[Super73]

I drive a 30" tire with 4.56's on the street on a regular basis. The lock up verter helps a ton with my loose 4,500 stall. A stock stall would show a smaller drop in RPM by engaging the lock up. I see 2,475 rpm at 65mph. Remember, the 80E's has a tall first. A steeper rear gear makes things nice.

My wife's trailblazer SS has a factory 4.10 gear and a 29" tire from the factory. It cruises at 2,300 at 65mph. I use the wifes TBSS to tow the race truck to the track (3600lbs + 1500lbs = 5100lbs + gear)

If I was rocking a 31.5" tire (which is what a 305/40/22 comes out to) I'd probably opt for a 4.30.. This would put you at 2,250 rpm. Or a 4.56 would put you at 2,375.


Your not really going to loose a ton of mileage as your still keeping the motor in a very efficient range. If anything, you might actually pick up a little since your putting such a tall tire on it with such a tall gear and no longer lugging it.


BTW, a 3.08 with the tire you want to run would put you at 1,600 rpm..