speedo drive gear

M

mike37cdn

Senior Member
I got pulled over for going a little to fast in my 1928 two door said i was 10 over speedo must be out i looked at the numbers on the housing it had 10-37 is this the right one for my car i think i have a 3.78 :1 in it i guess i need to speed up the drive witch gear do i need thanks mike
 
if speedo is reading slow you need a smaller drive gear at the trans, if its reading fast you need a bigger gear at the trans, usually one tooth up or down will change speedo reading 3 to 5 mph
 
mike37cdn said:
I got pulled over for going a little to fast in my 1928 two door said i was 10 over speedo must be out i looked at the numbers on the housing it had 10-37 is this the right one for my car i think i have a 3.78 :1 in it i guess i need to speed up the drive witch gear do i need thanks mike
Click to expand...

If you have 3.78 gears you need a housing with 19 on it (you might want to double check since when rebuilding the rear end restamping the housing is not a high priority). In California the AAA will test your speedometer in the car. They do this in each office at different times of the year. You might try your local auto club and see if they provide this service. If you have the right gear and your speedo is off have it rebuilt (in my opinion). If you just change the gear to compensate for a worn speedometer your odometer will be off. You might want to try checking your odometer on a measured mile and see if it is accurate. If your odometer is accurate, I would definitely consider having the speedo rebuilt.

Charlie Stephens

Followup: Reading Aerocrafts post and thinking back I realize you probably meant that the 10-37 was stamped on the speedometer gear housing and I assumed you were reading the number stamped into the banjo housing (I think this was a practice on the Model A but I am more familiar with the later cars). I recommend you roll the car forward in high gear and see if you get 3.78 revolutions of the wheel to one revolution of the engine. You probably don't want to trade an inaccurate speedo for an inaccurate odometer. Of course the low cost solution is to just remember the speedo is off and compensate in your mind.

Charlie Stephens
 
Last edited:
The 10-37, a 3.70:1, was common in 1928. I suggest that you probably have an 19 tooth drive gear at the drive shaft end of the cable where an 18 tooth would be more appropriate. That will speed up the cable and more than likely bring the speedometer reading into line with reality.

I suggest that you remove the housing that is marked 10-37 and look at the drive gear. The suppliers have a selection of gears available. It is very easy to change the gear. Gar Williams
 
Last edited:
Hi Mike,
You may want to verify your current MPH reading againt a GPS, I am sure you or someone you know has a hand-held. I have used this and my Tudor is only about 2 mph slow at 45 MPH according to this device, I assume it to be correct.
Just a thought..Scott
 
Last edited:
Mike,

I see you live in Canada. If your speedometer reads in mph and the speed is posted in kph. I think I see the problem :>)

If you are running an overdrive, of course, the speedometer will read way too low and the speedometer gear won't correct for that.

I think anyone who gets a speeding ticket in a Model A should be proud and display it on the windshield where ever you stop.

Richard
Anaheim CA
 
Yes a ticket would be cool but he liked model a,s i checked it with my gps at 45 i was doing 58 on the gps mph i do not have over drive the car is all stock i wiil take the housing of and count the teeth so i will need less teth to speed up the cable the speedo head was rebuilt thanks mike
 
Could also be the speedo itself. A speedo works by having a magnet spun inside a cup and the cup is turned against a spring so it doesn't continue to spin, but stops when the forces are equal. If I recall corectly, an input of 1000rpm is 40mph. The rpm is not engine/driveshaft rpm but the rpm of the speedo cable. If I've got the wrong rpm, someone here will correct me. You could take the speedo out and get it tested.
 
You must log in or register to reply here.
Back
Top