07 Yukon 4L60E no 4-3 downshift
- Thread starter fruitbum
- Start date
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Tahoe14
Full Access Member
Maybe Nick at @NickTransmissions can help.
@fruitbum
- Any codes/engine light on?
- How long has this been happening?
- any recent trans work (if so, what has been done)?
For anyone else w/the same or similar issue (OP hasn't been seen since Sunday afternoon) - You need to see what commands the ECM is giving at the time when accelerating heavy while in 4th. Next step would be plugging a bi-dirctional scan tool into the OBD2 port and taking it for a test drive. Monitor the transmission data streams for downshift commands. If the command is being issued and nothing's happening then start looking at solenoids (A/B), 3-2 downshift, input speed sensor (if equipped - they were introduced in 2006), valve body and servo. If they all check good, something's failing inside the case.
Also check other sensors/switches such as TPS, MAF, etc...they can impact transmission performance/behavior.
- Any codes/engine light on?
- How long has this been happening?
- any recent trans work (if so, what has been done)?
For anyone else w/the same or similar issue (OP hasn't been seen since Sunday afternoon) - You need to see what commands the ECM is giving at the time when accelerating heavy while in 4th. Next step would be plugging a bi-dirctional scan tool into the OBD2 port and taking it for a test drive. Monitor the transmission data streams for downshift commands. If the command is being issued and nothing's happening then start looking at solenoids (A/B), 3-2 downshift, input speed sensor (if equipped - they were introduced in 2006), valve body and servo. If they all check good, something's failing inside the case.
Also check other sensors/switches such as TPS, MAF, etc...they can impact transmission performance/behavior.
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