A 2007-08 SRX, STS, 2008 CTS equipped with 6L50 (RPO MYB) automatic transmission may have no forward or reverse or no input or output speed signal after valve body installation or replacement.
According to bulletin 09-07-30-005, this may be caused by the installation of the incorrect center support fluid passage seal or upper valve body assembly. The center support fluid passage seal for the 6L50 is approximately 5/16 inch (8 mm) taller than the seal used on the 6L80 / 6L90 (fig. 19).
The 6L50 seal can also be identified by the metal tabs or wings extending from the ends of the seal. The shorter 6L80 / 6L90 part will not seal the valve body to the center support resulting in an internal fluid leak.
A Seal for 6L50 is taller
B Seal for 6L80 / 6L90 is lower
C Seal for 6L50 has tabs
Also, the 6L50 upper valve body center support oil transfer holes are in a different location than on the 6L80 / 6L90 valve body (fig. 20).
Installation of the 6L80 / 6L90 upper valve body may result in an internal fluid leak with no forward or reverse.
A Hole location for 6L50
B Hole location for 6L80 / 6L90
Finally, installation of a 6L80 / 6L90 upper valve body will not place the input and output speed sensors close enough to their respective drums to generate a speed signal. The bosses are milled at different heights (fig. 21).
A Bosses for 6L50 taller
B Bosses for 6L80 / 6L90 lower
If these conditions are encountered, check the P/Ns used in the repair to verify that they are the appropriate parts for the 6L50 (MYB).
Upper valve bodies can be identified by observing the machining of the small posts in the illustration (fig. 22).
The post is milled to indicate A, B, C or D.
Post Corresponds to
A not currently used
B MYB / 6L50
C MYC / 6L80
D MHD / 6L90
- Thanks to Mike Johnston
According to bulletin 09-07-30-005, this may be caused by the installation of the incorrect center support fluid passage seal or upper valve body assembly. The center support fluid passage seal for the 6L50 is approximately 5/16 inch (8 mm) taller than the seal used on the 6L80 / 6L90 (fig. 19).
The 6L50 seal can also be identified by the metal tabs or wings extending from the ends of the seal. The shorter 6L80 / 6L90 part will not seal the valve body to the center support resulting in an internal fluid leak.
A Seal for 6L50 is taller
B Seal for 6L80 / 6L90 is lower
C Seal for 6L50 has tabs
Also, the 6L50 upper valve body center support oil transfer holes are in a different location than on the 6L80 / 6L90 valve body (fig. 20).
Installation of the 6L80 / 6L90 upper valve body may result in an internal fluid leak with no forward or reverse.
A Hole location for 6L50
B Hole location for 6L80 / 6L90
Finally, installation of a 6L80 / 6L90 upper valve body will not place the input and output speed sensors close enough to their respective drums to generate a speed signal. The bosses are milled at different heights (fig. 21).
A Bosses for 6L50 taller
B Bosses for 6L80 / 6L90 lower
If these conditions are encountered, check the P/Ns used in the repair to verify that they are the appropriate parts for the 6L50 (MYB).
Upper valve bodies can be identified by observing the machining of the small posts in the illustration (fig. 22).
The post is milled to indicate A, B, C or D.
Post Corresponds to
A not currently used
B MYB / 6L50
C MYC / 6L80
D MHD / 6L90
- Thanks to Mike Johnston
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