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The AERA Technical Committee offers the following information on crankshaft replacement caution for 1998-2003 GM 4.3, 4.8, 5.3, 5.7 and 6.0L engines. Design changes in the flywheel flange thickness have been made to some crankshafts used in the above-mentioned engines. This bulletin is being re-published with additional information.
The later crankshafts are shorter on the flywheel flange as seen in the listing below. These changes are due to the many different vehicle / transmission combinations being built by GM.
A flywheel spacer ring GM Part #12563532 and a longer bolt set GM Part #12563533 is required when using a thin flange crankshaft to replace a thick flange crankshaft. Also, if the crankshaft is being used in a vehicle, which is a standard shift application, you also need pilot bushing GM Part #12557583 or 12479894.
All GEN III crankshafts used in Camaro, Corvette and Firebird have a .857 thick flange and also have a freeze plug installed at the bottom of the pilot shaft hole. The 4.8, 5.3 + 6.0L don?t have the freeze plug. The drilled hole thru the centerline of the 5.7L LS1 & LS6 crankshafts allows a path to balance crankcase pressure within the lower crankcase. Doing so has eliminated possible oil consumption when the engine is operated over 4800 RPM.
Caution: Early crankshafts use a flat reluctor wheel and late have a recess. Recess will work on all years. Do not use a flat reluctor on late applications as it will cause an engine misfire.
I received a motor from a junk yard and it was a 2007 Silverado 2500. It appears to be a LQ9 but I cannot be certain since the vin was burned up. Can anyone tell from this picture and the casting number. It looks flat to me but there is a little recess in the piston not sure if that is enough to be considered dished ? 12576184
I received a motor from a junk yard and it was a 2007 Silverado 2500. It appears to be a LQ9 but I cannot be certain since the vin was burned up. Can anyone tell from this picture and the casting number. It looks flat to me but there is a little recess in the piston not sure if that is enough to be considered dished ? 12576184
Run of the mill LQ4. That ring around the outside with the lowered center is a 7 cc dish. However I need to cc one of those with the valve reliefs because it should be more than the earlier non valve relief variant that I have checked and they are 7 cc. The pistons in the 2006 and 2007 LQ4s have the same valve relief the VVT equipped LY6 and L96 (and the half ton truck variant L76) 6 liters came with of course being Gen IVs. No your engine is still a gen 3 but for whatever reason they switched the pistons early. The 2004 calendar year and 2005 LQ4s have the same piston minus the valve reliefs but came with full floating pin rods as well.
Oh yeah.. if it's out of a 3/4 ton truck its never anything but an LQ4 as a gen 3. The LQ9 was reserved for specialty "performance" oriented applications only.
Casting number means nothing other than it's a 6 liter. Good necro thread dig lol.
08-17-2014, 01:29 PM
