I installed my 5 speed tranny last spring and put the correct pinion (black, if i remember correctly) BUT my speedo has not been working since. Worked fine before the swap. First i tought it was not deep enough in the tranny, so i shoved it in. Did'nt help. I swapped the pinion mounts (i had 2 of'em) and tried. No bueno.

Used a electric drill with speedo cable, and my oh my it moved. SO, what is the matter? Pinion is not ruined or anything, looks just fine to my eye just like the blue one i had in 4 speed. Why does it not work even i have pushed it way deep in the transmission?

When you installed the pinion gear did you use the complete aluminum assembly or did you remove the little pin and swap gears? The gear is actually offset to one side in the assembly and when Nissan changed the location of the hold-down screw they moved the hold-down slot to the other side. The two assemblies look the same but if you use a later assembly in an early transmission the gear will be too far away to be driven. People either cut a new slot or swap just the plastic gear.

Found a picture on the inter-web. Post #3.

Matching Speedo Gears after Rear End Swap - 620 - Ratsun Forums

I have 2 sets of aluminium assemblies. First i used the one that came with 5 speed, and then one from 4 speed. Neither of them worked. Both trannies have the hold down screw at the bottom of pinion...

Does the gear inside the transmission turn with the wheels? You could probably see in there with a mirror. I don't think much oil will drain out of the hole. Jack the back end of the car up to be sure it's higher than the fill hole.

That's all I got.

Correction, both trannies have hold down screw at the above, not bottom of aluminium mount. How deep must the pinion be in the hole? I wonder if i have overpushed it too deep

The gear assembly should be just deep enough that the metal lock-plate fits in to the slot. It's piece #63, in the upper right corner of this drawing. The slot should determine how deep the assembly sits.

Notice piece #65 also. It's the drive gear inside the transmission. I think that it might be plastic also and can get damaged.

Datsun 280Z Transmission Gears, Speedometer Pinion (5 Speed-FS5W71B) (From Aug.-'76)

I pushed mine to deep once, the sound wasn't nice and it didn't work.. then I saw the slot like zed head mentions.. it worked then.

Edited March 14, 201410 yr by bartsscooterservice

I had a similar issue when I put in a 5 spd. I rotated the speedo gear housing 180 degrees in the transmission, cut a new slot with a Dremel tool. Problem solved.

Cheers, Mike

I gotta try that, i can always experiment on the one i have loose before doing any "final" modificationos to the one installed.

I did the modifications to the pinion ring mount and installed it upside down. No effect

Seems your pinion is not hitting the driving gear in the gearbox. In other words it's not driven.

I took my Z to a shop and they confirmed that the fault is in transmission. Is that part somehow replaceable? Sucks not to see your current speed...