If I change the differentials do I have to change the t-case?
By "differentials" do you mean the whole front or rear end or just the "ring & pinion gears"? The answer is NO assuming the overall sizes & locations don't change.
The whole front and rear ends
Still NO, & if the ratios are the same.
Looking for a Used Eagle in your area?
CarGurus has 2 nationwide Eagle listings and the tools to find you a great deal.
Search AMC Eagle Questions
AMC Eagle Experts