[stancil]

I'm looking for an educated guess on what size speedo trans gear I should start with....Being the trans didn't have one to start with to know if I had a correct speedometer reading. I have a Munci 4 speed and not knowing the gear ratio. The side of the trans has the numbers 8925660. Under those numbers US Pat No 3088338. Under that reads General Motors Corp. I also found P0K 5B stamped vertically. The rear of the trans has 3857 584GM. The rear end is a 10 bolt and I'm unsure of the gear ratio. I have the bullet, bolt and tab to install the speedo trans gear. Also if I could get any insight of how to install the gear and anything to be careful of installing it would also be appreciated. Any part numbers for the gear I would need? Thanks!

[KevinW]

Chris, take a flashlight and look into the gear hole. You will see the drive gear. Mark one tooth with a sharpie marker. Then spin the trans and count the teeth. Then measure the diameter of your tire. The jack up your rear and spin a tire while watching the driveshaft (count the revs of the driveshaft). Armed with those 3 numbers (drive teeth, tire dia amd rear gear), you can choose which driven gear you need from this site:

http://www.novaresource.org/speedo.htm

good luck!

[stancil]

Thanks for the reply Kevin. Maybe I'm overthinking this...If the gear inside the trans has X number teeth and is a fixed diameter. Then how is it that different sized speedo gears can be used and still mesh with the plastic gear inside the trans?

[KevinW]

If you notice from the website, certain gears only work with certain drive gears.

[stancil]

OKay Kevin...I hope your still with me. Or anyone else for that matter.LOL. I got my speedo gear and I was wondering what prevents the speedo gear from falling back out of the bullet and into the trans once everthing is installed? Thanks in advance.

[KevinW]

I'm pretty sure there is a stop on the inside plus the rotation probably is pushing it outward.

[stancil]

Thanks again Kevin!