Gearbox Pinion Gear Question & Answer

[Paul_S]

I had the wrong pinion gear in my gearbox as it didn't match the rear diff ratio. The speedo was working but showing the incorrect speed.

So I thought I'd save a few quid and bought a new pinion gear (a blue one to replace a red one) and switches gears rather than the whole carrier. All went well (I thought) but now the speedo doesn't register anything. It just occurred to me that each gear is a different size and the carriers are probably subtly different to ensure the gears mesh properly. Does anyone know for sure?

I just dug up this photo from when I swapped gears and looking at this again I think I've answered my own question. I now notice '20' stamped in the carrier which would match the red (20-teeth) gear that used to be in it:

So now I'm on the hunt for an 18-teeth speedo drive...

 

[jonbills]

I don't think the carriers are different, but the pinions are offset in the carrier so you have to rotate it right to engage it in the drive in the speedo.

 

[Paul_S]

Ah, that could be encouraging. I did wonder about turning it but there is a flat and clip held in by a screw so I just lined that up dead straight.

 

[jonbills]

I think the trick is to slowly rotate the carrier while rotating the prop, at some point you should see the centre of the speedo drive rotating. You want just enough rotation to engage it.

 

[johnymd]

I did as Jon suggests and when I found a good position just recut the slot.

 

[Paul_S]

Great advice. I'll have the car on a ramp next weekend so I'll give it a go