Ok I have a 65 impala completely stock set up including tires with 14 inch wheels and a 12 bolt rear with 307 gears what plastic gear do I need in my Muncie m20 trans?
Correct plastic speedo gear
- Thread starter 63impalass409
- Start date
It depends on the tire diameter. My GM catalog states that there are two options for the driven gear with a 3.08 axle. Original tire size of 7.00 or 7.50 x 14 uses a 18 tooth gear, # 3987918 (brown colored gear). For tire size 8.00, 8.25 or 8.55 x 14, a 19 tooth gear is used, # 3987919 (natural color gear). Convert your current tire size to the examples listed above and you should get your correct gear.
Carl 1962
Well Known Member
When I fitted a TH350 to my 62, in place of a PG, I used this calculator where you input all the info (including gearbox type) and it tells you what color and teeth gear you need. It's an Aussie site, but it told me which speedo gear I needed and it was spot on. My speedo reads perfect. http://codes.oldholden.com/Speedo/
Thanks guys Very helpful
If search this site, you will find some great documents posted by Cecil that lists all of the gear and tire combinations. I'm on my phone right now so I too hard to search.
Here is a link to another post by Cecil. It has some TSB with great information http://www.348-409.com/forum/threads/many-new-charts-added-to-the-library.25604/#post-220601