I have a 2005 Quad with the 4.7. It had a 3.55 axle gear, and I am getting a 4.10 put in now. I have already upgraged the tires to 265's from the 245's, and my question is the following:

If I take it to the "Dealer" and get them to update the computer to reflect the changes I have made what do they really do?

Do they simply fix the speedometer reading for the tires (I know the axlegear is read correctly anyway); or does the programming change shift points or anything else that is of actual use. If it's just the speedometer I might just live with it, but if it's shift points or more I may go ahead and pay up.

Any idea?

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I just got mine back last week. Still breaking in the gears . I too went from 3.55 to 4.10's. Speedo does not change.I confirmed that with my GPS unit as well.Don't know for sure about the trans. But the 545RFE is fully electronic. I am pretty sure shift points will beset by the computer. So you should not have to do anymodificatiions.Maybe one of the Dodge techs will chime in here on trans issue, but I do not plan any transmission updates. I do run superchip on my 03.
Dan
Sorry. Just reread your post about the tire upgrade. Your speedo should be out about 2mph from the tire switch. I switched from 245 to 265 as well.

 

If you are taking it to the dealer just to recalibrate your speedo it's like 35 bucks, that should be all that you need todo- I went from 265 to a 305 and it was off quite a bit - and is still off by 2-3 (going by my gps).

 

The gears will affect your shifting, but no programming will be needed. The 4.10's will go through the gears faster than the 3.55's, but the trans will still shift at the same rpms as it did before (might notice a little difference because the load on the engine at different speeds will be different because of the gearing advantage). [/align]

 

Im not sure if the dodge runs hte speedo off of a gear in the transmission or from a signal on the abs, but normally if itruns off a gear or signal in the transmission then changing the final gear ratio will change the mphas far as the trans is concerned so that would need to be compensated for as well. As long as I am thinking about it correctly, the transmission will rotate x amount of times and depending on gear will rotate the drive shaft y amount of times. If the computer knows with a certain tire size and final gear ratiothat at a given rpm it will be at a certain mph then when you change of of those 2, or in this case both, it will have to be compensated for by electronic means. Now if its calcuated from the abs sensor on the hubs, everything I said is out the window

 

I'm pretty sure they just pull it off the abs, not the trans or rear end (I know it's not off the rear end). All the service tech does is adjust for the tire size (they should have it but if not go prepared with the revolutions per mile so they can just plug it in)....it's a quick thing and should be < $50

 

On my 03. The ABS/Speed Sensor is located on the top/middle of the rear differential housing. The rear ABS/Speed Senser works off the tone gear located inside the differential.
Dan