Quick Change Ratios Chart Not Accurate?

[ratracer49]

Maybe I'm overlooking something here but I'm finding numbers that don't match up to my math on Winters Quick-Change chart. Take for example.

Gear set 41 is as (17/28) gear set and for a 4.12 R&P (8-33 teeth) the chart lists the final high gear ratio as 6.81.

Now if I calculate the ratio I get 28/17*33/8 = 6.7941.

Even if I use the charts rounded numbers of 1.647 for the gear set and 4.12 for the R&P I get 1.647*4.12 = 6.7856.

Neither one get me to the 6.81 ratio on the chart.

I find this throughout the chart. Is there something I'm missing here? Is there some other factor I'm overlooking?

https://wintersperformance.com/applicat ... ressed.pdf

[ratracer49]

If anyone running a quick change rear end that is willing to try this app out and give me some feed back I'd appreciate it. It's a free app and currently calculates final ratio and selects the new gear set you need to change to a desired RPM. Also are there any other gearing calculations that you think would be nice to have that I might add?

https://play.google.com/store/apps/deta ... Calculator