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Vacuum Modulator replacement


Dragstart

Forum Member

U.S. Military - Veteran
Joined
Sep 2, 2025
Messages
15
Points
101
City
New Smyrna Beach
State - Country
FL - USA
Vehicle Year
1991
Vehicle
Ford Ranger
Drive
2WD
Engine
3.0 V6
Transmission
Automatic
Is there a prefered method for getting the cat off?

Rusted/frozen bolts at the cat to manifold won't budge!

Two bolts are easy to get at to cut or grind out. The third one seems almost totally inaccessible.

Any tricks for either getting cat off or for somehow sneaking the new modulator valve in?

TIA
 
What do the bolts look like at the exhaust manifold connections?

Could take it to a exhaust shop and let them torch the cat bolts off, and install new bolts. Unless you have access to a torch yourself.
 
Thanks for the reply, and I had already considered that going to a muffler shop would be the only way to get those bolts out. But..........that outside upper is totally inaccessible by any method. Torch, grinder, chisel.
Every auto manufacturer's engineers seem to take great pleasure in making repairs difficult or seemingly impossible, but ford engineers are a little better than most at it.
Every avenue I tried by taking off parts for access were blocked, leaving only pretty extreme measures, especially considering that the vacuum modulator is a VERY simple replace if you have access.
I finally did my best contortionist and reached into a small channel of opportunity and got the ten MM bolt out that holds the clamp that holds the Vacuum Modulator in it's hole. All done blind only by feel. I weigh 142 and have hands and forearms that allowed this access. If you're much bigger, you're out of luck doing it this way.
I had lost my mirror, and as my wife was going out, I had her pick me up a small mirror to try and see what I was doing, but got done before she returned. Going out now to see if everything looks ok, and not even sure if I will be able to see up in there with the mirror.
 
And I live in Florida, where on January 3rd, it is 75 degrees. Also could not have done this with no gloves and cold hands.
 
I had to pull my transmission so I could change the front seal that the torque converter slides past going into the transmission.

To get the bolt and nut your talking about out I had to disconnect the Y-pipe from both exhaust manifolds and then disconnect the cats from the extension pipe that goes to the muffler.
At that point I was able to lower the cats far enough to get a sawzall blade in there and cut that bolt you're talking about.
I had to get the cats and the Y-pipe out of the way to get the transmission out.

I will warn you ahead of time that all of my exhaust manifold to Y-pipe bolts / studs broke on me. I had to then drill them out and to do so I had to take my manifolds off the heads.

When taking the manifolds off I broke three of the manifold to head bolts on the driver's side. All top bolts.

Needless to say it was not a good day or even week for me because I was working outside as well I had to deal with weather rain and so on so forth.
I could only work on my truck for an hour or so a day one day I got 3 hours and that's when I made the most progress.

I to have to change my vacuum modulator I believe.
Because my transmission is now slipping and I'm going to try the vacuum modulator before trying to find someone to rebuild my transmission.

I'm 5'5 and weigh almost 250 lb so my hands won't get in there like yours did.
I'm glad to hear that you was able to change your modulator without getting the cats out The Way.

I wish you more luck in the future and hope you're able to have fun with your truck.
 
I feel your pain. And I feel a little lucky. Still have to get the VM adjusted, slipping on the 2-3 shift, never did before. I'm also going to do the bands, haven't even looked at that side of the tranny yet. Afraid to, to tell you the truth.
 

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