Do all 2001 8.1l Chevrolet Suburbans have a 4.10 axle ratio?

No, not all 2001 Chevrolet Suburban 8.1L models had a 4.10 axle ratio. While 4.10 was a common ratio, particularly for those equipped for towing, other ratios were available depending on the specific options selected by the buyer (like a towing package). You'd need to check the vehicle's build sheet or the sticker on the driver's side doorjamb (if still present) to determine the axle ratio of a particular Suburban.