Yes, the '74 has a lower rear gear, but comparing the overall gearing of a
manual versus automatic is a bit more complex. We're really comparing apples
n' oranges. I made a general statement that the '74 has a taller gearing
when I probably should have said a taller overall first gear. The '74 has a
7.89:1 first gear versus the '75s 7.74:1. Because of the nature of many
variables in the design and application of automatics there is a fudge
factor to consider. It's unfortunately not a constant, but if I remember
correctly it's about 1.13 on average. 1.13 x 7.74 = 8.514:1, somewhat lower
than than the '74. Once the car is launched, ratio comparisons become a moot
point because of the inherent difference in design philosophies. Pugs says
that his comparisons between a '74, '75 showed the '74 a clear winner,
implying that for whatever reason, R&T was short shifting.
GM
-----Original Message-----
>Guys,
> I am not sure why everyone wants to say that the gearing in the 74's
>was taller than in the 75's.
> If the rear end ratios are 3.15:1 for the 75's and 3.54:1 for the
>74's then the 75's have the taller ratio. As for overall ratio i find
>it hard to believe that a 4 speed manual has taller gearing than a 3
>speed automatic (especially if the cruising rpm in the 75 auto is less
>than the 74 4spd.) and therefore the 74 should have a low overall
>gearing and a definate advantage in 1/4 mile times (but may run out of
>gear for top end)
> A shorter gear will be faster than the taller gear (as long as it is
>not too short). (The 3.54:1 w/4spd should not be too short.)
> Assuming that the 74 had more horsepower and better gearing (and
>should have been approximately the same weight) it really should have
>been much faster (in the 1/4 mile and on the roll but maybe not top
>end).
> If the 75's were really faster there must have been a real
>shortcoming of the 360 AMC motors like a very short torque curve or no
>horsepower after 4400 rpm (as mentioned below). The Windsor appears to
>have a good torque curve from the numbers below.
> Note: 75 - 284 lb-ft @2200, 185 hp @3800, pulls to 5000 rpm
> 74 - 315 lb-ft @3100, 220 hp @4400, does not pull after 4400
>rpm.
>
> I am not biased as i have a 75. Of course it has not seen the road
>in over 10 years.
>
> Jamie
>
>* Jamie Olenick olenick@ssims.nci.nih.gov
>* "I'd rather be rich than stupid" J.H.
>
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