speedometer gear
Record Breaker
Joined: Feb 2010
Posts: 1,504
Likes: 1
From: Chesapeake, VA
hi awhile ago i changed my gears from 3.55s to 4.56s and from 265/75r16s to 37x12.5r17 so few years ago when i did that i did not know u could just change the speedo gear so i bought this stupid electric modulator to change the signal to the speedo and its never worked well the speedo changes depending on temp and voltage so i want to change the speedo gear and i can not seem to find a chart with the same numbers on it i find some with 35 teeth gears fit my application then i find other charts that say 32 teeth is for me so was just wondering where i can look i already bought a 35 tooth one and the speedo seems to read way to slow the factory gear is a 30 tooth and i got a spare 36 tooth laying around any advice would be great
Champion
Joined: Apr 2007
Posts: 2,831
Likes: 1
From: Miami, Fl
Not to thread jack but i went from the stock 245/75/16's to 285/75/16's, could you tell me what tooth gear I have and which one I need to correct speedo, its not off far but my dad wants it corrected
Record Breaker
Joined: Nov 2005
Posts: 1,827
Likes: 3
From: Ontario Canada
245 were the stock wheels Id guess you would have a 33 tooth
Maybe 29 tooth speedo gear with the 33s(if 3.55 diff)
Guessing on both
BTW, thanks Scott, missed that.
While Id love to get rear disc I have to draw the line somewhere.
Maybe 29 tooth speedo gear with the 33s(if 3.55 diff)
Guessing on both
BTW, thanks Scott, missed that.
While Id love to get rear disc I have to draw the line somewhere.
Thread Starter
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Veteran
Joined: Mar 2006
Posts: 342
Likes: 1
From: Westmont IL
its easy to pull the speedo sensor to check the gear number the gear says what number it is its a 9/16ths bolt as i remember on the left side of the tail shaft of the tcase took me 5 min to change the gear out and indy didnt the last year of our style rams have optional disc brakes
Banned
Joined: Jul 2010
Posts: 123
Likes: 1
My Indy came with 3.55grs stock & 275/60/17 tires on it & had 32 tooth speedo gear.
I swapped to 35 tooth speedo when i added 3.92grs.
Did your truck come with 265tires factory?
Makes sense having the 30 tooth gear for that 31.5" tall tire so the speedo would be accurate.
37" tires with 4.56 I thought worked out to 3.90 final.(used DML's tire calc)
35 tooth should be very close to accurate
http://www.dakota-truck.net/TIRECALC/tirecalc.html
I swapped to 35 tooth speedo when i added 3.92grs.
Did your truck come with 265tires factory?
Makes sense having the 30 tooth gear for that 31.5" tall tire so the speedo would be accurate.
37" tires with 4.56 I thought worked out to 3.90 final.(used DML's tire calc)
35 tooth should be very close to accurate
http://www.dakota-truck.net/TIRECALC/tirecalc.html
http://www.tciauto.com/Pages/418/calculators.aspx