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Time for diff and transmission swap, what more to change?


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I have got myself an 3.9 r200 and an zx transmission ( have been sitting in an barn for 14 years )that will go into my 240z -73. I have the m-bar, axels, new diffmount for the diff. I need to get some gaskets, which should i get? Do i have to change every gasket/seal in the diff and trans?(trans only has 48000 original km on it). And i want your opinion what more to change when iam taking it apart./Andreas



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Hi Andreas,

I rebuilt mine transmission last year in the 280Z. It has the ZX tranny and the R200 3.9 ratio. The 71B tranny came in the 280Z and the ZX, but the ZX has a cross ratio version.

IMO If your going to dismantle the tranny:

- I would at least replace the bearings, O-rings, Lip seals and front yoke gasket. Nissan sells all the parts separatly. You can order a aftermarket bearing kit from the US which is not complete by all means, but its easy to order them at your local bearing supplier. There are some bearings that need to be sourced from Nissan.

- The 3 nylon bushes in the selector are a must and make it feel like new. Gets rid of that "stick in the mud" feeling when changing gears.

- Replace the shaft nuts (main output shaft is left hand thread).

- While its out, good time to check the clutch and replace the release bearing.

Your speedo gear should be the right one for that diff, if the diff came out of the same ZX. Depends on your tyre size for true speed readings though.


- Rear cover gasket and breather.

- Pop the side shafts and replace the seals.

- if the pinion seal is not leaking, I would leave it in. You can replace it, but sometimes it will whine after because the pre-load and alignment gets mucked up a little bit. It doesnt take much to start whining and its hard to correct.

If you need part numbers, Ive still got my shopping list somewhere and can scan it in if you want it.

You will also have to do something about your driveshaft. It will be too long for the five speed. You will need to get it shortened or a series I driveshaft.



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On the driveshaft, Chas - You might be thinking of the 71C transmission with the 71B bellhousing swap.

1973 will have the 71B four speed, so the 71B five speed should drop right in with no driveshaft change.

Your right Zed thanks for the correction, I was thinking of the 71C swap I am planning this coming winter:stupid: I realised it too late and Mike had the website down for maintenance.


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Chas: Thank you. I have sent an order to Msa for the seals and gaskets you recomended. I also bought a new speedogear, the white one. In the trans there was a blue one.

Chas, do you feel big diffrence in your car with the 3.9 diff and zx trans. I hope it makes it notable quicker.

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Hi Andreas,

It wont be quicker of the mark. The close ratio box with its "taller" first gear defeats the advantage the 3.90 diff will give you. Once your moving its a lot different. The close ratio transmission and the 5th gear with work a lot better. The spred across the ratios is a lot smoother than the overs transmissions.

I made a table for my 280Z when I was buzy planning my swap. I added your 4 speed to it to give you an idea what you will end up with.

Hope that helps.



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