Speedo gear housing markings

[Dodgeboy]

I am replacing my speedo gear (tranny is a 1976 B727), going from 25 teeth to 37 teeth. My housing however only has the markings for the 21-25 tooth and nothing else. The new housings don't have a alignment mark for 21-25T but do have a blank spot on it. Can I assume this spot would be for the 21-25T gear? I'm just trying to figure out how to align my housing

 

[413]

You have both in Your hand, spend some time looking at them and you tell us what the difference is.

they did not forget to mark them.

 

[Chryco Psycho]

there are 3 different gear diameters , you can put it in with the gear center furthest from the trans main shaft & then see if you can rotate it so it is closer ,if it will rotate it needs to be closer if not it is in the correct position .

 

[Dodgeboy]

there are 3 different gear diameters , you can put it in with the gear center furthest from the trans main shaft & then see if you can rotate it so it is closer ,if it will rotate it needs to be closer if not it is in the correct position .

I will try that and I hope it works.
I did some more googling and it seems there are 2 different housings. One only has the index for the 21-25T (the one i have), and the other housing has the indexing for the 3 groups (26-31, 32-38, 39-45).

 

[Chryco Psycho]

ok but the offset for the pinion gear shaft remains the same

 

[Dodgeboy]

It works, thanks guys for your input. Now I just gotta get the correct speedo gear. Looks like i was off by 3 teeth, need a 40T not a 37T. Speedo is off by 8 mph but 100x better/more accurate then the 25T gear that was in there, shoulda done this 20 years ago....lol

 

[Chryco Psycho]

Coool , what gears are yo running , 3.91?

 

[Dodgeboy]

Orginally 2.76, then tried 3.23 (both gears with factory tires) and now 4.30 with 29.9" tall tires.