722.6 2-1 Downshifting Immediately After a Smooth Stop

[Dekkaaa]

I'm trying to get a distinct sound when shifting from 2nd to 1st gear in my 2011 Viano W639 with an OM651 engine and a 722.6 transmission.

The main problem is a noticeable jolt/shock only when coasting from 2nd to 1st gear, especially when braking gently before stopping. Sometimes there's also a slight hesitation/hesitancy at low speeds before stopping. Harder braking usually makes this less noticeable.

What I've already done:

• Changed the ATF and filter using 236.14
• Replaced the control board
• Replaced the coupling sleeve/plug
• Replaced the pressure solenoids
• Tried a different valve block
• Checked/adapted using XENTRY

Current situation:

• Overall, the gearbox is working much better
• But the "2 to 1" effect is still present

The adaptation values don't look extreme, and I'm trying to figure out what's more likely:

• Related to B1/K1/Freewheel 1
• Related to 1-2/4-5 shift solenoid
• A knock in the transmission caused by a loose drive shaft or mounting, which makes the ride quality worse

Has anyone else experienced a very similar clicking sound when switching from 2 to 1 on the 722.6 model after ruling out common issues with the conductor plate, socket, or pressure? What ultimately helped resolve the problem?

 

[zmzaro]

I encountered this problem three years ago. I tried resetting the adaptation and transferring it using XENTRY, but nothing changed. I eventually read the adaptation from another similar car using Vediamo and transferred it to mine, after which gear shifting became perfect.

 

[weryo]

Please check the driveshaft - Vito models often have problems with it!

 

[Dekkaaa]

I am also experiencing RPM fluctuations at speeds of around 70-80 km/h. I suspect that the torque converter is the cause of all these problems.

 

[r66r66]

The problem could lie in the torque converter, but, honestly, after changing the fluid, you would have noticed an improvement - or at least some difference. In my view - and here I agree with weryo - the issue might not be with the transmission itself, but rather with the driveshaft joints.

Check one more thing. I’m not sure how it works on the Sprinter, but many vehicles equipped with the 722.6 series transmission feature a "winter mode" switch. In this mode, the transmission holds second gear and does not engage first gear at all. See if a similar effect occurs while braking, just before coming to a complete stop.

 

[Dekkaaa]

I do not believe the problem lies with the driveshaft, as I am experiencing a whole range of symptoms. There is one other point worth mentioning: when the kickdown engages, there is a noticeable jolt. If the transmission shifts directly from 5th gear to 3rd, this impact is accompanied by a distinct clunk. However, this does not happen every time. I still suspect a fault in the torque converter, specifically due to the engine RPM surges that occur while driving at a steady speed of 70 km/h.

 

[r66r66]

If the issue lies with the torque converter, there is no choice but to disassemble and repair it (buying a new one likely makes no financial sense).
However, in my view, if the issue lay with the torque converter, changing the fluid would have yielded a noticeable improvement - especially if the old fluid had already accumulated significant mileage. Moreover, were the problem indeed rooted in the torque converter, it would recur time and again.
However, if the RPM fluctuates while driving at a constant speed, there is no need to look for another cause (though I assume you will check the universal joints, as well as the transmission and engine mounts, anyway).
I had an interesting case, albeit involving a 722.9 transmission, where a gearbox fault was suspected, but it turned out the engine mounts were broken. The entire powertrain was shifting, creating an effect similar to "slippage" within the transmission.

 

[Selectronic]

Simply perform the shift adaptation procedure - from the highest gear down to first. Everything required to do this is available in XENTRY. You need to drive out onto an open stretch of road, wait for the transmission to shift into its highest gear, and then allow the vehicle to decelerate and downshift on its own, without pressing the brake pedal. You may apply the brakes gently only once 2nd gear engages, in order to slow down smoothly all the way to 1st gear. Perform this procedure 5 times, and everything will be in order.

 

[Dekkaaa]

I’m going to take the car to a specialized shop to have a full diagnostic and transmission repair performed, including the torque converter. I’ll let you know as soon as everything is ready. I’m fed up with these endless attempts to fix this transmission, which end in failure time and time again. Thanks a lot to everyone for the help!