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Differential swap in a 1978 280z

8K views 3 replies 3 participants last post by  Craig 
#1 ·
Ok,

I think I have the later 280b transmission in my 1978 280z but I'm not positive. This is the tranny that is found in the 81-83 280zx's.

I also think I have a stock differential which would be 3.54.

I want a lower gear ratio so I"m looking for a differential to install.

I have thought about the 4.11 differential from a 1985 200SX Turbo since I have heard that they drop in pretty easily. I know the half shafts from a R200 will bolt up but my 78 has a R180 right? Is this still an easy swap? What am I losing since I think this differential is not a LSD?

What if I wanted a 4.38 LSD differential? Where could I get one of those and what are the complications of installing one in my z?

I have also heard that the 3.90 from a 87-89 300zx turbo is a good swap but don't I need(want) a lower gear ratio to pair up with this tranny?

Anybody been here before that could share some info?

Thanks
Craig
 
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#2 ·
I also wanted a lower gearing in my 78Z. My rearend was good and I did not want to swap it out if I could help it. What I did was go to a 205 60 14 inch tire. That lowered the gearing enough that I could tell a seat of the paints difference! I changed the gearing in the transmission by two teeth to get my speedo to read the correct speed, so it must have lowered the gearing some, how much I'm not sure, maybe someone else could tell us both what my final drive is now. Hope this helps.



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#3 ·
Craig; Found your post overwhelming, but will help where I can.
The 78z 4 or 5 speed come with 280a trans or some call a ( wide ratio and a (R200) 3.54 diff.
The 4.11 or 4.38 are not direct bolt up, which will cost time to find plus $$$. You must be getting ready to do some serious racing. If all you want is bottom end then install a 4 or 5 speed from a 77-78-79z to the 4.11 or 4.38
The 81-82-83 non-turbo with manual trans come with a 280b trans or some call ( close ratio) and a (R200) 3.90 diff. This is a good pairing, and a direct bolt up to your z. This pairing gives you good bottom end plus mpg. This is the pair I have in my 78 bk pearl.
If I was after bottom end only, the 3.90 from the 81-82-83z N-Turbo, direct bolt up. 100 to 200 dollars, then a 4or 5speed from a 77-78-79z direct bolt up 50 dollars on the 4-speed 100 to 200 for the 5-speed. Then I would ask around what size tires are safe and help give me a little more bottom end speed. That would be my ticket.
I gave you these pairing as we stayed with the z, easy on the wallet, simple and oh so fast. Hope I was some help. Good luck to you. cec1936
 
#4 ·
Thanks for the reply.

I found the transmission calculator in some earlier posts and using it I figure that if I use 205/60/14 tires, I will get an effective differential ratio of about 3.90 (pretty close). That is assuming that the 195/75/14 tires that I have on there right now are the stock size.

I'm not doing any racing but I want more umph. I'm gonna stay away from differential swapping for now.

Craig
 
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