Well this is a bit of a long story but if someone can help I want to give as much complete info as possible.

My 86 F150 5.8 4V HO was running terrible.

At the suggestion of a forum member I did the spray test and found a ton of vacuum leaks. So I started replacing vacuum lines. I got done with basically the drivers side of the engine area and all seemed well. Jumped in the next morning and the tranny wouldn't shift!

Saturday morning I looked at it and there was a line coming down from a three way fitting on the firewall that connected to the vacuum modulator on the transmission (a C6). I hooked that up and ran around the block and all seemed well.

So I replaced the vacuum modulator and I'm still stuck!

After hooking everything back up I still don't have D (drive) on the transmission. I can manually shift from low to 2nd but if I put it in D all I get is low.

I found a big vacuum connection that isn't hooked up and for the life of me I can't figure out where it goes.

Looking at the front of the engine it is approximately at 4:30. It comes off the manifold as a major vacuum supply that runs to the brake booster and it's a short nipple with four small fittings running off it. I've replaced the two on the left side okay but I noticed on the right side one is plugged and the other has had a hose pulled off it. The connections on the right side are slightly larger than the ones on the left. I tried just adding a short length of hose and plugging it to no avail.

Could this be the line that runs to my vacuum modulator on the transmission? I thought that one ran off the three way fitting on the firewall.

I'm going to post this in the transmission area as well. This is driving me nuts! I'm going to have to go to the junkyard to see if I can find something hooked up to see what it looks like.

I will try to add some pics when I get home from work tonight.

 

Have you seen this?


1985 351w vacuum diagram - Ford Bronco Forum

 

Actually I did find it in one of the thousands and thousands of searches trying to fix my problem

And I am happy to report that my problem is fixed, sort of.

In all the responses I've received for help and in the searches I've done somewhere I read a poster (on FTE I believe) who stated something to the effect that "I would want as good a vacuum to the modulator as possible."

With that in mind I ran directly off the front manifold vacuum port (the one that I found an empty port on) and plugged that into the transmission manifold connection and VIOLA! I drove to work this morning!

I'm going to start a new thread to chase down my remaining issues.

Filthy (wish I knew your name) you've been the lead in great help.

My confidence has gone up two notches with this small success. The truck runs like new, literally. Two pumps and zing! Maybelle high-idled perfectly, no hesitation while still a little cold, idles like a purring kitten and she runs like a beast!

Again, thanks to everyone.

 

WuHoo! Success!! Glad you resolved your vacuum to trans issue and happy to hear you won't be hesitant about turning a wrench or two on your vehicle(s). And thanks for the kind words.

.....and my given (haha) name is Mike. Look forward to try and help you (if needed) in the future.