My two cents:

I've learned two things about those. First thing, was dealers carried them for pocket change, giving me a clue they expect them to break. Learned that from reading this forum, not from experience, preferring to collect a few of them from the yards after someone had harvested all the odo gears.

Second thing, on the electronic gauges (like your 91 and 93) I tried in vain, with the gauge on the bench, to catch the odo gear being moved by a trip reset, yet I've stopped two odos by using the reset parked at the gas pump. I'm still running vintage odo gears -- haven't yet given Jeff my $25 -- so I'm into the math exercise too. Actually I just write the odo reading on the gas receipt. After 10 years driving the same cars one gets to feel if the m's pg are wrong.
--
Art Benstein near Baltimore

My dog is worried about the economy because Alpo is up to $3.00 a can.
That's almost $21.00 in dog money.
-Joe Weinstein