I pulled the old 86 out of the weeds

Old Goat

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I went through the same thing on my 86.
Checked vacuum with a gauge, and checked out fine.
Push peddle and vac would drop, release and hit again and
really dropped.
Took Pump a while to build back up.

Driving the truck and one application and she would slow down, 2nd time and like no vac.
or like pushing on a brick.
next time would be kind of ok.

Took it to a shop. they went through everything, Pads, Rotors, Drums, shoes etc....
Pick up truck and said they could not find anything wrong...good Vacuum etc...
leave shop, at corner intersection...no vac assist...

Things narrowed down to the Pump, so replaced it. I did keep it just incase that was not it. I have a shop full of just in case parts...LOL still the same thing.
I did notice a HISSS from under the dash when pushing peddle in slightly, and was told it was normal to do that.

I finally replaced the Brake Booster, and that was the problem. They have never worked this good in the 131K miles and almost 8 yrs of care giving her.

I think this is the 4th one that has been replaced. Finally have one that will just about put my nose on the Windshield.
These so called Rebuilds from O`Rielly`s are a crap shoot,


Goat
 

trythis

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Thanks for the reply turned out to be the vacuum booster. So I've been looking for a good reason to change over to hydroboost. I have the booster and the power steering pump on my 96 F superduty parts truck and I was really surprised to see that they both will interchange on this 86, at least it definitely looks good like it'll fit.
Question I would ask is if I should use the master cylinder that is on the hydroboost or should I stay with my old master cylinder? The 96 F superduty parts truck that I got the hydro boost from is disc brakes all the way around . the 86 is disc in the front drum in the back.
 

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TNBrett

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Thanks for the reply turned out to be the vacuum booster. So I've been looking for a good reason to change over to hydroboost. I have the booster and the power steering pump on my 96 F superduty parts truck and I was really surprised to see that they both will interchange on this 86, at least it definitely looks good like it'll fit.
Question I would ask is if I should use the master cylinder that is on the hydroboost or should I stay with my old master cylinder? The 96 F superduty parts truck that I got the hydro boost from is disc brakes all the way around . the 86 is disc in the front drum in the back.
I used my original 1-1/8” master cylinder with the hydro boost conversion, and I did not modify the pedal arm. I’m very happy with how it works. I elongated the bolt holes in the MC and made a simple bushing to keep it centered in the hydro booster.
I didn’t even open up the brake lines so I didn’t even have to bleed them again. Took about 2 hours to swap over to the HB for me.
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trythis

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I used my original 1-1/8” master cylinder with the hydro boost conversion, and I did not modify the pedal arm. I’m very happy with how it works. I elongated the bolt holes in the MC and made a simple bushing to keep it centered in the hydro booster.
I didn’t even open up the brake lines so I didn’t even have to bleed them again. Took about 2 hours to swap over to the HB for me.
Is that the 92 that you're working on? I see it has the aluminum master cylinder mine is 86 and has the cast iron master cylinder. I would hope to get by with only two hours labor as you did but I already have that much in getting the old parts from donor truck lol. I don't yet see any reason to alter the foot pedal so I'm hoping I don't have to get into that.
 

TNBrett

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Is that the 92 that you're working on? I see it has the aluminum master cylinder mine is 86 and has the cast iron master cylinder. I would hope to get by with only two hours labor as you did but I already have that much in getting the old parts from donor truck lol. I don't yet see any reason to alter the foot pedal so I'm hoping I don't have to get into that.
Yes, it's the 92. I would think you could modify the cast iron master cylinder similarly. If you go with the larger 1-5/16" master cylinder, I would modify the pedal. Its all about keeping the same volume of fluid pushed out for the same amount of pedal travel.

That 2 hours didn't include the time I spent rebuilding the Hydro Boost, or shopping for parts, but the actual conversion for me was pretty straight forward.
 

trythis

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Yes, it's the 92. I would think you could modify the cast iron master cylinder similarly. If you go with the larger 1-5/16" master cylinder, I would modify the pedal. Its all about keeping the same volume of fluid pushed out for the same amount of pedal travel.

That 2 hours didn't include the time I spent rebuilding the Hydro Boost, or shopping for parts, but the actual conversion for me was pretty straight forward.


My master cylinder the cast iron one bolted right up the depths for the rod is the same on both cylinders. Sure hope I don't have to get into that pedal travel adjustment I don't have a clue how that works. Guess I'm just gonna hook it up see how it works.

I'm changing my power steering gearbox at the same time. Got that power steering pump out of the way can access them hoses is a little easier, gotta be done anyhow. Thanks for the help.
 

1mouse3

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This is what I did with my pedal for hydro, just drilled a hold for a 9/16 bolt and think was 3/4 an inch higher. Had someone weld it and drilled a hole for the retaining clip, its worked fine like this.


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trythis

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Well we got all that stuff done and got some new tires on it and it looks like it's good to go. Just wondering what a truck like this might be worth.
Thanks again for all the help!!
 

IDIBRONCO

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Asking prices and what it's actually worth are WAY apart these days. If you want to know what it's "worth"' look at Kelly Blue Book or NADA. What it's worth to you can be much different than either the asking price or the book price.
 

Big Bart

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You have a crew cab which is desirable. The paint looks a little rough. You have new tires so if runs decent and everything is working you should be at least at $6,500. But COVID has many higher than that so hard to say.
 

Nero

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Being as my old man just sold his '88 for $6000, I betcha a CC would go for a lot more.
 

Farmer Rock

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I just sold my 87 stock 6.9 zf5, rclb f250 4x4 for 5k, and it was used to work, had 211k miles.
Prices are plain crazy right now, I never expected it to go for that.

Rock
 

trythis

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Not so good to go. Got 86 out on the highway today and the drive shaft or something in that drivetrain it's not balanced vibration is fierce.
I'm sure I can find a local shop to make me up a drive shaft.
Thing I'm wondering is. If I'm going to do this new drive shaft do I really want to stay with this NP435 transmission I really would like the 5 speed. But I don't have one, I do have a automatic out of line 1996 F 450 parts truck. But I'm not familiar enough with the electronics to make that work, so maybe I could trade it. Any advice or ideas would be appreciated
 

Big Bart

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Get it up on Jack stands and take a look around. Maybe have someone run it up so you can see where the vibration is from. You may have a bad u-joint or center support bearing if your truck has one. Maybe a bad pinion bearing or yoke. Maybe take your drive line in and have them balance it. Dirt and mud can also be an issue. You said you pulled it out of the weeds. Try getting your driveline clean. But if your drive shaft is not dented or bent keep looking.

Also when you got new wheels did you have the balanced?
 
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