2.76 was the stock ratio with automatic transmission in the years ('70-'74) the 198 was offered.

To check the rear axle ratio accurately, chalk the inboard sidewall of the tire that'll turn and block the other tire (or don't lift it up) so that it can't turn even a little bit. Trans in Neutral, parking brake released. Turn the marked tire through two full revolutions and count quarter-turns of the driveshaft by watching the rear U-joint caps as they come to face the pavement. Divide the number of quarter-turns by four to get your ratio.

16/4 = 4 = 3.91
14/4 = 3-1/2 = 3.54 or 3.55
13/4 = 3-1/4 = 3.21 or 3.23
12/4 = 3 = 2.93 or 2.94
11/4 = 2-3/4 = 2.71 or 2.76
10/4 = 2-1/2 = 2.45
9/4 = 2-1/4 = 2.26

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Could be wrong, but I think you get inaccurate ratio's if you block one tire. Something about the spider gears turning.

I've always jacked up both wheels and turned the driveshaft. Count the number of times the tires turn to get one rotation of the driveshaft, there's your ratio. Always made sure both tires where turning, though.

Maybe I'm missing something, don't do it very often. Just stick in my head as a problem.

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'15 Chrysler 200S V6
'74 Duster 360, factory 4 speed car

Nope…you get an inaccurate count if both wheels are off the ground (because of the spider gears), and you get a really inaccurate count if both wheels are on the ground! You just need to make sure you turn the one unblocked wheel through two full turns, not just one.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.