:
Yeah some ppl have bad luck with those little 10 bolts. I had a magical one with eaton posi and 3.73 that refused to die, its been in 3 cars with hundreds of 1/4 mile passes. To this day as far as i know its still running around.
Ive seen a few of them break in 4th gen LS1 cars ( manual will do it everytime, along with a factory alum tube ds) but they usually took quite a few 11 sec passes before giving up ghost.



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Click to expand...

Was going to say manual trans was likely missing in that one that made it hundreds of passes. Mine in my previous 2001 camaro ss, oddly enough, backed the carrier bolts out which hit the cap and made swiss cheese. Happened when I cracked a kid in a DSM. Pulled to the light after the race and noticed odd behavior. Looked out the back of the car from the driver side door and saw a water fall coming from the rear end. One time was enough, replaced it with a 12 bolt asap.
 
KING said:
Try reducing rotating mass beyond the gears? You running 90 lb 37's? Whatd your wheels weigh?

Try setting the pinion deeper? Itll make them whine but Ive been told by many a gear man they are stronger this way (my magical 10 bolt was set this way).

Sent from my SCH-R760 using Tapatalk 2
Click to expand...


That truck is long gone. Never had an issue after I went to 4.10's though.

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NickTF said:
Was going to say manual trans was likely missing in that one that made it hundreds of passes. Mine in my previous 2001 camaro ss, oddly enough, backed the carrier bolts out which hit the cap and made swiss cheese. Happened when I cracked a kid in a DSM. Pulled to the light after the race and noticed odd behavior. Looked out the back of the car from the driver side door and saw a water fall coming from the rear end. One time was enough, replaced it with a 12 bolt asap.
Click to expand...

Nice. Yeah mine was an auto (Rossler th350) I went with a moser 9 in mine and never had an issue. Ive helped pull some mangled ones though. Kid paid me a grand one night to do it in a parking lot lol.

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