4 speed vs 5 speed info?

[72240Z]

I'm debating swapping out my 4 speed in my 72 for a 5 speed. I've read through about 30 posts and still have questions.

As I understand it, I have a type B transmission with a built in bellhousing, and an R180 rear diff with 3.36 gears.

I've seen references to 2 different 5 speeds, the late Z, not sure on years, 77-78 only? and the ZX 5 speed, which was 79-8?

I've not been able to find gear ratios for any of these transmissions. I understand that the overdrive is taller in the ZX trans. Can anybody provide specs or point me to an existing chart?

What about physical fitment? do they bolt in with the same crossmember, fit through the hole in the floor properly, and length? Does the driveshaft need to be shortened?

Thanks,

Devin

[IdahoKidd]

Start here

http://www.classiczcars.com/forums/showthread.php?s=&threadid=1957

and look here

http://www.zhome.com/ZCMnL/tech/GearRatios.html

Edited January 22, 2011 by IdahoKidd

[sblake01]

Also look here:

http://webspace.webring.com/people/cz/z_design_studio/

Edited January 22, 2011 by sblake01

[tlorber]

I believe the ZX came out in '81. You should pull the cross member off your 4 speed and put it on your 5 speed. Keep the drive shaft from your 4 speed since the 5 speed has the same dimensions. I used the shifter from my 4 speed as well (my tranny is an '82) You will need the bend in it or it (a newer, non bent one) will hit the front of the tunnel hole.

Make sure the throwout bearing collar, fork and pressure plate all come from the same car-doesn't matter which one, but they all need to go together. As stated in one of those posts, the 3.36 will be a bit tall for a 5 speed. As stated, if you swap the diff, change out the speedo pinion gear to preserve accuracy.

[Nissanman]

...and also here.

[sblake01]

i believe the zx came out in '81.

1979.

[72240Z]

Great! That's just what I was looking for. My only other question is how do I physically identify one versus a 4 speed or one from a 510 or something else? are there numbers on the case or ??

Devin

[tlorber]

1979.

I sit corrected.

[sblake01]

Great! That's just what I was looking for. My only other question is how do I physically identify one versus a 4 speed or one from a 510 or something else? are there numbers on the case or ??

Devin

Transmissions for a 510 are shorter that the S30/S130 transmissions.

[Jetaway]

Great! That's just what I was looking for. My only other question is how do I physically identify one versus a 4 speed or one from a 510 or something else? are there numbers on the case or ??

Devin

I think all manual 280ZXs were five speeds.

My '72 came with a 280ZX tranny installed but with, I presume, the original (manual transmission equipped) differential and the speedo indicates aprox. 15% too low with P215/60-14s. (For example: An indicated 52 mph is an actual 60 mph.) After playing with the numbers I concluded that when the 5-spd was installed they used the speedo pinion gear from the 5-spd.

I bring this up because another post in this thread says that you only need to change the pinion gear if you change the differential. I think that was based on a rather oddly worded statement in the first post of the thread you were directed to begin (thread id# 1957). It said, basically, that to be accurate the pinion gear has to match the differential ratio. Which is absolutely true, but the pinion gear isn't driven off the differential output but the output shaft of the transmission. At the factory the pinion gear in the transmission is chosen to match the installed differential. While I was playing with the numbers to track down my speedo error it became pretty clear that Datsun aimed to have the same number of engine revolutions per mile in top gear regardless of whether the 4 or 5 spd. was installed which meant a higher (numerical) differential ratio with the 5 spd than the 4 spd. Which also meant a different pinion gear was installed with the 5 spd. than the 4 spd to keep the speedo accurate.

So, if you want to avoid doing some experiments and then math in your head to convert your indicated to true speeds, you'll need to match the pinion gear to the differential installed in your car. And that pinion gear, my friend, you will find in the 4 spd that you are pulling, not in the 5 spd you are installing. Assuming, of course, the speedo is currently accurate. I've not done the work myself, but based on repair manuals, the pinion gear swap seems to be a pretty simple and straight forward procedure.

Chris

[IdahoKidd]

There is beginning to be some misinformation. Go to

http://datsunzgarage.com/engine/

I cut and pasted this section from there but it left the pictures out. Read all about the transmissions and the speedo gear section.

Chris is using the wrong word for the speedo drive gear. The pinion gear is in the rear diff and is a major event and you do not want to fool with it at all at this time.

__________________________________________________________________________

Nissan called the '77-80 trans a "wide ratio" while the '81-83 was called a "close ratio" 5-speed. The early one has the lowest 1st/2nd gears for acceleration, but a wide spread between 2nd and 3rd. The later one has a taller 1st/2nd but a tighter spread between 2nd and 3rd. It also has a much taller 5th for cruising. Your choice.

According to a Z Doc friend who rebuilds transmissions the early 5-speed is a 4-speed with 5th and reverse sharing the same fork. He said it's common for people to "blow" 5th gear as the fork is weaker. He stated the later 5-speed is a genuine 5-speed which is stouter. I call the early one a 280a and the later a 280b to keep them straight.

Keeping the speedometer correct

Everyone gets confused about how to calibrate the speedometer after swapping differentials, it's actually very easy. The speedometer is metered by a plastic, toothed cog on the end of the speedometer cable that screws into the transmission. This cog is paired with the differential, not the trans. So it doesn't matter which trans you have, all you do is select the proper cog for the rear-end ratio you have in the car. While they are colored for easy identification, the Nissan dealer only has them in their parts list as "17, 18, 19, 20, or 21" tooth cogs.

YELLOW is the 16 tooth for the 3.36

BLACK is the 17 tooth for the 3.54

BLUE is the 18 tooth for the 3.70

WHITE is the 19 tooth for the 3.90

RED is the 20 tooth for the 4.11

PURPLE is the 21 tooth for the 4.38

Don't rely on a junkyard Zcar to have the right colored cog

~When in doubt, count the number of teeth~

NOTE: There are 2 different aluminum cog "sleeves", a '75-80, and '81-83 with different cog "offsets". If you look closely in the picture above notice how the red cog is offset slightly to the right, and the blue to the left. This means you must keep the sleeve with the transmission it came in, and only swap the cog. Otherwise the cog may not mesh the proper way inside the trans.

On 240's, you will have to cut about 2 inches of metal from the front/right edge where the shifter goes through the trans tunnel when using a 5-speed. Otherwise the throw into 5th gear will hit. This cutting is the price of a 5-speed trans and is not a big deal at all, the console covers it.

[tlorber]

One way to think of it is that, in 4th gear, both 4 and 5 speeds are running straight through = 1:1 ratio, (the overdrive on the 5 speed then lowers this ratio depending on the specific tranny). At this point the only thing affecting speed (other than rpm's) is the differential. The speedo gears are all color coded to match the diff. I believe I got my 3.70 from Z Specialties ($22.00 IIRC). Pretty easy to swap-take the speed assembly out of the tranny, drive out the roll pin which is in there pretty tight, insert new gear, reinsert roll pin, put back into tranny and obey the speed limit now that you have no excuse.