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Author Topic: Anyone else ever had a broken input shaft??  (Read 268 times)

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Anyone else ever had a broken input shaft??
« on: April 17, 2019, 13:14:26 PM »

So asides from the lift, gears, tires and programmer my Avalanche is basically stock with regards to the engine, aside from it being brand new 1 year ago.  The trans is built with plenty of upgrades.  So my question is, has anyone else had the input shaft on their trans snap?  I have had the output shaft break already once and it took out the front pump and a bunch of other stuff at that time as well.  The trans was just rebuilt in January of this year under warranty due to the planet bearings going so everything was fresh at that time.  The shop said it snapped right at the journals (four cross drilled holes in the shaft for lubrication) but that it is VERY rare that they break.  The shop also stated that with the gearing I currently have in there (4:56) is better for the drive train than stock.  I wonder if with the shift kit, corvette servo and the programmer all bumping line pressure up and stiffening up the shift points is causing it, maybe I need to tune out torque management and abuse mode so that when it shifts under load it will break the tires loose rather than hitting as hard as it does.  Any ideas or input?
2007 Graystone metallic, Amber LED DRL's, all LED lights on exterior, 6" Pro Comp lift, 35x12.50 Amp terrain grippers, Cali offroad 20x9 anarchy's 4:56's K&N FIPK, Bully dog GT Tuner, Color matched front and rear bow ties, 6000K HID low & fog lights, Rampage fire and ice tailgate light bar, led light bar on the sails, Sirius satellite radio, Compustar Pro 2 way, color matched Bushwhacker pocket style flares. LS460W Dash cam


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Re: Anyone else ever had a broken input shaft??
« Reply #1 on: April 17, 2019, 14:38:18 PM »

You should soften up the shifting to stop breaking hard parts.

When I first rebuilt my truck's transmission I had it chirping the tires on 1-2 shifts.  The output shaft broke within a week.  This was with the original engine (cammed).

After rebuilding it again I reprogrammed the computer to soften the shifts.  It now sits behind a 460 hp crate motor that I added a supercharger to.  It's been behind that combo for 2 years.
2003 with ATK 460 HP 6.0, Speed Engineering Long Tube Headers and true dual 3" exhaust, Truetrac rear, 3200 Circle D Stall, tranny upgraded with 4L65 and other heavy-duty parts, Weld Racing 18x10 forged wheels, HPTuners custom tune, Vortech supercharger, water/meth injection, Magnavolt fuel pump voltage booster, DeatschWerks booster fuel pump, 58#/hr injectors, 13.3 @ 101 in the quarter mile.
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