My take on 4.30s in the GT (long).
 

Back in early August I destroyed my stock 28 spline differential and at that point I decided to replace my gears while installing my new axles and differential. I switched over from 4.10s to 4.30s. Finally after weeks of other problems I was able to get in a handful of consistent passes down the track to prove any difference in ET's. Now my intial thoughts were that I would see an improvement roughly of .03-.05 in 60ft time which would translate into the same difference at the top end.

The passes below with 4.10s were made back in July over a span of 6 passes during two different trips. Weather conditions during my 4.10 passes were 82* and 80% humidity both nights. The weather the last two nights with 4.30s was 81* and 85-86% humidity.

Avg 4.10 4.30 Difference
60' 1.753 1.718 -.035
330' 5.303 5.282 -.021
1/8 8.284 8.268 -.016
MPH 82.06 81.64 -.42
1000' 10.866 10.858 -.008
1/4 13.057 13.046 -.011
MPH 104.04 102.96 -1.08

With 4.10s my best 60ft was a 1.66 but that was on one occassion in 60* weather and averaged very close to what is listed above. Since going to 4.30s I've stayed very consistantly at low 1.7's with a best of 1.691 tonight. So in my opinion unless you damage your gears or have to replace your gears otherwise you won't see that much of a gain in ET's. I think once the weather drops a little more I'll see a little more improvement but for the most part I picked up about 3 hundreths or so in my 60 foot times. I'm not to concerned with my loss in MPH, since some of that is due to the gears the rest I figure it from the worse humidty and my one blown out muffler.

My personal opinion is that the car feels like it is leaving much harder off the line versus the 4.10s and the 1-2 comes very quick and it even pulls both wheels now (got video footage http://www.mustangworks.com/msgboard/biggrin.gif). I do go through the traps at 5800 for those of you that asked before I actually paid attention the last two nights. Gas mileage is identical to 4.10s, right around 18-19 MPG normal driving and 25-27 on long trips (over 200 miles) @75MPH. Anyways that's my take on 4.30s.

Bill

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00 GT, MAC Offroad H, Steeda Pulleys & Timing Adjuster, C&L 80mm, 4.30’s, Flows w/turndowns, UPR shifter, UPR Pro Series LCA’s, Lakewood 70/30’s & 50/50’s, 253.8 RWHP/292.8RWTQ
Best ET 12.91
Best MPH 105.49
M/M 100, 7085
2001 Mod Motor Shootout 2V NA Champion

Mustang92 how much of a difference should I see when I change out my 3.73 for a set of 4.30?

Will

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98Cobra-3.73,Offroad
Xpipe,Flowmasters,Mac Cold air,SteedaTiming Adjuster16deg,Autometer Shiftlight,NittoDragRadials
60ft-2.013 1/8-8.488 mph-85.170 1/4-13.123 mph-106.148

Assuming your using street tires I wouldn't expect much of an improvement. If you step up to DR's I'd say you would knock off roughly .1 - .15 in your 60 foot times. Then changing to 4.30s I'd think you would pick up about .15 - .25 in your ET's.

Bill

Interesting and excellent comparison
I always enjoy reading stuff like this.

Skyler

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-1989 Saleen Mustang #406-
TFS TW Heads, E-303, Edelbrock intake, 70mm TB, 73mm MAF, 24lb injectors, 1 5/8 shorties, Off Road H, 3 Chamber flows, Jaz Race seats, Back seat removed, sub-frames, Roll Cage, and a 80 shot of N20.
12.54@107.4 Motor
332RWHP, 350rwtq