I wish I could remember...

[Ausydad]

I'm trying to remeber where I saw the chart for figuring out the proper tooth speedo drive gear. I've recently went from 2:76 7.5 rear with 195/70/14 to 3:21 8.25 with 275/60/15 (28.0 H) and seems like it reads 90 when I'm just keeping up with highway traffic (65 m.p.h.). Anyone know where the chart is or have the right answer so I can order one??

[gthomas]

Ausydad,

I'm suggesting that you go to tirerack.com and find each tire and look at the specifications, which should list the circumference. I would divide the two and use the percentage obtained to multiply your existing gear to figure out what gear you need to go buy.

I'm assuming that the stock size was probably either a D70-14 or E70-14 tire and with 2:76 gears would most likely use a FD029 (Black 29 tooth) for the speedo. This same size tire using 3:21's would require FD033's. So I'm basing my calculations on this gear.

3% difference = FD032 (Black 32 tooth)
6% difference = FD031 (Green 31 tooth)
9% difference = FD030 (Yellow 30 tooth)


FD###'s are what is listed in the YearOne Catalog, Unfortunately, the YearOne Speedometer Gear Chart that I have, lists F70-15's (215/70R15) as the largest on the chart, your larger size isn't on the chart.

GT

[dkn1997]

The Year One catalog has the chart you are looking for

[ehostler]

Waht you are looking for is in the archives. The link is http://www.moparchat.com/forums/show...threadid=61577

[rumblefish360]

"E", I had a problem with the link to the other board. Perhaps you need to be a member?
Reguardless, the yearone cat. has a chart to help with the most popular sizes. Mostly stock sizes from gear ratios of 2.76 - 4.10's.

[ehostler]

I have fixed the link. They are now a .org instead of a .com

If you look at my very last post, you will see the math on how to determine which speedo pinion you need. The math is based on tire size and gear ratio.