I am no mechanic but.....I do need help
 

I have a problem and need some advice...I brought my truck in to get the brakes looked at because there was some vibration when stopping. They looked at it and found two things 1) Back right drum was to tight (causing vibration). This was easy to fix, not a big deal. 2) While taking the back tire off they saw fluid on the differential. He touched it and it was wet, then he said it may be a leak and come to find out the plug was not tight.He reached in and felt that there was still fluid in and told me that it should be ok. He filled it and tightend the plug. Well today I looked under the truck and it is still leaking. What do I need to do? How much is differential service? Sorry for the longpost, but if it's not electrical I am mechanically stupid :D. Any help is much appreciated.

2005 CrewCab z71 LT 5.3

RE: I am no mechanic but.....
 

well its eay to tell the fluid will be coming out of the pinion seal or the diff cover it easy to tell just follow the trail up to it the diff cover s real easy losen the bolts, take off cover clean and put rtv around it. the pinion seal is easy (im also a gm tech) it should cost that much to have fixed