The 5L40-E and 5L50-E transmissions and valve bodies look the same at a glance. On the Cadillac, Pontiac Solstice and Saturn Sky, you can look on the service-parts identification label to identify the transmission by the RPO (Regular Production Options) number.
In the past, manufacturers of low-volume vehicles such as Rolls Royce and Jaguar used GM transmissions and A/C systems rather than design and develop their own. The trend has enlarged and continued so that the automakers looking to cut costs and increase efficiency are relying more on their tier-one suppliers to design and develop complete components such as transmissions and transfer cases. This has created a growth in units of a common design now showing up in many different vehicle platforms, from U.S.-built to imported brands.