Thread: Gear ratio & tunes?
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Old Wed, October 14th, 2009, 07:57 PM
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Jackpine Jackpine is offline
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Originally Posted by cleatus12r View Post
It's not correct, Jack. With the 95-97 trucks, the data given in the tuning software shows a 64:1 final drive ratio and a 65535 rev/mile. Why? I don't know but it has little to no effect on the operation of the vehicle even when correct numbers are given like 4.10:1 or 635 rev/mile. I don't think that the PCM in those trucks use that particular value when figuring shift points. The automatic-equipped Super Duty trucks are sensitive to those values though.
OK, I've got it now! It's really just the largest signed integer the processor can store: 2 ^ 16 -1. (I knew the number was familiar to me from somewhere). The processor is a 16-bit machine and for some reason, it's holding a hex value of 7FFF - "maxint", in that position). Doesn't look like it serves any useful purpose at all though. Wonder if the good Doctor knows anything about it?

- Jack
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