In my '55 1st Suburban, with a GMC 270, SM420 and 3.08 gears in the rear, got almost 18 on a recent highway trip running 60 and 70 mph.

Tires are 235/70-15s and it cruises nicely at 70. I was surprised to do that well, I expected more like 16.


1955 1st GMC Suburban | 1954 GMC 250 trailer puller project | 1954 GMC 250 Hydra-Matic | 1954 Chevy 3100 . 1947 Chevy COE | and more...
It's true. I really don't do anything but browse the Internet looking for trouble...