Okay here's the dilly, I have a 91 gxl and 90 gtu, the gxl is my driver, I just use the gtu for parts. K here's the question, the gtu is an a/t and the gxl is a m/t. I was told the diff on the gtu with the a/t has a better ratio. Of course I'll be switching down the road to a lsd but I figured in the mean time since I have the other diff would it be worth swapping or is this a bunch of BS?

 

your autobox gtu will have a 390 final, the gxl probably has a 410 (maybe a 430, but i doubt it).

I swapped out my 390 for a 410... You accellerate SLIGHTLY (by the means of barely noticeable) faster, and lose about 2-3 mpg. If you're gas conscious or are broke/student, keep your money and stay with the 390 for the better mpg.

Its not a dificult swap if you have the right tools and your car isn't a rust bucket. I personaly wouldn't have swapped it out unless the 390 had a cracked case (it was cracked) or I hd an lsd to install (sigh, someday).

 

that's cool, thanks for the info, I have to drop the trans this weekend and put in a new clutch, maybe I'll go ahead and switch to the 390 while I'm under there.

 

... i wouldn't change frmo 410 to 390..., you'll get a few extra mpg... but you'll lose acceleration...?