TwinTurbo.NET: Nissan 300ZX forum - 6-speed transmission: gear ratio study
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Subject 6-speed transmission: gear ratio study
     
Posted by Technomancer on October 27, 2004 at 12:56 PM
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Message After seeing the post about somebody putting a 350Z 6-speed transmission into a twin turbo I did a few calculations. I wanted to see what happened to the final gear ratios and thus what would happen to the shift points. Below is the html version of my spreadsheet, assuming the standard trans and rear diff, plus several variations. Sorry if something is scrambled...at top right is the 350Z configuration and I had it in a green color so I would know it was not with the others...html conversion puked here.

The first variation is with or without the NA differential. One thing to notice is that contrary to the earlier statement, the new 6th gear is not the same as the old 5th gear.

The rest of the variations are me putting in a hypothetical final drive ratio to get different shift points for the resulting car. I have just assumed a starting top speed, RPM limited, at 180 mph. Close enough. The top speed for other configurations just scales with the total gearing ratio for the top gear.

This was all just playing around. If somebody wants the spreadsheet, shoot me an email. Look, I have no interest in seeing a repeat of the "350Z trans is weaker, why would you do that" brigade. I'm sure you're right, but that's not the point of this post, and I'm not putting a 6-speed in my car thanks.

So you know, my personal favorite (of these I'm showing here) is where the old 5th gear = new 5th gear and there is now a 6th gear "double overdrive". The lower gears are all taller than they were, but if you have power mods you probably like that more anyway.












[if supportMisalignedColumns] [endif]
Gear number Gear ratio Final Drive Total gearing 350Z 6-speed
300ZX 300ZXTT with NA diff 1.000 3.794 3.538 13.423
1 3.214 3.369 10.828 4.080 13.113 2.000 2.324 3.538 8.222
2 1.925 3.369 6.485 4.080 7.854 3.000 1.624 3.538 5.746
3 1.302 3.369 4.386 4.080 5.312 4.000 1.271 3.538 4.497
4 1.000 3.369 3.369 4.080 4.080 5.000 1.000 3.538 3.538
5 0.752 3.369 2.533 4.080 3.068 6.000 0.794 3.538 2.809
top.speed 180 mph top.speed 149 mph
custom differential 1 custom differential 2 custom differential 3
300ZX with the 350Z 6-speed with NA diff old 5th gear = new 6th gear old 5th gear = new 5th gear old 4th gear = new 4th gear
1 3.794 3.369 12.782 4.080 15.480 3.190 12.103 2.533 9.610 2.651 10.058
2 2.324 3.369 7.830 4.080 9.482 3.190 7.414 2.533 5.887 2.651 6.161
3 1.624 3.369 5.471 4.080 6.626 3.190 5.181 2.533 4.114 2.651 4.305
4 1.271 3.369 4.282 4.080 5.186 3.190 4.054 2.533 3.219 2.651 3.369
5 1.000 3.369 3.369 4.080 4.080 3.190 3.190 2.533 2.533 2.651 2.651
6 0.794 3.369 2.675 4.080 3.240 3.190 2.533 2.533 2.011 2.651 2.105
top.speed 170 mph top.speed 141 mph top.speed 180 mph top.speed 227 mph top.speed 217 mph


- John


     
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