From 4.11's to 2.80 gears...track results
 

In my rx7 I hurt the 3rd member so I took out the 4.11's and put in some 2.80 gears as a quick fix for now until I can get 3.55's in it. I also should mention I'm running a 315/60/15 mt drag radial, so a 30" tire, an a th400 with a 8" coan nitrous converter(about 3600rpm in my light car, was a 4000 in my firebird). These gears make the car drive nice, 2300rpms at 75mph. Also on the street the car LOVES these gears, leave on motor and spray 30ft out no spinning!

Before/after results...

Motor passes...

60ft.. before 1.480....after 1.589
1/8th before 6.843....after 7.028
mph.. before 100.22....after 98.38
1/4... before 10.765....after 11.021
mph.. before 125.45....after 123.03

Before:
http://www.youtube.com/watch?v=NAh6asKK4hE

After:
http://www.youtube.com/watch?v=SVSiqtkN-ZI

Only difference is the gear and in 1st I'm spinning it only to 6000 or so vs before 6500. With the new gear it goes through traps around 6500rpm in 2nd, before around 6400rpm in 3rd.

100 shot passes...

60ft.. before 1.470....after 1.606
1/8th before 6.544....after 6.665
mph.. before 105.43....after 106.39
1/4... before 10.287....after 10.366
mph.. before 129.34....after 131.86

Before:
http://www.youtube.com/watch?v=kn8gLXw7ahQ

After:
http://www.youtube.com/watch?v=0z8BGbNWYs4

I was spraying around 60ft out on both these passes. Before with the 4.11's I was running out of gear, I'd quit spraying it around 6200rpm and run it out the back down on motor up to 6700-6800rpm. With the new gear I shift to 3rd so I don't run out of gear, although that 3rd gear change not far from the traps probably isn't helping me. Also the new passes with the nitrous I wasn't spraying through the shifts like I did before. The car has done 131.98 with the 4.11's on another pass when I spun and quit spraying at 6200rpm and went through traps at 6900-7000.

I'll try to hit the track again Friday to see if spraying out the gate will get me a 1.4x 60ft again. Just thought it was interesting, took out A LOT of gear and lost a tenth in the 60ft on motor and 2.5 tenths on the back end and 2.5mph(didn't expect to lose the mph)

Interesting info. Did you record the weather conditions?

Same weather conditions, I didn't get the exact DA though, should've been floating around 2000 both times.

This is cool info. A lot of the turo guys LOVE 2.75 gears in their axles if they don't have an OD trans. Sounds fun.

dude sick Rx-7!!!! I had a 1985 as my first car, then i bought my 99 z28 BIG DIFFERANCE...lol

Man i wish i still had the Rx-7 tho.:( it was bone stock from my late uncle when he gave it to me, i didnt know anything and was stupid, i drove it for awhile then it had a loss of power and I didnt know how to work on it and sold it for $800...it was perfect too.... the guy who bought it made it a drag car to with a 13b swap....saw it years later and almost cried damn was i dumb