Suspension, Brakes, Drivetrain discuss the wondrous effects of boost and your miata...
Sponsored by:
Sponsored by:

6 Speed vs 5 Speed with Boost and Stock Internals

 
Old 02-13-2019, 11:22 AM
  #1  
Newb
Thread Starter
 
Join Date: Jun 2018
Posts: 40
Total Cats: 4
Default 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?
atotalpro is offline  
Old 02-13-2019, 11:34 AM
  #2  
Elite Member
iTrader: (3)
 
concealer404's Avatar
 
Join Date: Aug 2011
Posts: 10,001
Total Cats: 1,452
Default

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
concealer404 is online now  
Old 02-13-2019, 11:34 AM
  #3  
Elite Member
 
codrus's Avatar
 
Join Date: Mar 2007
Location: Santa Clara, CA
Posts: 4,412
Total Cats: 516
Default

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
codrus is offline  
Old 02-13-2019, 11:42 AM
  #4  
Newb
Thread Starter
 
Join Date: Jun 2018
Posts: 40
Total Cats: 4
Default

Originally Posted by concealer404 View Post
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
Originally Posted by codrus View Post
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!
atotalpro is offline  
Old 02-13-2019, 11:45 AM
  #5  
Elite Member
iTrader: (3)
 
concealer404's Avatar
 
Join Date: Aug 2011
Posts: 10,001
Total Cats: 1,452
Default

If it were me, i'd leave the 5spd in until/if it breaks. Then worry about the money, then.
concealer404 is online now  
Old 02-13-2019, 12:03 PM
  #6  
Newb
Thread Starter
 
Join Date: Jun 2018
Posts: 40
Total Cats: 4
Default

Originally Posted by concealer404 View Post
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....
atotalpro is offline  
Old 02-13-2019, 12:07 PM
  #7  
Elite Member
iTrader: (3)
 
concealer404's Avatar
 
Join Date: Aug 2011
Posts: 10,001
Total Cats: 1,452
Default

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.
concealer404 is online now  
Old 02-13-2019, 12:58 PM
  #8  
Supporting Vendor
iTrader: (31)
 
Savington's Avatar
 
Join Date: Nov 2006
Location: Sunnyvale, CA
Posts: 15,094
Total Cats: 1,876
Default

Originally Posted by concealer404 View Post
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
__________________
Trackspeed Engineering
High-Performance Turbo Specialists - Sunnyvale, CA - 650-701-7223 - Email us!
Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
Savington is offline  
Old 02-13-2019, 04:21 PM
  #9  
mkturbo.com
iTrader: (24)
 
shuiend's Avatar
 
Join Date: May 2006
Location: Charleston SC
Posts: 14,295
Total Cats: 1,293
Default

Originally Posted by concealer404 View Post
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.
This.
shuiend is offline  
 
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
ak47bravo
DIY Turbo Discussion
43
12-28-2018 09:28 AM
90 Turbo
Engine Performance
40
11-04-2011 04:09 AM
Turbo_4
Insert BS here
13
02-22-2010 10:38 PM
1967cutlass
DIY Turbo Discussion
5
12-19-2007 06:57 PM
mtncrvr
Methanol/Water Injection
3
10-11-2007 09:25 PM


Thread Tools
Search this Thread
Quick Reply: 6 Speed vs 5 Speed with Boost and Stock Internals


Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.