Tony,
I'll try to get to the point of your question with a minimum of math. To get
the equivalent of 2.88 gears in 0.8 5th gear is 2.88/0.8 = 3.6. The closest
stock gears to this would be 3.54's. So, if you put 3.54's in, you will now
have five gears, and fifth gear will be virtually identical to your
toploader's 4th gear. Then there is the much more subjective question of
whether you want this fairly tall final gear ratio. There has been much
discussion on that subject lately and it depends on whether you want the car
for high speed freeway driving at the one extreme, or for autocrossing at
the other. If you like an even taller final ratio, then maybe 3.31's would
be good. I know that some even stick with 2.88's, but that puts the rpm's
really low and if you have any kind of cam in your engine, it's not going to
like it and, of course, you will have less throttle response. So, for mainly
highway use I would recommend 3.54's or 3.31's, but nothing lower. If you
want to maximize autocrossing or drag strip performance, then a rear end
ratios around 3.97 is what you need. (See my article on the Tigers United
Website for more details.)
Getting back to your other four gears, there is an important question of how
these compare to your four speed. Let's keep it as simple as possible and
only consider actual numbers for first gear, bearing in mind that the closer
the gear ratio difference between first and fifth, the better overall
acceleration you will get. This fact is alluded to in Ron Fraser's
statement: "This is about 10% reduction from stock gears and will give you
better acceleration in all gears." This probably could have been stated more
accurately as "will give you better overall acceleration throughout your
shift range". In any one gear, it doesn't matter where the gearing is, in
the transmission or the rear end. But, as you accelerate and shift, with
closer ratio gears you can keep the engine running closer to its optimum
rpm's, thereby improving your overall acceleration.
That said, let's compare gear ratio ranges for the four and five speed. The
toploader uses 2.32 and 2.78 first gears in the close ratio and wide ratio,
respectively. I don't know what first gear ratio you are going to get in
your five speed, but I'm pretty sure it's even lower (higher numerically)
than a wide ratio toploader. I see first gear ratios for T-5's of 2.95,
3.35, 3.5, and 3.97. Assuming you get the lowest of these, the 2.95, it is
going to pull stumps with say a 3.54 rear end compared with even a wide
ratio and 2.88's. I strongly recommend for a relatively light car like a
Tiger, and for performance reasons, get the highest (lowest numerically)
available first gear in your five speed. I assume that's what Dale would
give you anyway, but ask to make sure.
Bob
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