I have two angle drives to choose from as I put an XC70 back together. Both seem to have smooth operation and very little play. One rotates more freely than the other and seems drier, maybe. The lubricant is rusty brown. The other rotates with noticeable drag, but seems wetter and its lubricant is deep brown.

I'm leaning toward the wetter, more drag unit. What else should I do in comparison? Should I crack them open and have a look at the gearsets?

 

I'm going with the "wetter" one - replacing all the seals.