86' M1008 - Contemplating Chevy 350 engine swap

[Commander5993]

Yes, This pump provides vacume for the transmission modulator. Since the 6.2 has no throttle valve like a gas engine there is almost no vacume in the intake manifold. This pump provides the vacume and is piped into the valve on the IP then down to the vacume modulator on the passenger side of the transmission. Just above the trans oil pan. It's a round canaster about 1 1/14 inch in dia. You rotate the valve on the IP eather forward tward the rad, or backward tward the cab. This will adjust your shift points to your preference. I adjust mine to shift around 2300 PRM's to keep the engine in it's max tourque range. Any higher than that and my truck does not pull heavy loads as well. Too high and it over revs and looses power. Too low and it boggs down and struggles to accelerate. Adjust yours to your loads and driving style.

hum, ok. I'll adjust mine after I get it back up to running shape.
I wonder how it worked before without the vacuum even being connected? It seemed to shift ok and such...

 

[ken]

that is strange. The engine should have reved really high before shifting with out the vacume pump hooked up.

 

[Recovry4x4]

Is your truck completely stock? Is there any chance someone could have retrofit a 700R4? They do not require vacuum to operate.

 

[Commander5993]

Is your truck completely stock? Is there any chance someone could have retrofit a 700R4? They do not require vacuum to operate.

As far as I know it is stock, it only shifts up to 3rd gear. I know it doesn't like to go over 55mph. It will go a bit more, but it drives best at 55mph.
The engine and transmission have been apart, but if it was by some one or the military depot, I do not know.

 

[Commander5993]

Is your truck completely stock? Is there any chance someone could have retrofit a 700R4? They do not require vacuum to operate.

Is there a number or some sure way to ID the transmission?

 

[The FLU farm]

Is there a number or some sure way to ID the transmission?

Quickest and easiest is probably to Google "Automatic transmission ID", or something similar. With the outlines of the pan gasket you can identify them.

 

[Commander5993]

Quickest and easiest is probably to Google "Automatic transmission ID", or something similar. With the outlines of the pan gasket you can identify them.

Thanks for the info FLU farm

From what I was able to find, the TH400 has a pan with 13 bolts and it looks like this:



And the transmission pan on our truck looks exactly like this gasket, and also has 13 bolts.

So... why would someone just disconnect the vacuum line?? Could the valve on the IP or the module on the transmission be bad, so they just decided to disconnect it?

From the info Ken gave earlier, I think I found the valve on the IP where it should connect. If I am correct, there are two ports on this valve, one to connect to the vacuum pump, and the other that should connect the the hard line going to the transmission?
Neither port is connected to anything... its just sitting there.

Once I get the intake and etc reinstalled on the engine, I'm going to get some new vacuum hose and reconnect this.
The thing is, it seemed to have shifted fine, didn't rev to high, didn't have hard shifts either. Guess that's why I never looked into the details on how to adjust it.

 

[The FLU farm]

Once I get the intake and etc reinstalled on the engine, I'm going to get some new vacuum hose and reconnect this.
The thing is, it seemed to have shifted fine, didn't rev to high, didn't have hard shifts either. Guess that's why I never looked into the details on how to adjust it.

I'm curious about how it'll shift with everything hooked up. And envious of your already functional shifting.
In my case the shifts are very late, due to a different model pump that wouldn't accept the original setup. I've lived with it as is for a long time, but it would be nice to get it to shift earlier. I've thought about hooking the vacuum pump directly to the modulator - if it shifts too early I can always downshift manually.

 

[ken]

If the metal line going down the transmission is still there try to reuse it. I tried rubber vac hose with out good results. I believe the metal line inside dia meters the vacume.

 

[Commander5993]

I finally took my thermostat housing apart today, found an ac delco 14077122, which is a highflow... but either 190 or 195 degrees... depending on which website you look it up on.
I found and ordered the Robert Shaw 370-180 that you suggested, seems a lot of people use it in older vehicles. I think it will be a better replacement than the mr gasket, just going by the many reviews. I know you said you haven't had any trouble with them, but it seems only a few people have gotten a mr gasket #4367, that worked for more than a few days.
Anyway, Thanks again for the info Ken

got the robert shaw thermostat in today... but it was the wrong part number. its a 301-180 instead of the 370-180, so I have to send it back.
But from what I have seen online the 370-180 is no longer being made. So I'm going to use the AC -Delco 12TP5D for the time being. If I can find another brand like the Robert Shaw 370-180, then I might order one.

 

[ken]

Try flowkooler.com. They still carry them along with high volume water pumps