zl71b #2 in a 73' 240z?

[edl0c]

hello my name is Edward. I have a 1973 240z with a 4 spd and wanting to put in a 5 spd. I got a 5spd out of a 1985 nissan 720. The numbers say ZL71B #2 and the whole trans is 26in which I found out is a short trans and a 240z has a 31.5in long trans. Few questions are would i have to get a longer driveshaft and what other mods are needed to swap the 5spd? I can get my hand on a L- series bolt pattern front case. My Z for now is just going to be a cruiser. Also I found what i believe are the gear ratios for this 5spd on http://zhome.com/ZCMnL/tech/GearRatios.html 1st. 3.321, 2nd. 2.077, 3rd. 1.308, 4th. 1.000, 5th. 0.833. My car has a 3.364 in it now. Since my car will see highway travel @80 most likely and will not be racing will my highway rpm be lower or higher and will gas mileage be better or worse?

[datsunaholic]

Well, you won't be able to use your center console if you have one, as the shifter will be where the radio goes.

[datzenmike]

Edward to make things a lot easier get a long 31.5" 5 speed from the later 280z or first year ('79) 280zx or any year 810/Maxima. These will have the 3.321 first gear and you will not have to swap the front cast or shorten the driveshaft. The '80-'83 280zx will also work but has a 3.062 first gear and 1-4 gears that are 'closer ratio' and favors highway driving over city stop and go. It also has the highest overdrive ratio.

 

Converting the 720 5 speed you will need to lengthen the driveshaft as mentioned and the shifter will move forward about 5.5". Your transmission mount might work with the shorter tranny. You can use your 4 speed front case and swap it onto the '85 transmission BUT (there's always a but) you will have to remove the larger 62mm counter bearing and press the 56mm one from your 4 speed onto it. Also the 1st/2nd shift rod hole in the 4 speed case will need to be drilled out from 14mm to 16mm for the larger diameter 85 shift rod.

 

Keeping your speedometer accurate when swapping transmissions.

 

First of all the speedometer drive gear in the transmission is intimately mated to the differential ratio. They work together and should not be separated.

 

If you are swapping in a new transmission the old speedo pinion should go into the new one to keep it with the old differential.

 

But not so fast, there is a small problem with this. Changes were made to the 71B transmission and pre '80 speedo pinions will not fit '80 and newer FS5W71B transmissions... BUT they can be easily modified and made to fit.

 

All pinions have a small key way slot in their sides that a locking tab fits into, and this tab is held in place with a small 10 mm bolt. Pre '80s pinions have the slot exactly 180 degrees around on the other side compared to the '80 and up pinions. So, all you have to do is cut a new slot for the tab. I used a small angle grinder and a $4 metal cutting disc. All I did was cut a slot that the lock tab will fit but on the opposite side.

 

This isn't the one I made because it worked the first try and I wasn't about to drain the tranny and take it out for a picture. This shows the key way.

 

 

This one has a second key way cut in it and allows an older pinion to work in the newer transmission.

 

 

 

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