1933-34 Speedometer Gear Case

[Mike34]

I have a new set of 3.54 gears installed in my '34 axle. I need to swap out the drive gear (to 18 teeth.) I was looking at MACs which has the parts but I noticed that they offer the same gear case housing for both the Model A and 32-48 cars. I thought that there was a difference in the gear case housings for the Model A vs. Flathead years. Are they truly the same housing?

Thanks,
-Mike

[jetmek]

I think the differences are the case thickness is different depending on ratio to mesh properly with the drive gear on driveshaft

[Mike34]

Case thickness or gear diameter is what is different? I always thought that it was the gear diameter, which is based on the number of teeth (18, 19, 20) which would affect the diameter of the gear. Thus, you used thicker/thinner or multiple gaskets to ensure proper meshing of the gear.
I thought that I read a post (a while back) that said the diameter of the driveshaft tube was different, therefore the curvature (radius) cut of the gear case was different.

[DavidG]

The gear cases are the same 1930-34+.

[Andy]

I have an 18 tooth (3.54) case and a shaft. The gears and other parts available I think. $15?

[jetmek]

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On every 354 gear swap ive done it was necessary to sand the curved area to get the gears to mesh due to the smaller dia of the driven gear. Think about it. When you change to a smaller gear the center lines have to move closer for the teeth to mesh

[35fordtn]

We offer them for the square shaft (1930-48)

https://thirdgenauto.com/product/new...ly-3-54-ratio/

You can use a 18 gear in a 19 case but not a 21 case (without some modification)