1996 E320 53k KM, 722.509 transmission, suddenly hard shifting
 

My 1996 E320 has 53k km when the transmission started to shift very hard from 1-2-3-4, but not from 4-3-2.

The transmission is 722.509

It did not happen over time.

I drove the car, everything was fine as usual. Parked and turned engine off.
Later that day, had to use the car, started and it had this hard shifting.
I brought it to a shop.
On the bill ($400) was:
Replace valve body piston seal kit
Valve body seal kit
100% ATF replacement

It did not solve the problem at all.

Now they want to overhaul the transmission, lineup etc. I still cannot believe that this is needed after just 53k km.

Strange is, the transmission was 100% perfect and very smooth as I turned off the car. Then after turning on, transmission was bad (must be a ghost playing with the transmission during the time the car was not used).

Note that I am living in the Philippines, here's no Mercedes service. I found a Mercedes mechanics who worked for Mercedes here before, as we had still a Mercedes service here on the island. But I smell that he just want to make some extra money with a maybe simple and cheap repair. And with an overhaul, he would make a lot of money ($1600)...

So, I would be grateful for ANY suggestion about this issue.

Sounds like a vacuum issue with the modulator.

Doubt that trans needs overhaul!

Thank you, thats what I also thought.

Because of lacking service manuals/Mercedes service here, how can a vacuum be tested? The shops here don't even have a gauge (!).
If possible, I would check it myself, but where to start?

Could the EGR or MAF cause this behavior too? Or even the Vaccum modulator valve (I think thats what you meant with vaccum issue with the modulator)?

On the LEFT side of the transmission is the vacuum modulator, with the engine running the plastic line should have vacuum (suction).

If not?? then the line to the intake must be disconnected or broken.

Thanks, will check it.
What if the vacuum line is fine, no cracks, not disconnected?
Could EGR or MAF cause such symptoms?

Try adjusting the bowden cable....I had that problem as well, but I have a 190, wouldn't hurt to try.

Bowden cable was adjust ed already, and shift points are fine.

Can anybody provide me a vacuum diagram which would help me to track all the lines?
Must be for 1996 E320 i6, not v6 if that matters.
I googled for hours without luck.

Update: When it shift with rpm >= 4500-5000, shift is smooth as it once was, cant barely feel it. But with low rpm, shift is very hard.
When accelerating to lets say 4000rpm, then breaking, the transmission shift, and its horrible hard.

And again, it does it only in one direction, from 1-2, 2-3, 3-4, but never from 4-3, 3-2.

Issue fixed.

The vacuum line going to the modulator was squeezed.
This happened as the mechanics installed a new CPS. I must have had the line under the CPS. And even I told him to check this area, he never listened and wanted an overhaul of the transmission.
Today, I wen to another shop. We lifted the car, and the mechanics found right away the squeezed line. Replaced it, and transmission is shifting so smooth that I first thought its not shifting at all :)