Hi gang,
Still pondering my rear end gear change. I know I'll get the low RPM cruise
at highway speeds, but having trouble figuring what I'm going to give up on
off the line quickness. I'm using a web gear ratio calculator and trying to
figure out what speeds I'll get in the different gears.
I've looked but couldn't find TR8 gear ratios on the web. From the speed I
get in different gears at 4 K RPM, using 4th gear as 1.0, and a roughly 10 %
speedo error, I'm getting ratios of 3.0, 2.0, 1.4, 1.0, and 0.83 (seems like
I've looked up and knew 3rd, 4th, and 5th before). Can somebody confirm those.
Another funny thing using the ratio calculator - I have to put smaller
diameter tires into the calculator to match the gears / RPM / speed. My
195/50/15s calculate to 22.68" in diameter, but I have to put in 21.75" to
match the
speed. I've measured the tire diameter with a ruler and get 22.25" but it's
in the dark garage, and might be a bit innacurate. Anybody see something I'm
doing wrong.
Then the big question. When I change the rear end gear ratio to 3.0, I
obviously get higher speeds in all gears at the same RPM. So what will that
do
to my acceleration. These 3.5 engines have good low end torque, and I've seen
many of you going with low rear end gear ratios, but can somebody give me
the theory of off the line quickness vs top end speed and how to come to the
right balance. The original 3.9 rear end in the MGB was important for a low
HP
/ torque engine to get up to speed more quickly because it gets the engine
in to the better power range in each gear more quickly, but dragsters use the
short (is that right), higher rear end ratios to accelerate more quickly. My
instinct is that the 200 or so HP and good low end torque of the 3.5 engine
give the MGB a good blend of off the line acceleration as well as top end
with the TR8 transmission and a 3.0 rear end. Does anybody have more
specifics?
Safety Faster...with a V8,
Rick
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