Jeff answered it. It's to correct speedometer.
I have an Indy 426 wedge stroker w/ 515 hp and 505 torque.
I put in GV unit b/c I was redlining at 130mph and wanted to go faster.
Also my average speed at 80 mph had the engine revving to loud w/ 3 inch TTI exhaust. Since installing GV unit I also went with 245/45/17 front and 285/40/18 back. Taller tires w/ GV unit in overdrive did the trick. I hit 140 etc and car was completely stable w/ sway bars, HD 6 leaf springs, welded subframe connectors, Edelbrock IAS shocks, .960 torsion bars, firm feel stage II steering box, aluminum parts and griffin radiator w/ 2 Be cool electric fans. Car has been lowered for lower center of gravity. I had to slow down b/c I need braaaaaakes
So I'm waiting on Bear 13' rotors w/ hydrotech booster. Just placed dynomat throughout car and it's finally quiet....so now I can deal w/ 3.91 gears even though revs will go back up. 3,800 stall is too high so 9 1/2' converter will be changed to 2,500 stall
My 8 3/4 posi rear is on it's last legs so I'm thinking of changing to an updated moser or strange bulletproof unit. Car is currently stripped to metal and body work is almost done. Waiting on an AAR hood, rear and front spoiler.
Car spools up so quickly in 1st w/ foward pattern manual valve body on auto 727 that I don't have time to mess w/ 1st over. I use it after 2nd and 3rd gear. My goal is for car to be a Z06 vette, Ferrari, and porsche 911 hunter. They all know I mean business just by reading my plate....KILRCUDA
You will be so happy w/ this GV unit b/c you can cruise in OD or pound rustangs all day in 3rd