What speedo gear do I need?

[AJV69 2]

Tried to do the formula that they have on CJ Pony but cannot get a result that makes any sense. I have a 69 Mach 1 with FMX automatic trans, 325 trac lock rear, 245/60R15 tires on rear and 225/60R15 on front. Anyone know which one I need. The speedo gear in there now is about 10 mph to fast at 50 - 60 mph.

[bigmal 225]

I didn't bother with the calculations. Each tooth on the gear makes about 5% difference to the reading. Look at what you currently have and get one with 4 more teeth. I would use a Speedo app to get an accurate reading as well. There are some very good ones out there.

[AJV69 2]

Hey Mate, I lived in Sydney (Wohlarra) in 1970 - 71, working for Philips, loved your beautiful country and did a 2 month safari trip before leaving. Thanks for your answer.

[bigmal 225]

45 minutes ago, AJV69 said:

Hey Mate, I lived in Sydney (Wohlarra) in 1970 - 71, working for Philips, loved your beautiful country and did a 2 month safari trip before leaving. Thanks for your answer.

Thanks mate, where are you in the US? I get there from time to time with work

[AJV69 2]

22 hours ago, bigmal said:

Thanks mate, where are you in the US? I get there from time to time with work

I live on the east coast in Jackson New Jersey...……….

[Brian Conway 264]

Ran your spec's thru the CJ Registry calculator and a 20 tooth gear should be about right.  I just finished some stuff with my trans/rear end and at 60 mph I was running right at 3300/3400 rpms.  The chart below verified the rpm and mph.  Brian 

[RPM 1,190]

On 7/24/2018 at 12:07 PM, AJV69 said:

Tried to do the formula that they have on CJ Pony but cannot get a result that makes any sense. 

This is the easiest way I know of to fix the speedo:

http://fyi.boardhost.com/viewtopic.php?id=7222