I have a 99 F-550 crew with 115,000, 7.3 I believe it has 4:88 ratio and it gets kinda shitty mpg was wondering if they made a 4:11 for the F-550???

 

Anybody?

 

Copied from another forum:

Here are the Dana/Spicer part numbers for the matched ring and pinion sets on the ratios requested:

3.91 Ratio Ring & Pinion Set: 360KG105-X

4.10 Ratio Ring & Pinion Set: 360KG106-X


An important HOWEVER:

Since both the 3.91 and the 4.10 ratios fall outside of the 4.88 - 5.38 range of ratios the stock differential case uses in both diesel and gas configurations, a different differential case will also be required to use the taller gears. (By "case" I do not mean the external housing, but the internal differential case, ring gear backing plate, and bolt group.)

The Dana/Spicer part number for the differential case group appropriate for the range of axle ratios from 3.91 to 4.44 is:

360KQ102-X