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R180 differential button swap to 4.38 diff


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So the story is I have a 71 zed. I swapped an 83zx 5 speed and now I want to take advantage and put a 4.38 diff in.

 

4.38 diff out of a 83 nissan 720

 

I did the "button" swap from my old diff into the new 4.38 diff.

 

A couple problems. The side gears or "buttons" from my old diff looked noticable smaller than the ones coming out of the 4.38 diff. Teeth count were the same though.

 

Once I reassembled everything and Torqued things to spec I noticed the sides gears has a little bit of gap. I can bolt in the axle stubs and move the stub in and out 1/8th of an inch or so. I did use all the same spacers and kept them in correct order for the 4.38 diff. There is a formula to calculate side gear gap but it requires me to disassemble the diff and measure the spacer and other things.

 

There is also some noise when I spin one of the stub axles which I have posted here: https://youtu.be/TKesvom5MZo

Any help???

Edited by abdi
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Hmm the 4.11 I have felt super short, I can't imagine how that would feel with a 4.38. 

 

You can see the side gears moving in and out so you definitely have some slack somewhere.

 

http://forums.hybridz.org/topic/49194-differential-cv-lsd-hp-torque-r160-r180-r200-r230-diff-mount/

 

Has a post about early R180 being 110mm vs 115mm, might account for the gear gap.

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4.38 is gonna be wicked. But by the time you factor in my 17 inch wheels it's probably a 4.11.

 

So I found the problem. I swapped the old side gears into the 4.38 diff. When all you have to do is push the buttons out of the old side gears and press them into the 4.38 side gears. And of course remove the c clips from the 4.38 side gears. Now it's tight as a drum. So excited!!!

Edited by abdi
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Well glad you figured that out.

 

I will say it was fun going almost to redline in two gears on freeway on ramps and still being below the speed limit, but the drone at 3k rpm going about 65 was pretty terrible. I just ran the math and it says you will be at 3300 rpm if not higher depending on your tire size.

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