Speedo Cog Confusion

[Gary L]

This is on my 76 280Z 2+2 which has a 5 speed trany which a prior owner put in. The trany looks like it came out of an 81 - 83 zx (one tab on the tail and the speedo tab bolt is on the bottom @ 6:00). I notice my speedometer seems off (slow) so I pulled the speedo cog and it has 21 teeth. I checked the rear diff ratio and it is a 3.54 which means the speedo cog should be a 17 tooth. So I ordered a 17 tooth but when I got it I noticed it is smaller in diameter than the 21 tooth ( 13/16th vs 15/16th, resp). After swapping it in the pinion, which went OK, I put it back in the trany and sure enough it is too small in diameter to engage the trany sprocket to drive it. Anyone know whats not right here? For example, might this be some other type of 5 speed trany? Is the pinion wrong for the trany? I noticed it is offset, but it looks like it is offset for the early 5 speed trany (75-80; offset on the same side as the keeper slot) even though as mentioned above the tab and bolt make it look to be the late 5 speed. 

Thanks

Gary

 

[Zed Head]

Post some part numbers, or pictures, or something more descriptive.  Can't tell what you have, besides number of teeth and diameter.  Where'd you buy it, what are the part numbers, what was it spec'ed for, etc?  

I've had problems getting the speedometer cable to engage when reattaching it.  Get it all put together and it doesn't work.  There's enough room in the sheath to get it screwed on, but not engaged on both ends.   I've found that pulling the cable partially out and fitting the end in to the slot, then pushing both back in and screwing the clamp on works best.  The speedo end seems more forgiving.  

If you do it this way you can also twist the cable by hand to see if it the gears have meshed.

[Gary L]

In my above post, I meant to refer to the cog body, which holds the cog, as possibly being off set the wrong way for the later 5 speed. (not the pinion)

I ordered the 17 tooth (black) cog from The Z Store which list it as fitting zs through zxs. That's why I'm now  wonder if the trany has the wrong cog body (not offset to the correct side). It engaged the larger 21 tooth, but won't engage the smaller 17 tooth because the cog body is offset to the wrong side ?

I haven't hooked up my speedo cable yet, but when I put the new cog in the cog body and put it back, when I spin the drive shaft by hand the cog doesn't move so it must not be engaging.

Gary

 

[Zed Head]

33 minutes ago, Gary L said:

 After swapping it in the pinion, which went OK, I put it back in the trany

In my above post, I meant to refer to the cog body, which holds the cog, as possibly being off set the wrong way for the later 5 speed. (not the pinion)

How about a link to the part you bought?  Something.  Can't tell what you've got, plus I wrote a whole thing only to find out you haven't even hooked up the cable.  I'd search the web for it, but there's a football game on.

Remove the cog housing clamp and spin the housing to see if it grabs.

[Gary L]

It looks like I have the later 5 speed as shown in the below link but if so the cog body is offset the wrong way.

http://www.oocities.org/inlinestroker/ratio.html

Of the different cogs available, it had a purple 21 tooth it it and I bought the black 17 tooth the z store. part number 21-7181

 

As I noted, I know its not engaging because when I spin the drive shaft by hand the tail end of the cog where the speedo cable hooks to doesn't move.

Does anyone know where I could check on buying a cog body for the 81-83 zx?

Thanks

Gary

[Zed Head]

You can spin the cog body/housing 180 degrees and grind a new slot to clamp it.  It's common.  If you don't have the housing pressed all the way in and clamped the teeth won't mesh.  You might also eyeball the gear inside the trnsmission, they get damaged easily.  Plastic also.  That would be a bummer.

Nissan and MSA call it the "sleeve".

Weird that you have a bigger gear, the 21 tooth. that worked.  Maybe there's a whole other option out there for using the Z sleeve in the ZX transmission, bigger gears.  Is your sleeve steel or aluminum?  I have 280Z sleeves that are steel, and ZX that are aluminum.  Might be a clue.

Have fun.

[Zed Head]

http://www.nissanpartsdeal.com/parts-list/1982-nissan-280zx/manual-transmission-transaxle-fitting.html

http://www.ebay.com/itm/Datsun-240Z-260Z-280Z-280ZX-Speedometer-Pinion-Gear-Assembly-17-Teeth-NOS-RARE/281911519035?_trksid=p2047675.c100011.m1850&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D35220%26meid%3D73b6c4a5b3be48ba88030b8c78c06b1a%26pid%3D100011%26rk%3D3%26rkt%3D6%26sd%3D272044749214 (iffy, the guy doesn't know about the different slots)

http://www.partsbase.org/parts/nissan-3270778000/ (click the + sign and it will show other cars that use it)

[Gary L]

I didn't think about spinning it 180 degrees and grinding a new slot. When I get a chance I'll have to slide it back in turned 180 degrees and see if then it spins. The gears in the trany look fine ( I can see them pretty well). The cog body is aluminum, not steel, so it must be from a zx. I think I saw somewhere that the 21 tooth was for a 4.375 rear diff.

As for the football game, I guess I'll have to go with the Patriots again since I'm a Michigan Alumni like Brady.

Thanks

Gary

 

[Gary L]

OK, so I just ran back out to the garage and put the speedo cog back in the trany with the keyed slot turned 180 degrees and it works --- when I spin the drive shaft the cog shaft spins so I know it is engaged

Since it is aluminum. it should be easy to grind a new keeper slot. If I mess it up then I'll have to look into a replacement, as long as I don't mess up the gear in the trany it engages.

Thanks again Zed Head

Gary

Edited January 24, 2016 by Gary L

[Zed Head]

I think that I actually have a 76 that is steel, and a 78 that's aluminum.  Either way, good luck with it.  I'd use a file rather than a grinder, just for the precision.

Manning's last chance.  Got to root for the old man.