Hello list,

Brian Carlton made a statement here as follows............. On all SD's from '81-'85, the two vacuum switches on the top of the valve cover serve to operate the EGR exclusively.

They have no direct operation or effect on the transmission shifting.

I've recommended to everyone who has these engines to remove all the Tecalan lines that lead to and from the black box.

One line is the supply vacuum.........one line is the vent.........and the third line leads to the thermo vacuum valve in the thermostat housing and then onto the EGR valve.

These switches frequently leak and have an undesirable effect on transmission shifting however, they have no direct function reagarding control of transmission vacuum.

Well when I short out my black box, two Tecalan leads, in and out, shorted with a tube!
The 1st gear on down shift, gives a big clunk
I already have the EGR plugged!

I have just got my tranmsssion working quite well now, changes up through all the gears nicely

Any thoughts on this appreciated.

Brian