Shifter and Linkage

 

Above: Three linkage rods whose purpose is connecting the shifter to the 4 speed manual transmission. 

There has always been quite a bit of slop in the shifter and often when shifting from second to third gear you'd find yourself in a place I called upper third where the shifter seemed to travel farther towards the firewall than should be possible and it felt like all connection to the transmission was lost. Missing a shift in traffic when driving a car that makes about 45hp to the wheels is not acceptable. 

In the eyelets at the end of these shift rods are nylon bushings. Or should I say there should be nylon bushings. One of these bushings was missing from my shift rod and I ended up replacing it along with the others which seemed to correct the upper third problem. Note that there are also 3 rubber bushings on the transmission side of these rods. Mine were in good shape.

Shifter:

Though the upper third problem was resolved it was still difficult to feel the difference between the car being in neutral or being in gear. I removed the console and the four bolts holding down the shifter assembly.

Above is the shifter assembly removed from the vehicle. The photo is from the left side of the assembly. This is the side that would be closest to the outside of you right knee as you drive were you driving in North America. Inserted in the center hole of the assembly is a long spring. The spring is retained by a plug which I've photographed in the below picture. This plug was about to fall out the side of the shifter assembly. The only reason it hadn't done so was because while in the car the plug was pressing up against the inside of the center console.

Above: Deteriorating plug with metal washer.

I discarded the smaller pieces and tried to reinsert the plug. Two things are causing this to fail in my opinion. The first, with pieces broken off, there is no longer the required surface area remaining on the plug to maintain enough friction against the walls of the shifter assembly to retain the spring pressure when the operator moves the shifter to the left. The second, over time the rubber plug has stiffened, and shrunk.
TLDR; Plug is old and won't stay in when shifter is pushed to left.

 Above: Worlds worst cotter pins?

My solution was to drill 4 holes in the plastic housing of the shifter assembly with a Dremel, and insert copper wire to retain the plug. This seems to work on the bench as well as when bolted in the car. Though I haven't actually driven it yet, shifting the car in the garage feels like shifting other cars from the 80's. Which is a huge improvement of what it felt like before. My question is, why didn't Mercedes put a snap ring at the edge of this shifter assembly to retain the plug?

After installing this I found that it will not work. The cotter pins position the spring too far in towards the shift lever. When trying to shift into reverse, the spring becomes fully compressed and the shift lever is unable to move far enough left to slide into the reverse position.