Hi All:
I have an interesting situation someone might be able to help me with.
I recently purchased a '76 '6 at an auction, thus was unable to get
any information from the previous owner (both a good and bad thing!).
When I took possession of the car, the spedo cable was not attached,
nor included, among other things. In trying to debug the car and get
everything functional, which included rebuilding the clutch twice, I
noticed that the trany was not original, nor was even a '6 trany.
Prefixes match to a 2000 trany.
I finally received a replacement from TRF (Thanks guys), hooked it all
up (including disassembly the EGR counter and lube), and was all set
to go. To my suprise, on the commute to work the next day, what I
thought was a reasonable 65-70 mph speed, confirmed through numerous
prior calculations, indicated 80+ mph on the spedo. Closer inspection
indicated that the spedo is ~20% OVER actual speed in 4th at all revs.
The only way I can understand this situation is that the spedo thinks
the car is moving faster that it actually is. This situation
generally occurs when UNDERSIZE tires and/or gears are substituited
for the original. For tires, I am actually running 215/70-15's, ~1%
OVERsize. I assume the diff has not been replaced, something I can
check, but a change to 3.45 gears cannot account for this large
difference.
Can anyone shed some light on the situation???? I am willing to recal
the spedo, and can swap in a known working backup, but I don't
understand the situation. Given the LARGE tire size on the '6
compared with all of the TR models, no change in gearing can
counteract the tire diameter gain to create an undersize situation.
I need help!
Scott Mackay
Austin, TX
|