From some research I think the 722.3 has been made starting sometime in the late 70's or 80's. They were used in the S class for all engines. The 722.4 came later and was used in the smaller cars. So I gather from what you are saying that the 722.5 is a 722.4 with a 5th gear. I made the mistake of putting a 403 ci engine in a mid 80's Buick Riveria FWD which only came with a 300 ci or smaller. Yes that 403 would brake the front axles if you were not careful. Is there a 722.XXX overdrive for the bigger engines that you know of?

Thanks Paul

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84 500 SEL (307,xxx miles)