Underneath the E36 (all models except ti compacts) there are two black plastic trim pieces found just behind the rear jack pads, in front of the rear wheels. These trim panels fill an oddly shaped gap between the plastic fuel tank and the rocker panel / cabin floor. They also have a small air dam protruding straight down to help funnel air around the rear tires. The M Coupe has something very similar in the same location. And just like on the M Coupe, this flimsy little piece of plastic is the first item to get damaged during any off track excursions.
The photo below (sorry for the poor quality) shows the right side trim panel, which had suffered a torn mounting tab. This allowed it to flap about, doing little to control the air flow underneath. The following photo shows the broken tab and the new panel.
These panels are held in place by a 10mm stamped washer/nut at the front and an 8mm screw at the rear and further secured by being sandwiched between the fuel tank and chassis.
It’s a very simple job, the hardest part is actually finding the part numbers for these two pieces. It took a lot of digging on RealOEM before I was able to narrow down the proper pieces. Hopefully this saves someone the trouble.
All E36 Models (Coupe, Convertible, Sedan, M3) exc 318ti Compact:
TRIM PANEL LEFT: 51718130071
TRIM PANEL RIGHT: 51718130072
at 16:18
Thanks a lot for this info! Very useful.