Hey guys, long time reader turned poster, and Im not sure this is the right section but I have some questions about my intended drivetrain setup for my project so i figured id post it here. Im working on my build slowly but surely as im on a college student budget. My plan is to mate the 1.6 ive been building to a newer 6 spd tranny to a 3.9 torsen. I have a 92 1.6 with the vlsd. My questions are as follows:
1. Is a direct bolt in swap using this combination possible using already existing mounts/ not needing a longer or shorter driveshaft? (Is the 6 speed tranny the same length as the five speed?)
2. Would 3.9 be the best gearing for the 6spd? (I currently dd the car but plan on tracking the car in the near future and putting down abt 250rwhp) (and i would really not want to spend the money on the corksport 3.63s)

 

What happened to the 1.8 that came with the 6 speed? The six speed is a direct swap, but you will need a 94+ driveshaft and axels for your diff swap. Brain has more information in a sticky in the build threads section.

 

94+ axles won't work, you need '99+ axles, they're different between torsen 1 and torsen 2.

What you're proposing is really quite silly TBH. You'd be better off to sell the 6 speed and 3.9 and use a 5 speed and 4.1, then put the extra money into the car in other places. You don't need the 6 speed for 250 HP. Either that or get the 1.8 to go along with it.

As for the actual answer to your question, mounts should be a yes, but I believe you'll need the driveshaft to go match if I'm not mistaken.

 

Cost issues aside which would have better gas mileage? 4.1 with a 5 spd or 3.9 with 6spd?

 

For one, how can you put cost issues aside when discussing gas mileage? That itself is a cost issue.

But they would be virtually identical on the highway. The 5 speed has a taller top gear than the 6 speed which almost makes the difference between the 3.9 and the 4.1. The 6 speed/3.9 combo lets the engine spin 40 rpm slower at 65 mph.

http://www.flyinmiata.com/tech/gearing.php

 

thank you turbofan. im going to go with a 4.1 and 5 speed from a 96 i found for a steal.