1979-1993 & 94 Conv [Subscribe to Daily Digest] |
RF,
consider yourself doing 65 mph (104.6 kmph in the rest of the world) ACCORDING TO YOUR SPEEDOMETER (not to a GPS, not to a speedgun). With #7 (32:25 teeth = 0.78 ratio) sprockets and in the V gear you'll be revving at 2660 rpm. I picked up #7 sprocket-set since it's a common stock primary drive for turbo C900. Ok, here goes the same speed and the same V gear for different sprocket-sets in the primary drive:
set #4 (quite unlikely to be found these days, appears to be used in 4-speed transmissions only) 31:30=0.97 ratio: 3300 rpm
set #5: 30:27=0.90 ratio: 3070 rpm
set #6: 31:26=0.84 ratio: 2860 rpm
set #8 (very rare to find, darn expensive to buy): 33:24=0.72 ratio: 2455 rpm
At lower speeds the difference will be less noticeable. Higher speeds are illegal on public roads (as far as they tell).
Shorter ratios give you better mid- and top-speed acceleration (e.g. from 40 to 60 mph or from 60 to 120 mph) and provide less stress to the clutch. Longer ratios give you the top speed (if your engine is healthy enough to meet it) and lower rpms on the highway. Also, there's a theory, that longer ratio improves fuel consumption, but it turns out to be more complex and not that obvious as at the 1st sight.
So it's up to you whether it is worth it or not. If you quite often find yourself missing VI gear, then shorter primary drive isn't for you - look for a longer one (greater #N-value on the sprocket-set). If you don't use V gear any often, then it's worth going shorter.
Zig
P.S.
Anticipating the next question coming: it is the 3rd digit from the left (well, and from the right as well!) - GMxxDxx - on the gearbox model which designates the primary drive aka the sprocket-set.
posted by 188.134.44...
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