[Schrade]

Originally Posted by ZRXMAX

If you look at the speed in each gear you will see that tallers gears add mph at the shift points as compared to shorter gears.

Here are the numbers for 3.07 compared to 4.10s
7000 rpm and 25.5 inch tall tire with ZF-6 ratios from Procrastination Racing's website.

http://www.angelfire.com/fl/procrastination/rear.html

3.07 1st 65.5 mph
4.10 1st 49.07 16.43 mph difference

3.07 2nd 97.17mph
4.10 2nd 72.76 24.91 mph difference

3.07 3rd 133.05
4.10 3rd 99.63 33.42 mph difference

3.07 4th 172.97
4.10 4th 129.05 43.92 mph difference

You are correct... the difference is "time" spent in each gear to gain those additional mph between shifts. The starting rpm at each shift is right around 4720 rpm.

However... It sure does seem like the rpm drop is increased with 3.07s

My speedometer calibration was off almost exactly 25% when switching from 4.10s to 3.07s. I made up a paper speedometer reference sheet for ORRing so I could look at the speedo and then look at my reference sheet.

I bought a Dakota Digital box years ago that was designed to allow me to calibrate my speedometer regardless of what gears I as using. I never could get it to alter the signal to the ECM to give me the correct speed. Has anybody here ever tried one of those boxes ?

I had one installed in my automatic conversion. SGI-5 C

Worked properly at speed, but at '0' MPH, it gave an erratic reading, for which there was a troubleshoot symptom. Followed it to a 'T', and didn't solve the problem.

Ended up removing it, and using the Tranny Control Module for speed signal feed.

Solved it. Sold the DD on eBay, guy had no problems with it on his project wheels...

http://www.zr1.net/forum/showthread.php?t=19299