Differential gear change question

[GregWilson]

I have an 03 Ram 2500 QC with RE48 automatic transmission. I have just changed my differential gearing from 3. 73 to 4. 10 because I'm towing a large trailer. I made an appointment to get the computer calibrated for the new gears. After the gears where changed the speedometer seemed to be pretty close. The RPMs were up a couple of hundred RPMs at 60mph than they were with the old gears and the GPS was reading within 1mph of what the speedometer said. So took it into my local dodge to have it calibrated anyways. After the dodge dealer got through with it. I now have about a seven mile an hour difference from my speedometer and GPS. The speedometer has the higher reading. Also when the speedometer is reading 60mph my RPMs are the same as with the 3. 73 gears. My question is did I need to have the computer calibrated for the new gears or did my local dodge dealer take for for $150. 00. They said they would fix it today if they are capable. I have my doubts.



Thank you in advance for your input.



Greg

 

[AH64ID]

They ripped you off, and messed your truck up.



The new trucks use wheel speed sensors for speed detection, so gearing doesn't play a role. They should have known this as trucks are programmed with the tire rev/mile, and not gear ratio.



I would go get your money back, and have them put it back to how it was.

 

[GregWilson]

That was my suspicion. thanks for the response. They are supposed to fix it today. I'll see what happens and post it here.

 

[GregWilson]

Does anyone a good place to get my speedometer recalibrated. My local dodge dealer of Bellevue, Wa has no clue. I gave them a chance to reset it back to the old setting and they made it worse. Thanks in advance.

Greg

 

[GregWilson]

Does anyone a good place to get my speedometer recalibrated. My local dodge dealer of Bellevue, Wa has no clue. I gave them a chance to reset it back to the old setting and they made it worse. Thanks in advance.



Greg

 

[Prairie Dog]

Mine was off about 4 MPH with stock tires when I checked it against GPS. I got it to within 1 mph with a Smarty Jr.

 

[Motorhead]

Find someone with a Smarty and you can set it yourself. My friend did the 4:10 to 3:54 on a 2002 second gen truck. We reset NOTHING. As AH64ID said, it runs off of the ring gear revolutions and then corresponds to your tire size. A3:73 or 4:10 ring gear still turns one rev to the tire one rev.

 

[orhusky]

Hey Greg, I am interested in doing the same swap. Did you find someone to swap with or did you have to buy new gears. What did the job end up costing you??? Are you glad you did it? We tow a big 5th wheel and would sure like the lower gearing.

 

[Prairie Dog]

Sounds spendy - us 4x4 guys have to pay for two sets of gears!

I've had very mixed results from Dodge of Bellevue. They scratched my dash and chipped the paint off the edge of my door (argued and then fixed both) but they also replaced my defective steering gear that Dodge of Monroe lied and told me was good.

 

[AEdelheit]

Smartys work great, can dial it in extremely accurately, I have one for sale if your interested.

 

[mpaulson]

My local dealer was planning to calibrate the speedo when they did my gear change from 3. 73 to 4. 56 until I taught them a little about the trucks that they work on and explained that they don't need to also?? Nice to know that the dealers really know there stuff!

Confidence inspiring isn't it?