[tdangle]

Originally Posted by rpmerf

My suburban is a 97 - overdrive with lockup. I can plug it into a calculator and see 34.7 MPH per 1000 RPM.

To get ~35 MPH / 1000 RPM with a 0.7:1 gear ratio and a 4.10 rear, you would need to have ~33.5" tires.

I'm assuming you have 235/85R16, as that's what came on my 70 C20. They are 31.7". With OD and a 4.10 rear that should give 32.9 MPH / 1000 RPM. You should be closer to 2,125 RPM at 70 MPH.

Here is a calculator to get the speed at a given tire size, trans ratio, rear ratio, and RPM.
https://spicerparts.com/calculators/...rpm-calculator

Sounds about right. didn't realize you were comparing to a different vehicle than in your signature. And yes I have 265-75-16 with a dia of about 31.6" so just over 2K is correct. Way nicer than when I had the TH350 trans.