flamin-roids

I just recently replaced my auto in my '89 GXL with a S4 TII transmission. The trans was mounted and fitted successfully and the car runs superb. I also included a racing flywheel in the mix. Now my car is somewhat quicker but I was pondering as to if any of the leftover auto crap is holding me back. Like for example I still have the 3.90 rear end and even though my car is running smooth and produces more power it seems like something is holding it back. Would a transisition to a 4.10 TII rear or even a 4.30 GTUs make a significant difference? I was told my final drive is too tall and its hurting my acceleration.

Kenteth

the rear end won't produce more power.

a 3.90 --> 4.10 will make 5% difference...
a 3.90 --> 4.30 will make a 10% difference
a 3.90 --> 4.60 will make a 25% difference

Note that difference does NOT mean better or more powerful, it just plainly means different.

BUT.

A 390 will have better gas mileage and a higher top speed on the same engine.
A 410/430/460 will have less gas mileage, and a lower top speed on the same engine.

Its kinda like figuring where you want to waste someone. With a 390 you can hold with them until >100 when you finaly start quickly pulling away from them because they are out of powerband, and you still have plenty... *PLENTY* of powerband, or you can throw in tall gears and blow by them by the time you hit 60... BUT... by the time you hit 105, you're running out of powerband.

Personaly, i'll do anything I can get for a few extra mpg. Though I do have the parts for a 410 swap because I cracked my 390 case a few months ago

The only substantial advantage of the PITA of changing the rear end, is the fact you can drop your N/A open dif, and throw in a nice LSD. That will hold 5 times more advantage than the actual gear change will.