Is there a difference between a rear Drive shaft u-joint for a Dana 44 vs 30? Size, diameter or otherwise?
The Spicer 5-785x is no longer available, it was superseded by the 5-1310x around 5 years ago. I agree with the recommendations to avoid the weaker greasable 5-153x and go with the stronger and more durable sealed 5-1310x.For the stock driveshafts there are 3 u-joints in the front and 2 u-joints in the rear.
They're all 1310 series u-joints and the Spicer p/n is 5-785x. You can go with the greasable 5-153x but unless you regularly do deep mud, the 5-785x is triple-sealed and is a more durable u-joint without the need to be regularly lubed like the unsealed 5-153x.
The Spicer 5-785x is no longer available, it was superseded by the 5-1310x around 5 years ago.