Speedometer Gear Housing Differences

[A70Runner]

Are there different housings? 727 transmission. I have to put a 38 gear in. Know you have to clock the housing. Mine is only marked 21-25. Looked online to figure out how to clock it figuring I would see how. and don’t see any that are like this. All start 26-31

Thanks!

 

[Cranky]

Are there different housings? 727 transmission. I have to put a 38 gear in. Know you have to clock the housing. Mine is only marked 21-25. Looked online to figure out how to clock it figuring I would see how. and don’t see any that are like this. All start 26-31

Thanks!

View attachment 1945426

Don't recall having one that wasn't marked at each slot. What year transmission it that one out of?

 

[Cranky]

Posted by another member back many years ago....

The gear is installed into the housing off center. What I usually do is install the complete housing
into the tailshaft and rotate it until the gears are fully meshed. Then I just back off a little so there
is no pressure between the two gears, then clamp it down. Of course, it's nice to have the correct
housing, but everything's not perfect!

 

[A70Runner]

Don't recall having one that wasn't marked at each slot. What year transmission it that one out of?

74-75 400

 

[Cranky]

74-75 400

All I can say is try it like what's in post #3.....everything I had from the late 60's into the early 70's had numbers for each location....and the bigger the gear, the further away it needs to be from the output shaft gear. You can rotate it fairly easily if the O-ring is off of the adapter for a 'feel' of where the pinion needs to me then mark it.

 

[R413]

Yes that one is for less teeth. The other housing has 3 ways it can go into the trans. It starts at 26 and goes to low 40's I believe.

 

[Dipstick]

This one covers 26-45. The one in the OP is for later years when axle ratios were numerically lower.

 

[Vaanth]

Are there different housings? 727 transmission. I have to put a 38 gear in. Know you have to clock the housing. Mine is only marked 21-25. Looked online to figure out how to clock it figuring I would see how. and don’t see any that are like this. All start 26-31

Thanks!

View attachment 1945426

The pictured speedometer pinion gear adaptor, part number 2892994, used from 1969 - 1976, has only one setting for 21 - 25 teeth gears. This adaptor was used for the rear axle ratio of 2.45:1 in the 8-1/4" axle or potentially a tall tire with the 2.71:1 or 2.76:1 ratio. It can be used with the matching gear for other high ratios (low numerically) such as the 2.24:1, but by the time this ratio was released, the adaptor design changed to the plastic style.

The common multi point adapter, part number 2538608, used from 1966 - 1976 has three settings: 26-31, 32-38, 39-45, which covered higher ratios up to 4.56:1, or potentially 4.88:1 with a tall tire. Anything higher required the additional external ratio adapter.

The following image shows the part number 2538608 adaptor:

The following image shows the 1977 and later style plastic adaptor and differing pinion gear, FYI: