Ok I need some help. I had 4.10 mopar gears and install kit from Moe's installed back in October by a local shop. Well on Wednesday I had them fix a diff cover leak. Drove the truck home and maybe drove it for 30 miles the next day. Here's the problem. Last night we were headed to San Diego from the Phoenix area with our travel trailer which is well under the tow rating of this truck and I got about 160 miles from home and got flagged down by another motorist for a bad smell. I limped it to the rest stop just up the road and the rear end was smoking and just stunk like burnt oil. After a very long wait I had the truck and trailer towed all the way home along with me and my 4 other family members. I checked the fluid just now and it isn't low. My question is, could the shop have not added friction modifier? Would that have caused me to smoke a bearing or even the wrong fluid? I have driven this setup for close to 20k miles and have taken my trailer to California, northern AZ a few times and all the way to Yellowstone and back with no issues.