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new gears, speedometer is screwed

1K views 10 replies 5 participants last post by  DudleyDodge 
#1 ·
I just got my 4.56 gears installed today. Expensive, but it was money well spent. Anyone out there with 35's or bigger and stock gears, take my word for it, its so much easier and so much more fun to drive that you don't have to coast up hills and baby it away from stoplights. Now I need to know the best way to correct the speedometer. A lot of people talk about the superlift signal modifier, can anyone quote me a price. I also understand that on 97's and older I can change the gear drive in the rearend. If so how, where do I get the new gear, and how does it go in. I plan on having 38's within a month, but if the gear is cheap I don't mind changing it twice. The superlift thing is nice and easy but how much $ ?
 
#2 ·
Rocky Mountain Suspension Products has it for $163 but they charge shipping. 4 Wheel Parts Wholesale has it for $183 and they don't. Call 4wpw and get them to price match. :wink:
With the 4.56's what rpm's are you turning now in overdrive at 65mph? I'm trying to decide weather to go with 4.11 or 4.56?
 
#3 ·
On 2002-01-12 01:06, ruffram wrote:
I just got my 4.56 gears installed today. Expensive, but it was money well spent. Anyone out there with 35's or bigger and stock gears, take my word for it, its so much easier and so much more fun to drive that you don't have to coast up hills and baby it away from stoplights. Now I need to know the best way to correct the speedometer. A lot of people talk about the superlift signal modifier, can anyone quote me a price. I also understand that on 97's and older I can change the gear drive in the rearend. If so how, where do I get the new gear, and how does it go in. I plan on having 38's within a month, but if the gear is cheap I don't mind changing it twice. The superlift thing is nice and easy but how much $ ?

you can get the gears from the dealer. there is a thing on the dodgeram.org website about modifying the cab to pcm signal with just a resisitor. basically the only thing that the truspeed does is change a frequency to the pcm to correct it. thats why you turn a pot adjuster. the same can be done with a resistor but figuring out the correct ohm i think would be the tought part.
 
#5 ·
To demontweak, I don't really know what rpms I'm tunrning at 65 b/c I don't know when I am going 65. I also don't know how far off it is. I just got the truck back Friday, I haven't had a chance to drive next to someone for a rough calibration. If you don't know what gears to go with, if you are going with 35s or bigger, in my opinion you need 4.56s. If you drive mainly on the highway at cruising speed 4.10s would give better mileage but I don't know how easy they would turn over. 75% of my driving is in city traffic or 4 wheeling. Odd mix I know, but such is the life of a college student.
 
#6 ·
I recommend the Superlift Speedometer calibrator. It will allow you infinite adjustment for whatever size tires you choose.
I have a 97'. It has the speedometer gear and the VSS(vehicle speed sensor). I could have gone either way but chose the speedometer calibrator over the gear.
 
#7 ·
Oh yeah I forgot. If you plan to run 38's, they don't make a speedometer gear that will get you very close. I checked into getting a gear for my 36's. I understand that they only make the gears for tire sizes that were available on the truck as options. That's why I chose the calibrator.
 
#8 ·
While you were waiting to egt the speedo calibrated, go 60 mph for one mile. When you get the time take that number and divide it by 60 and that should tell you how fast you are actually going.....I think thats how it goes.
 
#9 ·
Just to be sure, does that gear for 38's include the fact that I have 4.56 gears? Also, can my dodge dealer tell me what gear I need, or do I have to know ahead of time. If you have or can get that part number I would appreciate it. I would like to have the calibarator, but I am saving for a 5 inch skyjacker and every hundred bucks helps.
 
#10 ·
I talked to my Dodge dealer today and they said to count the number of teeth on the gear now and that for every tooth gained or lost would change the speed about 3 or 4 mph.
Can anyone confirm or deny that statement?
 
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