I looked through many posts, but was not able to find what I needed in the detail I need.

This is for a 1991 350SD. I am trying to get the transmission vacuum control adjusted properly.

I have seen some posts for the older 300SDL cars (maybe it would be the same?) that suggested that the initial adjustment needs to be made at the transmission modulator before setting the Vacuum Control Valve. I guess if I do that I need to jury rig a banjo bolt to check the pressure?

On the 1991, the adjustment to the VCV is made by rotating the VCV. The thing I was wondering about is that most adjustments seem to say to check the vacuum on the line going to the transmission, but that is after the blue vacuum valve that is between the VCV and the transmission.

I could have sworn that the VCV is to be adjusted prior to the blue vacuum valve. I think there is supposed to be some sort of drop in vacuum as the throttle is depressed and you have to check the output of the VCV. The output of the VCV is a three pronged connector with the vacuum pump on one connection, the interior climate control system on one connector and the output to the blue transmission valve as the third. At least that is what I can tell.

So I assume you have to plug the connector going to the climate control to get a good reading. The other thing I was trying to think through was trying to give it full throttle. I read somewhere that you needed to disconnect the throttle linkage, but isn't the part that drives the VCV also the part of the linkage that is on the Injection pump and so would also inject more fuel? In other words, if I move the disconnected linkage on the pump, won't it rev the engine anyway?

Also, I think there are some measurements for the vacuum I need to adjust to I think?

Probably making this more complex than it is, but I want to understand it in my head before I start messing with it.

The symptom is that the transmission is doing like what feels like a double shift. It shifts up (2-3 I think) and then seems to shift right back down. Not sure if it is down or up, but it's like one shift and then another back to back. Not sure what it could be so I'm trying to be sure the pressures are right.

The transmission shop had way overfilled it and I already fixed that.