6 Speed vs 5 Speed with Boost and Stock Internals
 

I have an NB1 with a 5 speed and around 77k on it that I will be turbo-ing soon and I am planning to stick with stock internals. A year or two ago, I pickup up a 6 speed out of a wrecked '01 with about 140k on it with the intention of putting it in and changing my diff to 3.9 or 3.6 rear gearing. Im not feeling too keen on spending the extra time and money on the rear end any more, but with boost incoming, I was wondering if there would be any added value to running the 6 speed instead of the 5 speed.

I know the 6 speeds are stronger, but it seems that most people are just fine running 5 speeds with boost. Also, the ~150 rpm increase with the 6 speed on the highway seems pretty negligible to me. Thoughts?

5spd + stock internals = flip a coin to see which breaks first. Probably the 5spd, but under heavy track use. Street use will likely be fine.

6spd + 4.30 rear end your car came with + boost = suck.

6spd + 3.90 + power levels limited by stock internals = fine

The stock rods are good to somewhere between 200 and 250 rwtq, which is enough to kill the 5-speed. If you've got "mechanical empathy" you can probably make the 5-speed live for a while at those power levels, but it won't be forever and the 6-speed is a worthwhile upgrade. Drag race starts will significantly shorten the 5-speed's life.

On the street I like the 3.636 with the 6-speed. Gears 1-5 are fairly close to what you had with a 5-speed on a 4.3, plus there's an extra tall 6th for the freeway. 6-speed with 3.9s is terrible at autocross, you wind up shifting between 2nd and 3rd multiple times per course.

--Ian

Oh boy, these sound like real convincing arguments for the 6 speed and spending money on the rear end. My wallet hates you guys lol.

Thanks for the quick feedback!

If it were me, i'd leave the 5spd in until/if it breaks. Then worry about the money, then.

Im getting ready to change the clutch here pretty soon, thats why I was thinking about swapping them now. The less I have to wrestle with transmissions the better, although I don't know when I would get to the rear gearing. Tough decision....

Swap trans, live with the 4.30 until you don't want to anymore, then handle that. It's not going to render the car inoperable.

+1

This.