1988 Ford F350 with 7.5/460 - C6 transmission

I've posted a couple of threads regarding electrical issues and transmission vacuum modulator problem. (links below at the end)

So, we thought we had the transmission issue resolved after replacingg the vacuum modulator and, incidentally, we may have finally licked the electrical problem (still testing).

One of the issues for the transmission problem was that the vacuum modulator was bad but another issue appeared to be a vacuum hose was disconnected.

I found that nothing was connected to the three vacuum ports and I had 3 black vacuum hoses loose in the engine compartment.

Unsure about what they were for I connected them. This seemed to fix the issue with the transmission but after about a week we started having problems with the truck stalling repeatedly. It was starting okay, run for about 1 minute or so and then just stall. This issue started about a week after replacing the fuel filter. I don't know that the fuel filter replacement is an issue but thought i'd mention it.

About a week after the fuel filter work, my son's truck broke down (it would start and run about 30 seconds, eventually the battery would wear down from cranking too much -- finally replaced the starter and now it starts instantly instead of requiring a lot of cranking). At any rate, had to have the truck towed home. Of course, once i got it home it started up and ran okay in the driveway but it did belch out some black smoke and some 'ashy' carbon like stuff. Just that one time and no oil or anything is coming out.

My son decided to try to drive it home to his apartment but it died about 1 mile down the road.

Last night, while working on it in a parking lot, I disconnected the 3 vacuum hoses 1 by 1 and tried starting and driving around the lot. When I pulled one of the hoses off with the engine running (a little ragged / rough) it suddenly smoothed out.

If I put my thumb over the end of the hose the truck would bog down a bit.

Now the engine runs smooth again but the transmission problem is back -- it doesn't shift properly.

If i connect this one hose to the vacuum port and leave something else off, there is a very loud sucking noise coming from the port that doesn't have anything connected. Connecting everything results in the engine running ragged and stalling when trying to drive it.

Clearly this is all way above my head.

Previous threads:

https://www.ford-trucks.com/forums/1...ion-issue.html


https://www.ford-trucks.com/forums/1...l#post16552869

 

Yeah, without pictures or a better description of what you're talking about we really can't help you.

"I connected 3 vacuum lines" isn't descriptive at all. There are a lot of vacuum lines in these trucks - which three did you connect?

 

my sincere apologies and i don't mean this sarcastically but if I knew what i connected i probably wouldn't be relying on you guys to help me ... i wish I could tell you what they are and what they do, i've been watching videos and looking at photos of the engine to see if i could find anything that would help me identify what these 3 lines do.

All of them are large black rubbery type vacuum lines which differ significantly from most of the lines i see in the truck. I can definitely take some photos but two of them are in tough spots to photograph.

thanks for taking the time to respond just the same.