tire air pressure for 96 chevy truck?

[dee]

I have a 96 ck chevy truck. I have no stickers that tell me the proper air pressure. I got 245/75/16 on truck. My two front tires are new goodyear trackor 2 which calls for a psi of 44 max. my rear ones are used ones that call for 35 psi max. I went to gas station to have them air up tires an they used the max on all 4 tires. I found the front end ran rough(so I dropped them down to 35 psi cause a chevy dealer said I should only have them at 35. But they look low. What do I have the air at in my tires since the 2 front ones an 2 back ones have different psi. I cant afford 2 new back tires now. I dont want to ruin my front ones. Shouldnt the air pressure be the same in all 4 tires. WHat do I use for air pressure? My son told me to go by the tire not the truck. That does make sense to me cause if your tire is under or over inflated it could ruin the tires. Help Please