Volvo E series bus, transmission problem

[kik]

Hello ladies and gents.

I am currently engaged in trying to get my elderly neighbours Volvo E series bus moving.

I am a qualified mechanic with 40 or so years in and out of the trade, so I will be familiar with any terms you may use.

I am not however a diesel mechanic and have very little experience with trucks or buses.

The bus I am currently working on has a semi-automatic transmission and it refuses to go into any gear.
I have removed the access panel to reveal the transmission and I removed the pressure release switch (at least that's what I think it is) to see if
it was getting any air to the master junction box, which revealed that there was no air in that part of the system, there is air for brakes, etc but
when you try and put the bus in gear there is no discernible clunk or any other sounds to which would relate to any engagement of any of the air valves.

When in the bus and it's running you can bring the revs up a little and it does try to move, however it does the same regardless of what gear is selected,
including reverse. My theory is that it is partially in a forward gear and that there is no air pressure getting to any of the valves to either fully engage or
disengage the gears.

Of course I could be way off, which is why I'm here.

I located a electric control box near the main air line and am curious if there is a solenoid or similar that requires a power source to activate it in order
for air to get to the relevant valve box??.

Again I am assuming that this would activate via the release of the handbrake and once the handbrake is disengaged it would in turn activate the valve
body to control the transmission??..

Please feel free to call me silly names if I am way off...as mentioned I am NOT familiar with buses, so this is quite new to me.
I live in a remote area of Victoria and the old fella has sold the bus and now it wont move.
I might also add that he is not very apt in regards to much of anything, and he has been performing some new wiring in the bus and I suspect he may have
inadvertently damaged the wiring that may or may not control the area I am currently looking in.

I have checked the fluid level (did that first) and it appears fine.

As mentioned bus is a Volvo E series with a British Leyland transmission which is marked as follows

BL GB 346/8
GND UR8191
UNIT 5001331

Thank you in advance, I truly hope you can help because I'm at my wits end and of course am not being paid.

Thanks again.

Terry.

[DiAmOnD T]

Terry,

One of the best laid out questions I have seen on here (normally its just - bus not go, how fix??)

Sounds like you are on the right track in your theory, It takes two sides - Air to the valve block then electric signal to open the right port to supply air to the bands in the box. You may be able to try an external air supply directly to one of the ports on the box and bypass the electrical side.

Another angle to check if you say it feels like it wants to move but won't, is to make sure that the rear brakes release when the handbrake is moved, if it has been sitting for years the brake shoes could have seized up onto the drums

keep us informed on your progress