Phasing Drone Or Growl Noise With TCC Applied - keywords bodygroan moan noise shudder surge valve valvebody vibrate

This PI was Superseded to add build month and add to the administrative details. Please discard PIP4079.

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

Some customers may comment on a phasing, drone or growl noise. This noise will typically be heard when the transmission is in 6th gear and engine speed is in the 1,300 - 1,600 RPM range.

Use a Tech 2 to monitor and snapshot transmission data. Review the snapshot while watching TCC slip speed while at constant throttle. If the slip speed cycles from approximately 0 to 60 RPM in a fairly even frequency the transmission is operating normally and is reacting to variation in the engine RPM. This engine RPM variation is more evident between 1100 and 1500 rpm, with a green engine with low miles, and will be worse in higher ambient temperatures and when regular fuel is used rather than the recommended premium fuel. Make sure the vehicle is using premium fuel and allow at least 5,000 miles to accumulate before re-evaluating this condition. If the vehicle was built prior to May 2007 please contact TAC at the number that you have been provided.

If the TCC slip speed varies from 0 to at least 100 RPM or greater consistently when at constant throttle there is a concern with the transmission. Remove the lower valve body and inspect the TCC regulator apply valve (355) for free movement and the presence of debris or machining chips that may prevent the valve from moving (SI document 1645206).

1. Remove the valve from the valve body.
2. Once valve is removed inspect for any scratching or scoring.
3. If any is found then the fingernail test will need to be performed.
4. Use your fingernail to move over scratches to see if nail will try to catch on the scratch or score.
5. If so then valve body will need to be replaced.
6. It has been found that in most cases that the scratches are not severe enough to catch your fingernail.
7. In this case the valve should be cleaned with some type of contact or brake cleaner.
8. The bore should also be cleaned. Clean with machined side down so debris may escape.
9. Blow off with shop air.
10. To verify free movement of the valve, dip into clean ATF and install valve back into the bore, the valve should move freely. If the valve moves freely, in most cases the valve body will function properly when reinstalled.
11. Reassemble and retest.

If the valve body assembly is removed from the transmission the electrical connector seals (9, 10), fluid pump seals (18, 19), center support seal (20) and the filter plate assembly (311) should also be replaced. These parts are included in the filter plate kit P/N 24236934

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.