Quote:
Originally Posted by roadrod2000
I have a HIPO 289 powered Unique FIA car with a 4.27 rear axle ratio and a ford motorsports T5. The camshaft is a solid lifter with .560/.512 I/E lift and 244/254 duration at .050. I just looked at a chart comparing RPMs at MPH for both my setup and the one proposed by XB-60 /Glen (3.07 rear and wide ratio toploader). What I find is that my 2nd, 3rd, and 4th gear are very close to the same (compounded ratio) as Glen’s 1st, 2nd, and 3rd , with that in mind this is what I experience driving the car; 1st gear is too low, I can easily get the car moving by starting in 2nd (starts on a hill might be a challenge though ) 2nd through 4th are well spaced and fun, but my jump from 4th to 5th is too much of an RPM drop, at 55 in 4th I’m at about 3000 rpm’s, the shift to 5th drops me to about 1900 and the engine is not happy there, so driving a winding mountain road is a battle between 4th and 5th . On the freeway at 70 I’m at 2400 rpm’s and that works fine for cruising but ideally I want to raise the rear ratio and drop the overdrive ratio so that 4th to 5th is closer. To summarize; the 3.07 /wide ratio toploader combo would probably work well with my car and for how I drive it, but on that hill I would want a slightly lower 1st.
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Good, thanks, I haven't had many (good) comments on my proposed gearing. It sounds like your 5th gear is a 0.62 overdrive, so your fourth - fifth split of 1.56 is a little different to my third - fourth split of 1.36
Having a high first gear - equivalent to your second gear - is OK, and even desirable. On both of my current cars I often start off in second gear if it's not uphill, and one of the cars, 35 years old, still has the clutch that it drove out of the factory with, so I'm easy enough on clutches even taking into account the second gear starts.
Cheers,
Glen