Are you looking for a speedo gear but prices are high?/Gear calculating info

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Dusterdude72

Dusterdude72

IN MOPAR MUSCLE MAGAZINE
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well I did a bunch of looking around for a speedo gear over the last few weeks (I have a 28 inch tall tire and 4.56 gears which calls for a 43 tooth gear) and year one wanted $89.00 plus shipping for it and I couldnt find the size I wanted on ebay and I called the stealership and they told me it was going to cost me $115.00 plus tax!!! (for a little medal bar with a hunk of plastic on it....are you serious? HA)

any how.....I finally checked out randys ring and pinion and found the gear I needed ,brand new for only $15.00 !

the shipping was a little pricey at $15.00 (total of $30.00 shipped to my door) and it took about 6 days to arrive.

BUT compared to what other places were asking for the same thing......$30.00 sounded like a heck of a deal.

the gear arrived and looks great!.

I figured I would pass it along to anyone else who might be looking for a speedo for the setup they have and found that the gear they need is on the pricey side.

here is a link to the gears http://www.ringpinion.com/Search_Re...Price&SearchType=Key&SearchPhrase=speedo+gear
 
Wow! Can't belive they went up that much at the dealership.
I bought one at the local dealer about 3 years ago. I think
it only cost about 7-9 bucks.
Thats insane!
I have a few used ones, I'll hang on to them.
 
Thanks for the heads up. I always pull them out whenever I see a Mopar trans at a junkyard.
 
Wow, I must have the wrong chart mine says 28" tire and 4.56 should be a 40 tooth orange gear.
 
hmmmm.....not sure about that chart, I ran through a few different gear calculators and went through the factory part numbers and the superseded part numbers and all and it all shows a 43 tooth gear is what was called for.

here is yearones chart (look at 27.9 tire x 4.5 gear range=43 gear)
http://www.yearone.com/yodnn/tech/T...Q/MoparSpeedoGearChart/tabid/415/Default.aspx

and another http://home.earthlink.net/~mopared/speedo.htm

and even mymopar.com says its the correct gear. http://www.mymopar.com/speedometer.htm

and in my yearone mopar parts catalog they have a speedometer gear chart and it says the same. this is all up to date info

here is a mathematical break down of it

first off , 275/25.4 =roughly 10.82
10.82x60%= 6.5
6.5x2=13
13+15=28" tire diameter
this tire would have 720 revs per mile

the formula for the speedo gear being 13(drive teeth)x4.56(rear gear ratio)x720(tire revs per mile)/1000= 42.6816 (43 tooth speedo gear)

here is an example of how to come to this conclusion that I worked up

727 Push Button = 8 Drive Teeth
727 Non Push Button = 13 Drive Teeth
904 Non Push Button = 13 Drive Teeth
--------------------------------------------
Drive Teeth x Rear End Gear Ratio x Tire Revolutions Per Mile/
1001 = Gear Teeth
--------------------------------------------
Tire Revolutions Per Mile quick guide

24” = 840.3 Tire Revs Per Mile
25” = 806.7 Tire Revs Per Mile
26” = 775.7 Tire Revs Per Mile
27” = 746.9 Tire Revs Per Mile
28” = 720.3 Tire Revs Per Mile
29” = 695.4 Tire Revs Per Mile
30” = 672.3 Tire Revs Per Mile
 
Hope that clears up any confusion on the conflicting info between sources:toothy8:
 
Thanks for the post Tony, I just seen that chart somewhere here on fabo recently and I was looking for it to post to this thread but could not find it.
 
Well one day I will get the correct speedo gear for my Duster. I usually drive by tach. I know 4,000 rpm is 70 mph (I checked it by my GPS)....when I cross the stripe at the track at 5,600 rpm that is 105 mph. LOL.
 
Yup, it's amazing how info changes from place to place. At least the gear I ordered for mine is correct on all of these charts, whew. Thanks Tony for the chart, I saved that one too.
 
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