I had the same issue years ago. I found that the pulley on both alternators were polished smooth by the belts slipping for a long time, just replacing the belts solved the squeal I was getting but would come back about 3 to 4 weeks after. I agree on the belt sizing, there are different size alternator pulleys GM has for that frame so it can be very easy to not have the correct one for our application. If you put too much tension on the belt you will burn up the bearings in the alternator. I finally replaced both pulleys and no more squeal, my thinking was my truck had this issue while in service in the National Guard. I got it from GL doing this. It mostly was happening with the glow plug drawl on power until the voltage leveled back out to 24+. Battery condition also factors in, this I have first hand knowledge of.
Most CUCV's by this time in their life are running on rebuild alternators and rebuilders are looking at voltage and in our requirements, isolated ground. On the pulley part they just grab one for a v-belt. I remember getting one alternator and the pulley was so small I started laughing, the diameter I think was 1-1/2" , I did not think v-belt that size could be bent that tight.
The info here on SS is outstanding. That being said everyone also needs to keep in mind the info in TM's may have errors and do to real life situations with parts, not all the part lists are perfect for your application. Most of the vehicles and other equipment we talk about here is old, **** manufacturers have recalls on the new stuff that got out messed up, only you know exactly what your old iron needs. I use any list as a guide with my research to maintain or repair.
but will pretty much last forever at least in adjustment.
