Clocking the Speedometer Gear Drive

[magik235]

I searched the site but could not find the answer.
I have a 1987 Jimmy with a NP208 transfer case. I have 35" tires with 4.56 gearing. I bought a 39 tooth speedometer gear to replace the 35 tooth. I can't find a reference mark on the transfer case to align with the 39 on my speedometer drive. How to you clock the speedometer gear drive unit?

 

[magik235]

I installed a 39 tooth speedometer gear replacing the original 35 tooth gear. There isn't any reference mark on the transfer case. There is a dot on the hold down fork. When I aligned this dot with the 39 on the speedometer drive the speedometer did not work. I had to clock the speedometer drive by feel to get the speedometer working. The picture below shows my final clocking.

 

[DeviousK5]

It looks like you need to clock it 90degrees counter clockwise. I havent swapped many speedo gears personally but the info should be helpful. If the gears are the same diameter clock it 90 . the hold down on the speedo housing "locks "into the recesses normally

EDIT: if your orig gear ratio was 3.73:1 the old speedo gear should be damn close

 

[4X4HIGH]

There is no clocking that needs to be done. Remove the driven gear housing, swap the 35 tooth gear for the 39 tooth gear then re-install the driven gear housing. Keep in mind that there are 2 different driven gear housings and each one will accept a range of driven gears so you might need to replace the driven gear housing as well. The range of gears that they will fit are cast into the housing usually around the outer edge.

 

[DeviousK5]

Yeah but from the PIC the hold down isnt sitting on the housing correctly and thus would ultimately need to be turned 90degrees counterclockwise after the new gear has been installed

 

[magik235]

Thank you for the information. I moved the speedometer drive back to the original position and everything works.