Originally Posted by willwren
The Diff and sun gear are not different between the 2.84 and 3.06. The difference is INSIDE the trans. The drive and driven gear on the final drive are different ratios.
This is incorrect. Go look at an ATSG manual..
To get a 2.84 FDR it takes a 35/35 gear set multiplied by a 2.84 diff.
To get a 3.06 FDR it takes a 35/35 gear set multiplied by a 3.06 diff.
To get a 2.97 FDR it takes a 37/33 gear set multiplied by a 3.33 diff.
The list of combos goes on..
As long as you have a 35/35 gear set (which a 2.84 would) you can bump up to a 3.06 or a 3.33. You just need the diff and sun gear from a trans with the gear ratio you want.
If you want to get real specific.. You really only have to change the sun gear and the spider gears in the diff. But there’* no real point to that unless the side gears are messed up.