what do i set my tire pressure on a drop axle tire

I would go to the tire manufacturer's web site and see what it says.

Just an example

 

Put it at 130 then. Tires are constructed a certain way, and they need a certain air pressure to maintain their shape. Otherwise they run hot. Look at a 14-ply vs 16-ply. Two different air pressure specs. Would you run your 16-ply at 105, just because that's where you run your 14-ply?

 

Tires usually have a range. Like 105 PSI min to 130 PSI maximum depending on the weight load.

 

I'm going to start running all my tires at 80 psi, because that's what I run in my pickup.

 

First problem, they are TA "mechanics".

Bypass their moronic input, it's wasting your time and everyone else's.
Tell them the correct pressure to set it at, which is the pressure for the load your are applying or the max load carrying pressure of 130 psi.

I run all our Energy Z steers and super Singles at 125 ... The morons at TA have tried setting our singles to 105 as well... Derp!

TA guys are parts changers and they do a mediocre job at best doing that. Lol.

 

The proper tire pressure for ANY tire depends on the load it carries. On the manufacturer's website will be a "load table", like the one @Farmtractor9900 posted. Calculate / weigh how much each tire carries, and then look up in the table how much pressure to put in that tire.

I'm always amazed how little tire store employees know about tires.