Antonio, I have never seen a Breakaway with the 4 speed that didn't have 3.73 rear gears, of course, someone could have ordered it with 4.1 gears BUT, there is an error, small but important, there was never a 4.11 set of Dana 80 gears, they were 4.1, The person that wrote the 4.11 didn't have the correct information. I would be suspect of the hand written photo copy. There should be a tag on the diff that shows the correct ratio, of course if someone changed it, that may be missing or?

The Breakaway brochure, it lists the rear as 3.73.

Breakaway Brochure



The part number is needed to see if the diff case is the correct one for 4.1 gears, as mentioned, there was a cross over case change between gear sets between 3.73 and 4.1, 3.73 gears could be put in the larger case with shims but 4.1 gears could not be put in the 4.1 case with out case mods or not sure if even possible.

Also the chart that I made was for the engine at max RPM, (TOG), = 2800 RPM, Breakaways with 4 speed, 3.73 rear gears and 19.5 tires, should do ~65 MPH @ 2500 RPM in 4th.

Even in my Breakaway with the 230 HP, 4.1 and 6 speed I have always thought that the rear ratio should have been something like a 4.56, but it would be at the expense of fuel economy and engine life.

I believe that Rusty commented before that the Spartan choice of gears were not the best for the Cummins engine, The guys with the 32' and longer Breakaways and the 5.9L engine have a similar issue if they have 22.5" tires, they virtually can't use 6th gear, way to high to be of any value.

It is a drive train "system" and all components have to be evaluated, it is not as simple as it would first appear. Once modifications start, it would go on and on to get everything back in balance.

I think mine is the one in the brochure.