Speedometer gear

Postby **mrpham** » Fri May 24, 2013 9:33 am

Hey all!

Just trying to do some research on what speedo gear I need after I install my 4.778 rear diff ratio.

I gather that the 4.3 ratio diff uses a 20 tooth gear, the 4.1 uses 23 tooth.

Since the 4.778 ratio is roughly 11% shorter, does this mean I need a 18 tooth speedo gear?

http://www.solomiata.com/Drivetrain.html

John.

Postby **mrpham** » Fri May 24, 2013 9:43 am

Info out there seems to contradict each other.

Another source says that the 4.3 uses 23T and the 4.1 uses 22T.
If that's the case than I would need a 25-26T gear?

lizard · Postby **lizard** » Fri May 24, 2013 10:02 am

Just fit one of these and calibrate with your GPS

http://www.yellr.com/yb_home.htm

Postby **mrpham** » Fri May 24, 2013 10:19 am

I've got an NA so it's a cable dríven speedometer not digital like the NBs.

geofiz · Postby **geofiz** » Fri May 24, 2013 11:16 am

Swap the cluster for an NB one and go digital.

Tony · Postby **Tony** » Fri May 24, 2013 12:26 pm

4.3:1 speedo gear to suit NB8A box is green with 23 teeth.

Presumably this gear will also fit the NA cable drive set up, but it may be difficult to find an OEM speedo gear to suit 4.77:1 ratio.

Others with more knowledge than I can advise.

Steampunk · Postby **Steampunk** » Fri May 24, 2013 1:22 pm

Is the actual plastic gear on the sender removable? If so, then perhaps bring to a wrecker and undo front-wheel-drive speedo senders (accessible from engine bay) from Mazda & Ford (and some Kia) and compare?

Postby **mrpham** » Fri May 24, 2013 6:21 pm

Steampunk wrote:Is the actual plastic gear on the sender removable? If so, then perhaps bring to a wrecker and undo front-wheel-drive speedo senders (accessible from engine bay) from Mazda & Ford (and some Kia) and compare?

Looks like Maruha sell a gear drive for diff ratio of 4.6, probably the closest solution.

http://www.maruhamotors.co.jp/parts/grivengear.htm

sailaholic · Postby **sailaholic** » Fri May 24, 2013 7:54 pm

Your car is an import yah? If so was the speedo way out from factory? I know plohls car was way out even on factory tires, read way to fast. Almost as if the speedo drive was for an adm 220km/h speedo rather then the Jdm 180.

Would be a shame to get the right ratio change based on the diff and it still be inaccurate!