loss of reverse -automatic transmission
 

I have a '79 W116 300SD. Transmission 722.120 was working correctly(no slippage, no flaring, shift timing also ok) untill I took it to the mechanic to replace the engine).
When he put the new engine in, he found out that reverse was gone but couldn't help me much about fixing it.
Before I go to the mercedes transmission expert, I would like to try to find the problem myself because it's one of the reasons
why I bought this car, to fix as many things as possible myself and learn a few things in the process.
I have already searched this great forum and some other sites and found a lot of helpful information.
My question is: How can I quickly find the problem before taking the whole transmission out.
I know that B3 band could be broken or simply not engaging, some servos and valves stuck, or pressure too low.
It is strange that it happened after just sitting in the
shop and the only thing done to the transmission was to drain the fluid and replenish it after the engine replacement.
I will appreciate any suggestion. Thanks

Make sure it has enough fluid(but not too much!), make sure the shifter lever is tight and working correctly, and you can check vac lines and such too, though I don't think they'd affect reverse. Seems odd that it'd just "go away" when the engine was replaced....something is fishy.

When I brought the car home, I've checked the fluid level and it
was way too high.
I had to drain around 2 quarts to achieve proper level.I suspect
it could have caused the problem.
The shifter lever is connected properly, it clicks in the position but nothing happens, same as in neutral.
I have checked the vacuum lines, control valve and linkage myself. They had to be readjusted. Now the tranny shifts properly
in all forward gears.
I haven't tried B3 adjustment bolt because it is shear-off type and not easily accessible for a backyard mechanic like myself:rolleyes: