speedo gear

Reply Subscribe

Thread Tools

Search this Thread

Oct 19, 2006 | 08:46 PM

'88_F-150

Thread Starter

Senior User

Joined: Feb 2005

Posts: 242

Likes: 1

From: Pittstown NJ

speedo gear

i have an 83 f150 with a np435 transmission and a np208 transfer case. It has 3.55 gears and 31" tires. i was wondering if anyone could tell me how many teeth the speedo gear needs to have.

thanks
rich

Oct 20, 2006 | 11:46 AM

jmteam6

Junior User

Joined: Oct 2004

Posts: 72

Likes: 0

If you know the number of teeth on the speedodometer drive gear the formula is easy take the speedo drive gear should be 6,7,8 teeth multiply by the rear axle ratio then multiply by the tire revoloutions per mile then divide by 1000.

6x3.55x686/1000=15
7x3.55x686/1000=17
8x3.55x686/1000=19

I am assuming you have 31x10.5x15 tires Inam not sure which drive gear your tranny came with all you have to do is take out the current speedo cable and you should be able to see the speedo drive gear to count the teeth if not try to get the color as they are color coded. Hope this helps you out.

Oct 21, 2006 | 12:33 AM

'88_F-150

Thread Starter

Senior User

Joined: Feb 2005

Posts: 242

Likes: 1

From: Pittstown NJ

the problem is i dont have the speedo gear so i need to know what gear to buy

Oct 31, 2006 | 09:55 PM

'88_F-150

Thread Starter

Senior User

Joined: Feb 2005

Posts: 242

Likes: 1

From: Pittstown NJ

anyone????

Nov 1, 2006 | 10:01 AM

jmteam6

Junior User

Joined: Oct 2004

Posts: 72

Likes: 0

The speedodometer drive gear is the gear inside the transmission This is the one that you need to count not the gear on the cable that mounts to the tranny. . If you need speedodometer gear that goes inside the transmission I would say that the setup you have get the 7 tooth gear.