I remember seeing a chart posted here I think. It had a different data of different rpm scenarios for different gear combos. Like what the rpm's were in each gear and for different ratios. Anyone know what I'm talkin' about?
It changes with rear tire height Bernie -- so you have to be careful about what you're looking at. Also, unless tachs and speedos are accurate (they rarely are), the numbers calculated may not match up to what you're seeing on gauges. I prefer to simply calculate the rpm for each specific incidence.
Give me your rear tire height, rear gear ratio and tranny ratios and I'll show you how to do the calcs. Then you can play with different tire sizes, rear gear ratios or tranny ratios and see the impact on rpm relative to road speeds.
You're best bet would probably be to dig into excel and build your own calculator. The formulas are pretty simple math, so in a few hours at most you could have your own customizable, graphing calculator. By making your own spreadsheet you have control over how all the variables are used.
If you want I might be able to email one that I have, but I am not sure if I can extract it from excel. PM me if interested and I will give it a try.
I have a graph showing engine rpm vs vehicle speed for 4 combinations. I used 2 different trans ratios and 2 different gear ratios. I also worked in swapping just fifth gear on one of the combos. WOT shift points can be seen, as well as theoretical top speed (not accounting for aero/rolling drag).
I then worked another graph to show just fifth gear of each combo under cruising conditions, so I could get a feel for fuel economy differences.
I probably spent more time formatting than setting up the equations.
If you just want to know the difference in top speed for a given ratio, it would not take nearly as long. Also, I am still learning excel, so I tend to work a little slower.