changing gear ratio with tires ?

[PolarisRMK]

I have a 2004. 5 CTD with 3:73 gears and i was woundering if it is possiable to obtain a gear ratio of 3:55 and not affect ride and performance. If so what would i need to do. The reason for this thought is that from my 01 CTD I was getting better fuel MPG with the 3:55 and now with the 3:73 it is not as good could this be the problem? Thank you all for your input.

 

[XJSuperman]

I'm guessing you have the 265 series stock tires? they're 31. 4" tall. You;d probably have near a 3. 55 ratio if you went to a tire that was about 33" tall... the 285 series tires are 33. 1".

 

[Bertram65]

I doubt gears will make much of a difference, if you want the mileage you where getting with '01 you would need to turn down the power on your '04. 5 to match your '01. I have tried running tanks of fuel staying below a certain speed effectivly giving me the RPM I would have with taller gears, makes very little difference. I can run a tank staying at or below 65 on the highway, taking of slow from every light and get 17. 5MPG, or I can run 75 on the highway floor it from every stop light and get 16. 5MPG. I have the 4. 10s so the engine is spinnign pretty good at 75MPH. Power costs fuel even if you do not think you are using it, a motor that makes 325HP will use more fuel even when driven the same as a motor that makes 215HP.

 

[Blakers]

Try to get down between 1800 and 2000 rpm at your normal cruising speed. I personally think rpm is the biggest robber of fuel on a diesel. Especially when that rpm is not needed to pull the load, but is just wasted in too low of gearing.



I had 285s on my 95 Ram with 3. 54 gears, so I'm gonna go to 315s on my 03 with 3. 73 gears. Should be close.



Blake