78's used a 1310 at the pinion, 79's went to 1330 series. Many times these vehicles have had swaps done over the years. With so many options for the 9" it's very iffy to guess at which U-joint IS in there, I can tell you which one should be there, and if you give me the needed specs I can tell you what spicer joint would replace it. My 78 Bronco
Keeping in mind I am only stating what was on the books as specified for a particular year, and drive line combo and that mother Ford has a reputation of instaling what ever is at hand and who knows what has been swaped on a vehicle you bought used.
1978 Broncos came with one of three different rear drive shafts depending on drive train 1310 series on both ends unless equiped with the 400 eng, then it was 1310/1330
1979 Broncos came with one of three different rear drive shafts depending on drive train but all used 1330 series joints at both ends EXCEPT when equiped with a 351M/auto trans/NP205, then it was 1310/1330 5-153x (1310) at the pinion and 2ea 5-278x (1330)at the TC.
I fully admit this is all book data, and what is under your bronco may differ, but for what it is worth there it is.
A forum community dedicated to custom off-road vehicle owners and enthusiasts. Come join the discussion about trail reports, builds, performance, modifications, classifieds, troubleshooting, fabrication, drivetrain, and more!