Rear end gears and speedo

Rich · #1 (**permalink**) 04-07-2002, 07:27 PM

Now that I've changed rear end gears (2:88 to 3:56), I'm assuming the speedo is reading fast...right? The tranny is a World Class T-5. Does someone make an adapter or something to compensate for different gear ratio?

Rich

Back in Black · #2 (**permalink**) 04-07-2002, 09:00 PM

I am right in the gauge selection/aquisition process for my West Coast, so this is timely for me.

Some gauge manufacturers offer a gear reduction/increase kit for the sender portion. Check with your gauge maker to see what they have...maybe they have a table/chart to help you sort out which one you need...otherwise, you have only the option of going with an alternate electrical programmable speedo, or living with what you have, learning the true vs indicated speed

427sharpe · #3 (**permalink**) 04-08-2002, 01:50 AM

Do it the easy way! You changed from 2.88 to 3.56, and I assume you didn't change tires. divide 3.56 by 2.88 (1.236). Pull your speedo gear, count the number of teeth and multiply by 1.236 and go to Ford and spend 3 bucks on the new gear, pop it in and drive off! So, if you have 15 teeth on the gear you have now (and it was correct at 60 mpoh with the old gears, yes??) go to a Ford dealer and get a gear with 19 teeth (round up to avoid tickets!!). Bada Boom, Bada bing your done (sorry, I just watched The Soprano's!).

Jack21 · #4 (**permalink**) 04-08-2002, 05:32 PM

Your FMS catalog should have a speedo drive gear selection chart. Think the gear you want is the "Black" gear.

If you have a mechanical speedo, and you're still off, you can use a reduction gear device in your speedo cable to adjust. Will look up phone/website if you need one.

Newer speedos calibrate electronically.