I have a live axle F-series diff with a 3.9 ratio.
I have an IRS F-series diff with a 3.5 ratio.
I would like to fit the 3.5 ratio to my existing diff.
I have been told that it should just go straight in.
I have been told that the pinion is different on the IRS but that you can do something to make it work.
I have also been told that there's no way it will ever work.
Does anyone know if it can be done, or what needs to be done?
Do you even have to change the pinion if you change the ratio - or can you just have them lapped together?