VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1912-1928 Speedo drive gears - which set for '28?

Hi all,

My parts book lists two possible speedometer drive gear combinations for my '28 AB Canopy Express:

1. Part number 432858 (4-10 teeth)

2. Part number 361964 (4-11 teeth)

Which one is correct? I notice that the driven gear in my tranny is 11 teeth. I'm replacing the torque tube and differential, so this area is open at the moment.

The speedo was indicating a speed of 15mph when I know I was going around 30 mph, so I took the speedo out and found it was missing a few parts and needed cleaning and lubing. This is fixed now. ;-)

Thanks, Dean

May be this can help you?
http://chevy.oldcarmanualproject.com/chevyresto/2841.htm

Thanks, Bluezone.

So, my truck has the correct speedo driving gears. I still need to figure out why it seems to be registering only half the correct speed.

I'll post more info as it surfaces.

Cheers, Dean

Sounds like you might have to get your speedometer calibrated on a speedometer machine.

Hi Dean,

If you check this posting on my blog about speedo restoration it covers calibration, which is realatively simple and can be done in your work shop. But if you have the cash to pay the shop to do the same thing, go for it.

http://my28chev.blogspot.com.au/2011/06/2009-speedo-restoration.html

Cheers

Ray

Hi Ray,

I read (and printed) your wonderful post. That article gave me the courage to open my speedo and play with its innards.

As I said earlier, some of the parts were missing, so I made it whole from parts from a couple of other speedos and made everything work smoothly.

Then, with a variable drill driving the cable (I set it up with a C clamp to adjust the speed and checked it with a digital tach), the speedo would not come up to speed, so to speak, even with the magnet slid up all the way. Any further and the magnet interferred with the housing.

I may end up at a speedo shop anyway. At least I know that all the parts are lubed and I'm not damaging anything by driving for now.

The investigation continues.

Thanks, Dean

To get your speedometer in calibration you will probably have to "zap" the speedometer magnet with an electronic magnet "zapper" like those used in conjunction with a speedometer calibrator machine.

Hey Dean it all depends on what the ratio is at the rear end ( crown wheel and pinion) that's why there is 2 different types. jim

Hi Dean I have a similar problem with my 28 , it reads slower than it is running and the culprit was the magnet in the speedo that engauges the dia,l, it was weak, don't know how you fix it, I imagine it is a critical measurement, but my speedo reads 30mph when I'm doing 60klm etc so I just double it and so I know I'm not speeding. RAY

Just an update:

I found a guy who has a speedo shop in Sacramento that still works on these older units. As you all predicted, the magnet was dead. He re-magnetized and re-calibrated. Cost = $65.00

Chuck at Commercial Speedometer in Sacramento, CA (1-916-371-5873) did the work.

;-) Dean