Is dieselgiant wrong?
 

I've recently bought a very stock, very nice '84 300D. I'm interested- in what seems like a consensus- with the elimination of the two lines that feed vacuum to the black, two-lever switch box located on top of the valve cover.
Now, there seems to be conflicting info here- I read here that this device has nothing to do with the proper operation (shift points, smoothness) of the AT, being only part of the lame US EGR system.
However, reading DieselGiant' s instructions, I'm told that this valve/ lever device has everything to do with the AT's operation... Am I missing something?

Thanks for your advice
Will

Yes they do.But I got rid of them,and run line to 3 way conector,one end plugs on the vac modulator on injection pump,the other the vac line from transmission goes in.Egr is the worse thing for diesels.

I have removed or completely bypassed the egr system on every MB diesel I've owned. DG may run into legal issues were they/him to mention otherwise.
In the pic you may be able to see my switchover valve is bypassed also.

I certainly like the cleaned-up appearance you have there.

Do you have an official MB part number for the white- colored plug next to the firewall?



(Kidding)


thanks for your help

That is a seemingly common misconception. The purpose of the valves is to operate the EGR valves. However, if the valves leak, the operation of the transmission can be affected. So, folks replace the valves, then the transmission shifts better. So they conclude that the valves operate the transmission. (This applies to the subject vehicle; other models are different.)

I thought it also had something to do with softening the shift while cold but that is really just speculation.

Is that the electrical switch that is usually mounted on top of the camshaft cover?
What its purpose?

DG means that if the valves are leaking they can have a big impact on transmission performance. Working normal or removed, they have no impact on the transmission.

What he said. Mine leaked, and after removal, shifts got better.

Exactly.

For W123's, only on the 84 CA and the 85 Federal / CA are there any provisions for shifting performance adjusting with temperature. they are designed to shift softer when cold.

dd

I have run without the valve for years with no issues with my trannys.

The 240D is the only one that the valve on the valvecover affects the transmission.

I think you're confusing the black box on the cam cover as being electrical, it is not, just vac lines going to it.
The switchover valve is located on the first firewall, the pic shows a new hard line from the manifold to the switch over valve, I have just bypassed it on this car yesterday, and am going to take it for a drive to see if there is any difference. The one on my CD has always been bypassed.

your 85 has an electrical switch here, because the EGR is controlled electronically.

see my answer above... he has an 85... it's different from all the other years.