The Problem
According to the TSB PIP 3136Q, the 2007, 2008, 2009, 2010, 2011, 2012 & 2013 GMC Sierra, 2003 – 2006 GMC Sierra Denali and the 2003 – 2007 GMC Sierra Classic have a myriad of mechanical issues that can cause slipping, delayed or missed shifts in second, third and fourth gears. These issues may be caused by premature wear to the 2-4 band and/or the 3-4 clutch. However those issues can be caused by a number of other issues, which we will outline now!
What Transmission Do I Have?
Low line pressure
Cracked or broken 1-2 accumulator piston
Damaged 2-4 servo piston seals
Scored 2-4 servo apply pin
Scored 2-4 servo piston bore
Servo feed oil passage blocked with sediment
Damaged forward clutch apply piston seals
Cracked forward clutch apply piston
Damaged turbine shaft oil seal rings
Turbine shaft check valve retainer and ball assembly (if the check ball is missing, it’s gone inside of the torque converter, and the torque converter will have to be replaced)
Damaged 3-4 clutch apply piston seals
Cracked 3-4 clutch apply piston
Blocked 3-4 clutch and forward clutch oil feed passages
Damaged overrun clutch seal
Leaking or unseated 3-4 clutch check ball and/or #7 check ball
Undersized 4-3 sequence valve
Stuck boost valve
Damaged input sun gear to input carrier thrust bearing
Cracked or damaged oil pump body
Damaged forward sprag
Worn or damaged rear stator shaft bushing
Out-of-spec transmission pump cover
The TSB does say that if none of the above problems are found to be the root cause of the failure, then the input housing, forward clutch piston and 3-4 clutch piston should be replaced. If the 2-4 band or 3-4 clutch prematurely fails again, then the entire transmission should be replaced.
What Transmission Do I Have?
Smart money says, if you are having problems related to this TSB, then perhaps you should go ahead and just simply replace your transmission now. A remanufactured 4L60 transmission from Street Smart Transmission has all of these issues already addressed, along with a number of meaningful upgrades that will keep your truck on the road for a very long time. To learn more about the Street Smart Transmission difference, click here.
