Change gearbox gear ratio

JayJay said:
In an attempt to answer my own question, I did some calculating of the final transmission ratios with standard and Mitchell transmissions, and with/without Mitchell overdrive. Interesting - see attached.

It appears that with standard transmission and Mitchell O/D, the jumps from 2 to 2 O/D to 3 to 3 O/D are about the same - a gear reduction of 26-27% (I'd guess that might be part of why the 26% O/D ratio was selected). The jump from 2-3 without the 2 O/D in between is substantial - a gear reduction of 46% (this is the 2-3 gap we're all familiar with and that Y-B alludes to above).

With the Mitchell transmission first and second gears at 15% higher, the jump between 2 O/D and 3 narrows considerably, about half. But you get that back in a reduction between 2 and 3, the jump is about 28% less.

So with a Mitchell transmission you get a narrowing of the 2-3 jump coupled with synchromesh 2 and 3. You "pay" for that with a narrowing of the 2 O/D to 3 gap. Overall top end remains unchanged.

Have fun. Now back to our normally scheduled programming.


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Click to expand...

I think you have to much time on your hands... :p :p
 
Y-Blockhead said:
I think you have to much time on your hands... :p :p
Click to expand...
Why be productive when you can waste time doing mostly useless stuff? Back in the early '70s my college roomie obtained one of the first hand held calculators - a Texas Instruments TI-50, as I recall. We spend a good part of a rather beer-lubricated afternoon around the swimming pool calculating how many Big Macs, laid side to side, it would take to go from San Francisco to St. Louis, MO. We were quite proud of ourselves.
 
At any rate, the Mitchel Synchro Trans make shifting sweet even without the O/D. The O/D just puts the icing on the cake.

Yesterday while out on a small tour, guys with lighter cars had a hard time staying with my Town Sedan from a stop because I had 5 useful gears with the Mitchell Trans/Mitchell O/D combo to keep the engine in the power band.

But, but officer! We weren't "street racing" a 95 year old car. Honest!! :rolleyes: :rolleyes:
 
In the early automotive history it was considered the mark of a good car that could use high gear from 5 mph to 100 mph. The Model T is a good example of this idea, although it would go nowhere near 100. First gear was just to get the car started and then it went into high that was good from 5 mph to top speed of about 45. The modern thinking is quite different.
 
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