that's because the 2.8 wasn't offered in 87. based on that mistake, there's no way to know the ratio for certain without either popping open the cover and checking the stamping on the ring gear, or spinning the drums around and counting the times the yoke spins.
-88 MJ; 4.0L, ex-2wd, TJ ax15/231, 78 Ford D44 w/spool, 9" w/posi, 33" trXus MTs, custom roll-bar/bumpers/etc.
Also an 86 MJ Metric ton and 2 '90 MJs
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