M74/MW7 Allison LCT1000 PTO Gear Applications - keywords noise transmission whine

This PI was Superseded to update Recommendation/Instructions. Please discard PIP3083E.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Some 2004-2007 Chevrolet Silverado and GMC Sierra classic pickup trucks and 2007-2008 Chevrolet Silverado and GMC Sierra pickup trucks equipped with Allison LCT1000 transmissions do not have PTO gears installed on the rotating housing. Instead, they have a tone ring for the turbine speed sensor that does not have the ability to drive a PTO (power take-off).

1. All 2001-2006 8.1 L18 (VIN code G) and 2001-2004 6.6 LB7 (VIN code 1) engine equipped trucks will have the PTO gear installed from the factory and has the ability to drive a PTO if desired.
2. All 2004-2008 6.6 LLY (VIN code 2), 2006-2008 6.6 LBZ (VIN code D), 2007-2008 6.6 LMM (VIN code 6) and 2007 8.1 L18 (VIN code G) engine equipped pickup trucks will not have a PTO gear installed but will only have the tone ring.
3. All 2004-2008 6.6 LLY (VIN code 2), 2006-2008 6.6 LBZ (VIN code D), 2007-2008 6.6 LMM (VIN code 6) and 2007 8.1 L18 (VIN code G) engine equipped chassis cab trucks (models *C36*** or *K36***) will have a PTO gear installed. Trucks with box delete option, RPO ZW9, do not have a PTO drive gear unless they are 2007 and prior model years equipped with an 8.1L, L18.

If a customer desires to use a PTO on a pickup truck equipped with a LLY, LBZ or LMM 6.6 engine, it will be necessary to install a rotating housing that has a PTO gear installed on it.

Part numbers for the rotating housings are:

2005 Model Year and older 29540518

2006-2008 Model Year and future 29542802

This would not be a repair covered under warranty and would be at the customer's expense.

Important:  For new body style 2007 and 2008 Model year vehicles that do not have the PTO option, installation of the rotating housing will ONLY allow a stand alone mechanical PTO to be installed but WILL NOT allow integration with the rest of the vehicle (Reference the latest version of PIT4334).

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.