Tranny Speedo tooth gear housing swap - 280z 5 speed

[Rollins240z]

I searched and need some help changing my speedometer gear.

280z 5 speed tranny.  300zx  turbo clsd 3.7 diff

So I bought an 18 tooth “blue” speedo gear to match the ratio of my diff for an accurate speedometer reading.  I went to change it out and install new O rings and pulled out a purple 21 tooth gear.  The teeth part of the 21 teeth purple gear is larger in diameter than the blue 18 tooth gear I’m trying to swap out.  I did some research and my understanding is that the 20-23 teeth speedo gears use a different housing for the correct angle of the larger sized tooth gear offset.  Here is the link
http://www.classiczcars.com/applications/core/interface/file/attachment.php?id=1652

The 18 tooth gear shaft fits my housing perfectly, the only difference is the number of teeth and the diameter of the teeth.  Do I need a different housing for my 18 tooth gear or am I ok?  Z is not running so I can’t test it yet.  I also read somewhere that the housing can be turned slightly to accommodate the smaller gear teeth size.

[Zed Head]

For some reason clicking on your link only opens the same post again.  I managed to trick it though.  Looks like the 4.11 to 4.875 diff ratios use those cogs, probably why nobody sees the sleeves.  Weird that you would find one in your transmission.  You should have the correct sleeve in that transmission.

You could insert the sleeve and cog while turning the propeller shaft, in neutral.  It might be that somebody put the wrong cog in the right sleeve.  Odds are that the sleeve you have is correct for the 18T cog, since the other sleeves are like unicorns.

[Zed Head]

Shorter answer - somebody either swapped the high tooth number sleeve in to your 280Z transmission, or they swapped the high tooth cog in to your 280Z sleeve.  Either way, the 280Z sleeves are very common so you should be able to make the 18T cog work.  But your question can't be answered until you know which of the two possibilities you're dealing with.  A picture might help.

[siteunseen]

Seems like datsungarage/engine.com has some info on that?

[EuroDat]

I have never fitted a 4:11 or a 4:38 diff in a Zdd, but I think it's all in the way the adapter is fitted on the 20 and 21 teeth (red and purple) version. The adapters are offset and it could be just a simple case of spinning it 180 degrees. The adapter for the larger gears is the same as the smaller gears, but the locking tab slot is 180 degrees from the smaller gears version. That is when all other variables are the same.

I have read, on another website, that you can use a "wide ratio" 5 speed adapter in a "close ratio" 5 speed when using the red or purple gears. This would confirm the offset issue since those two adapter are 180 degrees apart.

You could try cutting the slot on the other side of the adapter, or pick up another one to suit the transmission. You are using a "wide ratio"? Any 280Z will do for a donor.

How to identify - F5W71B Wide and Close ratio transmission.pdf