Rob Nanzig writes:
<< Kelly's question about overdrives got me thinking about a situation I am
about to create.My SV came with a 4.22 rear end which I am replacing
with a 3.89. What do I need to do to keep my speedometer/odometer
accurate?>>
Rob,
Keep speedo accurate? Dunno if it ever is but Rick at Sunbeam Specialties
sends tachs and speedos to a place in New Mexico, I think, to recondition
them. I sent my tach to him and it came back really accurate and steady.
Maybe they can recalibrate the speedo to give an accurate reading based on
rear end ratio, OD/nonOD and maybe tire size. Anyone know?
BTW, I also replaced the 4.22 with 3.89 and this spring installed an
overdrive. I found that the speedo read almost exactly 1.5 times the actual
speed, i.e. read 90 mph when on a measured mile I was going about 60
(actually 58). It was a thrill to see the speedo go just past 120 in
Montana on the way to SUNI even though I knew it was really about 80.
BTW2, Reminder for Rob or anyone else pulling their differential: when you
do be sure to check the tightness of the ring gear bolts. Most likely you
will find them barely hand tight. There is discussion on this topic in the
list archives, it is worth your while. Also, Jim Leach has a bolt
replacement system for your peace of mind.
Rob Carpenter
Series V/3.89/OD/not a slug in Seattle
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