Indexing the speedo pinion, one for BLUE?

[5thhorsemann]

So I've been having speedo problems of late and decided to check out the speedo drive pinion. Upon removal I noticed the housing is not keyed and it has an eccentric or offset pinion shaft boar. As I rotate it 360 degrees (the housing), I can feel the pinion gear engage and disengage at certain locations as I turn it. Now at this point my pinion gear is trash, so no matter where I index it, it will not drive the speedo for long (this being the problem I am experiencing). I will get a new pinion this week, but my real question here is, where is the gear that drives the pinion in relation to the center of the hole? (12 o’clock’, 3 o’clock, etc.) I realize the eccentric housing is such to accommodate the larger and smaller gears, but none of my manuals contain information on how to index the housing thereby timing the pinion to the drive gear.

That said, I need a new pinion, my tire size is P235/60-14, they are 24 inches tall. What would be the most accurate size pinion 16 tooth, 17 tooth, etc. It had a 16 tooth which I think is the original, but the PO was running P225/60 -14’s and may have changed it. I’m thinking a 17 tooth may be more accurate with the taller tire, what do ya’ll think?

[5thhorsemann]

I just was doing a thread search and I realized that the above assumptions may or rather are flawed. I made these assumptions based on how the pinion housing was installed by the PO. Is the slot that is cut in the housing designed to accept the keep bracket? I just moved the housing to that position, and the fitment looked perfect, but with the torn up pinion the speedo doesn't work at all. This is driving me crazy, and without a good part to install I can't get this out of my head.

[5thhorsemann]

Bump the thread, can't find any info in my manuals or thread searches. HELP!

[Zed Head]

The slot in the assembly is designed for the "plate-lock" (Nissan term, #63 here - http://www.carpartsmanual.com/datsunS30/DatsunZIndex/PowerTrain/TransmissionGears/5Speed/tabid/1708/Default.aspx.) It determines the orientation and the depth of the assembly. The later 5 speeds have a different assembly than the early 4 and 5 speeds.

I have the 17 tooth gear in my transmission,with 3.54 rear gears and 205-70/14 tires (25.3" dia. by internet calculator), and my speedometer works perfectly. The same calculator shows your tire as 25.1", so the 17 tooth is probably as close as you'll get, IF you have 3.54 gears. http://www.1010tires.com/TireSizeCalculator.asp?action=submit

Swapping gears looks pretty easy, a small roll pin just needs removing and replacing. Any stock 280Z with an R200 should have a 17 tooth gear, I think that they all came with 3.54 gears.

I have 76 4 speed, 78 5 speed and 83 5 speed in the garage. I might be able to get a picture if you know what you're looking for.

Here's a couple of links, that you may or may not have seen that might give you some ideas -

http://www.geocities.com/inlinestroker/ratio.html Look down at the bottom of this page.

http://home.comcast.net/~zheimsothtn/transmission3.htm Note - the picture in this link doesn't tell the whole story since there is actually an upper and lower lock plate orientation for early and late B type 5 speeds. It has good pictures though.

Edited November 29, 2011 by Zed Head

[olzed]

After I changed diff ratios, I found it was a case of trial and error finding the correct speedo pinion. Luckily I have a friend who had an assortment.

[5thhorsemann]

Thanks for the info Zed Head, helpfull stuff