Surfing the b2 piston issue and its now also possibly the valve body at fault
 

http://www.peachparts.com/shopforum/diesel-discussion/385196-valve-body.html
The above link was a thread started back in april of this yr and connects this issue as a good indicator to other possible transmission culpriepts when it comes to examining the olde no forward gears but reverse gear still working scenerio .Rollguy after extensive issues also found this through his transmission shop.http://www.peachparts.com/shopforum/diesel-discussion/385909-300td-b2-piston-replaced-still-no-forward-movement.html

Cleaning the valve body is almost free. The cost is your time, a trans filter and fluid. It might take you the better part of a day to remove it, clean it and reinstall it. When cleaning it, be comfortable, clean and take your time. You probably already watched my YouTube video on this but if not, here it is:

https://www.youtube.com/watch?v=h9thWDLR5yo

Yes ,your video is very well recieved by everyone that goes for a view ,the time you spent making it is very informative ,thank you .I Do have a few ???When you drop down the valve body do any sm. parts need to be watched for, i know when you crack them open its all eyes on ? I can see the improvement in shifting would enhance alot of older trans behaviors if a kit is installed in the upper VB .Do you offer this as a service ?,just curious.Do trans shops deal with just valve bodies ,an in and out kind of exchange.

The valve body is really like the brain of the transmission ,hydraulic brain .The newer generations of transmissions will be electronic gizmos since the future of cars require more gears and better performance,a time we live in and may not be DIYable .The electrical engineering is very interesting in this new part of the newer car models , a diagnostic port is the future in the hydraulic mechanical vehicle world .The H fluid flow and its controls will be enhanced and complicated sealed pieces ,dealers will want it that way ,already alot have put this forward , VB s of the future.

Ill break the VB open but need alternative steps if it goes wrong ,always a backup plan in my case.Some reasearch done and a few steps yet to do till I submitt to the VB being the issue,the b2 piston needs to be checked out ,the things I have checked on about the VB are looking very promissing though , finding someone who warranties the part has been found .Ive inspected the trannie pan for any debree,it has the normal grey thin silt at the very bottom of the pan that Ive always found after these steps of, inspecting ,replacing filter and refilling,nothing out of the ordinary .I hate to open up the B2 piston and all its steps till I get it in a garage,check it then start after the vb..Still hesitant on dropping the valve body for the same reason.Im religious about service on any daily driver Ive owned jn the past ,this at once a yr service.A good T Rebuilder shop has a VB on the shelf,just havent a price yet .All the other surrounding T shops use them on Mercedes Trannies and VB related issues so Ive got some confidence that the VB will be worth it .Ill pay $500 or less ,only if I know for sure its my issue.Im hoping to have them look at mine to save a step first to verify a complete clogged VB and this while I watch to take photos for this post .I can then go to take the new VB for reinstall with a better feeling after spending that kind of cash.Its a 722.315.If it doesnt go as Im hoping I have a good matching working trannie sitting in the wings,just not rebuilt ,Ill put the VB in it and go for the reinstall with some new seals.Still working the problem .

http://www.jaggiimport.com/about.html
It turns out he does full trannie rebuilds but for shops only.He will supply serviced VBs to the public,pretty resonable at $225 .with exchange ,youll need to give him a number off the vb and he can ship direct.

Did you inspect your b2 detent valve and shift valve when you had your pan off?

Do this with compressed air? I was told by a trannie guy who knew how to check the b2 piston once the pan was off but he got side tracked before he could tell me where to look and what his process intales.A site with exploded view of trannie I found
https://nemiga.com/cat_spares/epc/mercedes/1/ga/722315/08S/27/001/

Happy new year my thoughts were just to pull the valves check springs, seals and ease of movement.

Waiting to get it towed at the moment , Ill soon have it on concrete with real tools to tackle the b2 piston and its inspection.It might require the VB look ,next step if the B2 piston doesnt pan out for the issue.AN RHunter revisited THREAD wrote of a service requirment if never accomplished ,a real problem area for the 722.315 trannie in its service history by Mercedes.OH Yes ,Happy New Year .

A new helpful link
https://brandon314.files.wordpress.com/2011/09/tranny_722_mitchell.pdf

Sorry, I have been away from this site for a while. My apologies. Did you ever get a pressure reading from the trans? I find it helpful to know if you have a good baseline.

There aren't really any surprises pulling the VBs off. Clean both VBs like in the video. If you do not have a replacement gasket, be gingerly taking the assemblies out. Sometimes the old gasket will get fused.

Rebuilding one of these transmissions is not that difficult if it comes down to it. Eventually, I'll make a video of that.

Moving alot of stuff around and this seems to be on the backburner for right now.3 wks Ill be back at it.