Drivetrain Upgrade (clutch, trans, LSD, etc)

[blodi]

Looking to upgrade the drivetrain on my 71 240Z this year. I want to change out the clutch, flywheel, trans, and diff.

 

My current setup:

Engine: L28,  500/300 cam, high compression, triple Weber's,  etc.....last made ~200rwhp on dyno. 

Clutch/Flywheel: Stock spec Exedy clutch/Stock Flywheel

Trans: Nissan Comp (steel syncro) wide ratio 280Z trans-standard 280z ratios :

32010-N3030 3.321 2.077 1.308 1.000 0.864 (wide ratio)

Diff:  3.54 open diff (car was originally an auto, thus the 3.54)

 

Goals: A bit better throttle response, clutch that holds the power a bit better, closer ratio trans , a bit less RPM at highway speeds, LSD. 

 

Current thoughts for new setup:

Flywheel: I don't want to lose the drivability too much due to the big cam and this is purely a street car, so this mildly lightened wheel intrigues me:

https://www.californiadatsun.com/flywheel/lightened-resurfaced-balanced-steel-non-turbo-225mm-flywheel.html

 

Clutch:

Exedy Stage I, would this sufficiently hold my power? Current, stock spec clutch will slip every once in a while if quickly shifting under full throttle/ high rpm from 2nd to 3rd.  Just need a bit more grab. Again, want to keep street drivability. I have a really heavy clutch in one of my other cars and don't want to go there. 

https://www.lmperformance.com/855771/06805a-exedy-stage-1-organic-clutch-kit-nissan-280z-l6-28-2-seater.html

 

Trans:

280zx close ratio seems to fit the bill.  Does the 280z clutch and flywheel work with that trans or do I need a 280ZX clutch/flywheel?

 

Rear diff:

Looking at doing the Subaru STi R180 diff. Seems most like the 3.90 ratio with the close ratio trans? I know that I need the adapter hubs as well. 

https://zcardepot.com/products/subaru-r180-swap-billet-axle-set-240z-510?gclid=Cj0KCQiAraSPBhDuARIsAM3Js4q5CMnPC5DVgwnf0LwZQbsZMsb389huRDMDK9EjWpTrE1ZuekVpV-kaApynEALw_wcB&utm_campaign=google shopping&utm_medium=cpc&utm_source=google&variant=39589764792433

 

It looks like that trans/ diff combo would make 1-4 shorter and closer ratios than my current setup and 5th would be a tad taller?

I know there are hundreds of threads on this stuff, but some are 10+ years old at this point and just want to make sure what I'm doing here makes sense before I start sourcing and buying up parts. 

Any thoughts or other suggestions are welcome. Or if you have parts i might need or might be interested in any of my old parts, let me know. Might be a few months here though til I am ready to swap it all. 

Anything else I'm missing that I would need to swap?

 

Thanks! 

 

 

 

 

 

[heyitsrama]

You'll be up there in the RPM at `highway` speed, whatever that is in your area... I usually drive the car at 70mph street and highway.

I've had a hard time finding a STI r180, consider that most if not all of them are will be used, and probably need a rebuild.

I started sourcing r200 diffs personally, but finding the pinion ring at 3.7/3.9 can be a challenge, mfactory // EBAY LSD seems like good alternatives.

The gearbox should mate up and fit, for the flywheel I like the `fidanza` brand, i went with a zx turbo clutch which was larger, but retains a stock feel when mated to a light flywheel, its comfortable.

the close ratio gearbox might be hard to source, you can also look at finding a 240sx gearbox and getting the bellhousing modified. Or a cd009 w/ modified bellhousing....

 

The lack of rear ends kinda sucks... almost feel like doing the work to put a ford 8.8 in the rear, more selection, cheaper price.

[blodi]

So currently, I am seeing about 3500rpm at 70 and 4000rpm at 80.  Now that said, I don't know how accurate that is.  I know I  have a 3.54 rear end. As I said, car was originally auto and I have checked it several times (lifted one rear wheel, turned it around twice and counted the input shaft revelations at just over 3 1/2.)

But, I found out that I have a white (3.90) speedo gear in my trans. I installed a correct black 3.54 gear and the speedo was obviously reading way too high.   So someone must have figured out the speedo was reading wrong at some point and put in the white gear to get it closer. 

Would I be better off staying with a 3.54 or maybe splitting the difference with a 3.70? I do a fair amount of driving with it on the freeway and wouldn't mind less RPM. And I'm not hurting for punch in lower gears...1st just spins the tires. 

Thanks for the tip on the larger clutch/flywheel. Could I run a stock spec clutch with the larger setup and be able to hold my power sufficiently?  Ironically, when I bought my trans it came with a Fidanza flywheel that I sold off because I thought I was keeping the stock L24 at that point. 

 

 

[Zed Head]

4 hours ago, blodi said:

Trans: Nissan Comp (steel syncro) wide ratio 280Z trans-standard 280z ratios :

 

1 hour ago, blodi said:

But, I found out that I have a white (3.90) speedo gear in my trans. I installed a correct black 3.54 gear and the speedo was obviously reading way too high.

I don't think that you really know what your ratios are.  No offense.  Unless you have tiny wheels.  The black gear is the 3.54 gear so should give the correct speedo reading.

I don't know that the "Nissan comp steel synchros" has standard 280Z ratios either.  The ratios you wrote look 280Z but I don't know that there is a "Nissan comp" 5 speed like that.  What would be the point?  No offense, the numbers just don't fit together.

You said you'd like a bit less RPM at highway speed but then said a 3.9 diff might be good.  That's going the other way if you really do have a 3.54 now.

Also, general warning, beware of California Datsun purchases.  His track record is poor.

[blodi]

27 minutes ago, Zed Head said:

 

I don't think that you really know what your ratios are.  No offense.  Unless you have tiny wheels.  The black gear is the 3.54 gear so should give the correct speedo reading.

I don't know that the "Nissan comp steel synchros" has standard 280Z ratios either.  The ratios you wrote look 280Z but I don't know that there is a "Nissan comp" 5 speed like that.  What would be the point?  No offense, the numbers just don't fit together.

You said you'd like a bit less RPM at highway speed but then said a 3.9 diff might be good.  That's going the other way if you really do have a 3.54 now.

Also, general warning, beware of California Datsun purchases.  His track record is poor.

I know the black gear should be correct, that's why it's confusing me. I've checked the rotation ratio several times on the diff thinking something must be off.  3.54 was the stock diff in auto cars, obviously it could have been changed, but the number of rotations always comes out the same.  Maybe I need to pop the rear cover and have a look. Even before I changed from the auto the manual, it had the white gear in it. 

There are 6 different Comp transmissions (see below), mine is supposed to be the one with the stock 280z ratios. I had the trans rebuilt a few years ago and the rebuilder was the one who figured out it wasn't a standard trans due to the synchros and also calculated each of the ratios out for me so I'd know which version I have once we figured out what it was.  Looking at an online calculator though, with a 3.54....4K at 80 would be a 1:1 ratio in 5th....so maybe the rebuilder was wrong on the ratios? He told me it was an overdrive trans. Hard to tell now with the trans in the car, but maybe I can mark it and rotate the engine manually to see.  The plot thickens I guess. It would explain the high RPM at speed.   Still doesn't explain the wrong speedo gear working out to the right speed. I guess I have some homework to do to figure out what I'm really starting with here. 

 

Factory Competition Transmissions 77 - 83
There were Factory Competition 5-Speeds available through NISSAN Competiton Dept. There were two overdrive Transmissions, and four with the direct drive (1:1 in fifth gear)

                #1       #2       #3       #4       #5      

32010-N3130   2.906    1.902    1.308    1.000    0.864  (close ratio)

32010-N3030   3.321    2.077    1.308    1.000    0.864  (wide ratio)



32010-N3220   2.818    1.973    1.470    1.192    1.000

32010-N3221   2.348    1.601    1.296    1.138    1.000

32010-N3222   2.192    1.601    1.470    1.138    1.000

32010_N3201   3.321    2.270    1.601    1.240    1.000   (rally transmissions)

 

 

 

[blodi]

OK, I went back and found a post from 6 years ago when I had the trans rebuilt...here is what the trans guy told me:

1st- 33 Main 19 Counter=2.357

2nd- 28 Main 19 Counter=1.473

3rd- 26 Main 28 Counter=.928

4th- 22 Main 31 Counter=.710

5th- 19 Main 31 Counter=.613

 

His  math on 1st gear was wrong and should be 1.736 if those tooth counts are correct.  If you assume 4th is 1:1 and divide 1/.710 you get 1.408.  Take that times the numbers above and you get the wide ratio gears....other than first. So that one is a mystery still. Maybe I'm calculating this wrong? What if you assume 5th is 1:1? 

 

[heyitsrama]

@blodi pulling the rear cover off can be a pain in the arse because of the mustache bar. You could do this:

1. Calculate the diff ratio by spinning the wheels see https://shiftsst.com/blog/post/how-to-determine-the-rear-axle-ratio.html

2. Drive the car around, holding the speed constant. (use a GPS to get the speed car the Waze app has this information on the screen) collect GPS speed vs RPM for multiple gears

3. Get an tape and measure the wheel diameter in the rear

4. Come back and we can use some speed vs RPM calculators to figure out whats gear ratios the transmission has.

Doing this is will probably be the best in order to figure out what diff ratio you want.

I think 3.7 is a good option for a car that sees highway use. Once again its the LSD aspect that's the troublesome part.

[blodi]

7 hours ago, heyitsrama said:

@blodi pulling the rear cover off can be a pain in the arse because of the mustache bar. You could do this:

1. Calculate the diff ratio by spinning the wheels see https://shiftsst.com/blog/post/how-to-determine-the-rear-axle-ratio.html

2. Drive the car around, holding the speed constant. (use a GPS to get the speed car the Waze app has this information on the screen) collect GPS speed vs RPM for multiple gears

3. Get an tape and measure the wheel diameter in the rear

4. Come back and we can use some speed vs RPM calculators to figure out whats gear ratios the transmission has.

Doing this is will probably be the best in order to figure out what diff ratio you want.

I think 3.7 is a good option for a car that sees highway use. Once again its the LSD aspect that's the troublesome part.

1. I followed those instructions. With both wheels in the air and out of gear, the opposite wheel doesn't move. With the car in gear, the opposite wheel rotates the opposite way. 

I've tested the number of rotations a few times. With only one wheel off the ground, two rotations of the wheel= just over 3 1/2 rotations of the driveshaft. 

2. This will have to happen in the Spring when there isn't several inches of snow and salt all over the roads here. 

3. Tires are 205 55 15 Dunlop Direzza's, which should be 23.9"

 

 

[Zed Head]

14 hours ago, blodi said:

OK, I went back and found a post from 6 years ago when I had the trans rebuilt...here is what the trans guy told me:

1st- 33 Main 19 Counter=2.357

2nd- 28 Main 19 Counter=1.473

3rd- 26 Main 28 Counter=.928

4th- 22 Main 31 Counter=.710

5th- 19 Main 31 Counter=.613

 

His  math on 1st gear was wrong and should be 1.736 if those tooth counts are correct.  If you assume 4th is 1:1 and divide 1/.710 you get 1.408.  Take that times the numbers above and you get the wide ratio gears....other than first. So that one is a mystery still. Maybe I'm calculating this wrong? What if you assume 5th is 1:1? 

 

 

I fumbled around with some ratio calculations and your gear teeth numbers come up more like a very close ratio competition transmission.  Not a 3.321 first gear.  Fourth is always 1:1 on the Nissan transmissions I believe.

Tried to find a calculator to make it easy but had to go back to basic math.  One hard part of understanding the calculations is realizing that "4th gear" is not really a gear ratio.  It's direct drive through the shaft.  And, the gears that are called fourth gear are really just the gears that start the power flow through the gear set.  They're not really 4th, more like zero.  They are part of the ratio calculation for every "gear" that transmits power through the countershaft.

Found some illustrations.  https://www.artofmanliness.com/skills/manly-know-how/gearhead-101-understanding-manual-transmission/

 

 

[Zed Head]

Found another video that's pretty good.  Your first gear would be 2.45 by the tooth counts you showed.

I'm calling the gear set the zero gear set but I'm sure that there's another name for it.  Can't remember.  It's confusing because it is the "4th" in the transmission but has nothing to do with 4th at the shift lever.

"Zero gear" - 31 / 22 = 1.409
First gear set 33 / 19= 1.737
Result - 1.737*1.409 = 2.45
 

 

[blodi]

20 minutes ago, Zed Head said:

 

I fumbled around with some ratio calculations and your gear teeth numbers come up more like a very close ratio competition transmission.  Not a 3.321 first gear.  Fourth is always 1:1 on the Nissan transmissions I believe.

Tried to find a calculator to make it easy but had to go back to basic math.  One hard part of understanding the calculations is realizing that "4th gear" is not really a gear ratio.  It's direct drive through the shaft.  And, the gears that are called fourth gear are really just the gears that start the power flow through the gear set.  They're not really 4th, more like zero.  They are part of the ratio calculation for every "gear" that transmits power through the countershaft.

Found some illustrations.  https://www.artofmanliness.com/skills/manly-know-how/gearhead-101-understanding-manual-transmission/

 

 

You can see in my post above that 4 of the 6 comp transmissions actually have 5th as the 1:1.  The rebuilder told me 5th was an overdrive gear so I assumed it was one of the top two. However, if 5th was 1:1 and I do have a 3.54 rear end, that would add up to me seeing 4K at 80mph which is what I see currently.  I just couldn't get the other ratios to line up to any of those options. Maybe I need to put the back end up in the air, put in 5th and see if the driveshaft rotates exactly once with the engine being turned over once or if it goes a bit further which would indicate an overdrive. 

I played with this calculator a bit...

http://www.vmar.com/java/gear.html

 

Also, my 1st and 2nd gear are both really short and then 3rd seems tall by comparison...another reason the wide ratio seemed to make sense. The other one with a bit more of a gap from 2nd to 3rd is the last comp trans on the list. 

Edited January 28, 2022 by blodi

[Zed Head]

But wait (of course) you seem to be right in that there is a 5th gear direct drive.  Changes everything.

https://www.zcar.com/threads/nissan-competition-5-speed-direct-drive.304300/