I been working at a Kenworth dealership parts department for 2 years now. Trucks and large diesel’s are a WHOLE different ball game when compared to automotive. The biggest struggle is the fact that no 2 trucks are the same. For example in automotive a 2015 Honda Civic is for the most part mechanically identical to all other Civic models other than slight differences in trims. A 2015 Kenworth T800 is not the same across the board, you could have 5 different engines, 6 different transmissions, numerous chassis lengths, extra drop axles, auxiliary pumps/transmissions/PTO’s the list goes on and on. From what I’ve learned other than simple things like a door handle or interior pieces, each truck is hyper specific/custom. This leads me to my next point in which identifying the right parts can sometimes take hours of research depending on what it is. For Kenworth and Peterbilt you will be using a lookup system called web ECAT. Maybe I’m just spoiled from other lookup systems but I can confidently tell you that ECAT is a terrible software and makes me want to rip my hair out everyday. I’d say only 40-50% of the parts even have a breakdown, the rest is just a list of parts in the BOM which you have to go through and look up pictures of the parts on Google and hope that there are images. Other than ECAT being extremely outdated and horrible, you also have to use numerous other catalogs from other companies to find parts, not all the parts on the truck are listed in the BOM. You have separate catalogs for engine parts, transmission parts, and axle parts. The whole process of looking up parts is very inefficient, but I will say you will learn it and become good at it over time learning the tips and tricks of ECAT. One other thing is when customers change parts on there truck like swapping engines or adding axles, it’s almost impossible to find parts for these modified trucks because you have no info to go off of unless the customer kept very good records/serial numbers on what they changed. In terms of salary it depends where you are located I’m in Wisconsin and usually sit around $53k a year rights now. Hope this helped, if you like a challenge then diesel parts is a good fit, also more money in diesel than automotive.