Is the RM rear axle the same as the Cadillac Fleetwood rear axle?

I’m assuming it is as as they are dimensionally so similar.

Depends upon the Roadmaster. Sedan? Yes. Wagon? No. Fleetwood has the same narrow frame as the sedans while all wagons have the wider frame. Fleetwood also uses a different rear because they had 4 channel ABS on them.

Sedan and Fleetwood--1566MM

Wagons--1642.5MM

Source is this thread. https://www.impalassforum.com/threads/rearend-widths.237620/

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