In a pickle

[Flathead]

I have a 1984 Chevrolet 6.2 Diesel in a Chev 30 Motor Home. It had trouble shifting up. Checked and had no vacume at diaphram. Checked back to pump and have over 20" vacume. It would appear there is a problem in the regulator. For days now I have been trying to remove it but since this is a snub nose cab I cant get into the dog house far enough to see how it is put together,to add insult to injury I cant remember which vacume line goes where and which wire goes to which terminal. Can anyone give some advise to this old man? Be nice now.

[WeaselWerks]

what kind of transmission do you have in your rig? Usually the vacuum on the diesel is generated from a pump, and isn't proportional to the throttle position the way it is on a gasser... I guess this is where your regulator comes in... I can't say I've come across something that complicated (throttle vacuum regulator) on vintage 1984 technology, but hey, never too old to learn something new today. ;)

I think a few more details, and someone will jump in with a more definitive answer.

[ccatlett1984]

no vacuum at the regulator would cause poor shifting, since you have good vacuum at the pump, its a cracks line somewhere, you should replace all the vacuum lines that look dried out, or are cracked and hard to the touch. I'm not sure of the routing for the lines in your application. But you dont need to pull the regulator yet, get vacuum to it first, then see if it fixes your issue.

[Robyn]

You have a turbo 400 tranny
The issue is most likely the vacuum switch that is mounted on the RH side of the injector pump.

These little creatures fail in due time.
Be sure you have good vacuum going to the switch. Be sure your line from the switch to the tranny is in good order too.

Replacing the switch is a simple 2 bolt thing. Be sure to install the new switch in the same relation as the old one.
The switch is indexed to the throttle shaft and rotates the switch to provide a more or less linear control over the vacuum.
This vacuum controls the modulator on the 400 and this controls the up and down shift points.

With the throttle closed and the engine running you should see 20+" hg at the Mod as the throttle is depressed the vacuum will drop off markedly.
The whole process was designed to mimic the vacuum that a gas engine would produce under load conditions.
The system works fairly well when adjusted properly.
If you need the part number for the switch let me know and I will dig around. I have one on the shelf for a project rig.

As far as the hose routing they will only work one way. If one way does not work, swap the hoses.

If you replace the switch with a new one just use the marks left in the plastic switch by its attaching bolts as a guide as to where to place the new one as this will get you close.

Once your up and running if the tranny shifts too hard it means you have too little vacuum and need to adjust the switch slightly Clockwise (Looking from the RH side of the IP
If the shifts are too soft you would do the opposite.

Be sure you dont get the shifts to sloppy as this can and will ruin the clutches in the tranny.

A little firm is better. Usually installing a new switch in the same spot will be quite fine.

Good luck and keep us posted

Robyn

[Flathead]

Thanks everyone for your good advise. This is a great web site. Robin,please give me the part # for the switch,also where is the best place to buy one.

One more thing,please,since I cant see the switch or regulator can anyone give me an idea where the bolts are and what size wrench I need.

Maney thanks
Flathead

[Robyn]

The switch is on the RH side of the injector pump.
I believe they take a 10mm socket to get loose depending on who may have worked on it.

I will look asap for the part and the number for you.
Later today I can do this.
The part is a GM item only so a Chevy or GMC store is the ticket

Robyn