X-Posted from the 251 fourm...

Hi everyone,

I have an extremely well optioned R500 – I purchased it a few months ago. Initially I was really enjoying the car (van, whatever) – but noticed some jerking downshifts from 4-3. 3-2. I continued to drive until it stranded me about 110 miles from home... I took the van to Mercedes and they explained that they wouldn't dive into a transmission but suspected K1 clutch assembly.
So, I towed it back home, and took it to a transmission shop, who told me to get a used transmission with low miles. So, I did. I found a 79k transmission on ebay for $1800. For those unaware, the R500 uses a 722.901 4matic, which seems to be the rarest model of the 722.9 transmission, only shared between the R500 and ML500.

I have the new transmission installed ($1000) – and noticed some flaring. I took the van to a Euro shop here in town who did shift adaptation training which alleviated the flaring. They also performed a positive pressure flush on the transmission (which I think was a mistake). So, now the van has a working transmission with only 70k miles on it. Sweet.... I take it to GA (about 1500 miles from me) and back without any issue. The euro shop also installs a new conductor plate (VGS3).
On a subsequent trip, the van exhibits the _same exact issue_ as before the transmission swap. Just reving. Refusing to put myself on a tow truck once again, I'm determined to get home. I use the paddle shifters and get the van to 6-7 gear (bypassing K1 gears 3-4-5). I make it home.

At this point I'm thinking: the positive pressure flush took any flakes / whatever and pushed them into the valve body. OK. I have the old valve body from the original transmission. I disassemble it, clean it, and torque everything to spec. I bring the car to the transmission shop (where the transmission was installed) and explain my theory. I explain that I'd like them to install the old (now cleaned) valve body because the one that's attached to the car is likely contaminated (codes read: hydraulic fault). They agree to do the work, and call me the next morning at 9am. I'm thrilled, wow, a quick turn around.

WRONG! They broke the conductor plate. Ouch. I explained that the part was very expensive ($2800 after tax tag and title). They agreed to have it repaired. I found a repair service, and they paid for the repair. After they received it back, they installed it along with the old cleaned valve body.

The transmission is not happy. Now I see P2037-004 1936 (Current and Historic No CAN Message Was Received From Control Unit Y3/8n4 (Fully INtegrated transmission Control VGS) Control Unit).

F me!

I'm still willing to invest in this car, but I'm nearing the end of my rope. The second transmission came from a junk yard, who refuses to honor the warranty because "I opened the transmission" (to install my conductor plate, which must happen).

Anyone have a transmission shop that they recommend, or have a 722.901 transmission for sale? =)