76 d700

70chall440

Active member
Well I thought I had an idea (derived from another forum); it was suggested the one or both of the ports on my new MC has a residual pressure valve, so I pulled the lines again but no joy, there isn't anything in the ports so I am back to where I started. I believe I am going to have to pull the wheels and brake drums but it seems that those lug nuts have not been off for some time and are left handed. So I am soaking them in penetrating oil and then will look at trying to break them loose.
 

70chall440

Active member
I wonder if there are any brake guys on here, I think I need to find someone who understands medium and large truck brakes.
 

RonG

Well-known member
You are being pretty thorough,if you have a wheel cylinder hanging for whatever reason it would only take one hanging to give you problems.I know that that is pretty obvious but sometimes we look for too much trouble.Ron G
 

70chall440

Active member
IMG_2493.JPGIMG_2494.JPGSo, I did some automotive archeology tonight on the truck. I pulled the massive front tire off, then got the hub and drum off. I couldn't find anything outwardly wrong although it was pretty dirty and the axle bearings are due for re-lub. I could not spin the hub by hand, this could be a result of the massive amount of surface contact area, could be also be in part to the bearings being a little dry. I did try pushing on the brakes and nothing happened; I didn't lean on them hard because I didn't want the wheel cylinders to pop out but I just wanted to see if anything would happen, it didn't. The brakes were tight on the hubs but not excessively so. Doesn't look like the cylinders were/are leaking but to be honest, I am not sure if they are working all; however when I have tried to move the truck it seems that they are.
 

70chall440

Active member
An interesting side note is that the manual I have which goes to 75 shows these same brakes except pointing front/back whereas these are up and down (top and bottom if you prefer). Looking at them closely, I would say the back plate has been off at least on the drivers side (haven't checked the pass side yet). So either they made a change in 76, omitted this setup in the manual, or someone put them together wrong. I am going with option #1 at this stage as both sides are the same, so if someone did change it up, they did both sides. My manual does should a top/bottom set up for a rear axle, but not a front.
 

RonG

Well-known member
It does not look like there is too much lining on that top shoe,could the wheel cylinder be hanging by over extending?I realize that is brake work 101 but that is all I can see from here.I have an FSM for a '75 and my next one was an '83.I get FSMs for all of my Mopars.Ron G
 

Oxbow

Well-known member
Just a side note, if you have had a seal leaking it can make the brake lining REAL grabby. Had that happen on a 95 Ford that I used to have; would lock up one of the rear tires instantly (drum brakes).
 

70chall440

Active member
I am not sure how much brake lining there is supposed to be actually; the FSM I have says replace the shoes if there is less than 1/16 to the top of the rivet; I think I am slightly over that. Now, I know what anyone reading this is thinking; why not just replace the shoes. Well the short answer is that I cannot seem to find them. I am still looking.

Reference the leaking aspect, I agree however it doesn't look like anything was leaking but I haven't looked at the other side yet. I ordered new wheel cylinders, seals and a hydrovac booster. still looking for shoes. Not sure where/who could cut the drums but I am not sure if I will do that. While there is the "right" thing to do; the truth is that this truck is not going to be used all that much and I really do not want to dump a ton of money into the brakes; yes I want them to work and be safe but I don't think I need to rebuild the entire system.
 

70chall440

Active member
2AD96-321PG-1.jpgUPDATE - found the shoes (helps if you look in the right spot). the picture of them doesn't look like they have a whole lot more meat on them then the ones I have.
 

70chall440

Active member
those things in the middle of the picture are the wear indicators and I just noticed that the ones in the picture have a stepped top, I do not believe mine do which leads me to believe that mine have worn down and perhaps they are worn out, over extending, etc.
 

70chall440

Active member
just checked the FSM, the shoe material is .312 when new, I will remeasure mine but I think they are around .250.
 

70chall440

Active member
Today's update: I picked up the new wheel cylinders and commenced to disassembling the left side brakes. Not overly difficult just a little different than what I have seen in the past. Once I got the brakes off, I took off the brake lines and then the wheel cylinders. I discovered that both wheel cylinders on the drivers side were completely jammed with gunk which appears to be a combination of rust, water, dirt and brake fluid. I tried to disassemble them but they are stuck together. What I think is that that the brake line pressure did force them out but then they were stuck there which is why I was having the problems. I cannot say this is "the" problem but is certainly is a "a" problem. Have to wait until next week to get the new wheel seals so I can repack and reassemble the drums and hubs. Tomorrow I will do the right side as I have to build one of the brake lines; it wouldn't come off so I had to cut it.
 

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70chall440

Active member
I played with the old wheel cylinders today; I discovered that they would move a little, then stick. If I played with them (pushing in and out) I could get a little more movement but not a lot. I tried blowing them apart with compressed air, they wouldn't come apart. I am very confident this was a huge part of my problem. I ordered a new booster, but I think I am going to reassemble everything, bleed it again and try it without removing or replacing the booster.
 

RonG

Well-known member
I have a wheel cylinder hone but for the price of replacement wheel cylinders these days I have not used it for years.Guess you got it under control.Ron G
 

70chall440

Active member
Yea I have one too, but I could not find a rebuild kit and for $42 a cylinder and given the old ones condition, new was the way to go. I think this will go a long way to fixing it, however until it works I wont be happy.
 

70chall440

Active member
Today's update: got the bearings packed, wheel seals installed (4" wide and cost $53 each..). Went to install the drums, but the outer wheel bearings wouldn't fit, so I had to remove the drums, clean off the spindles and figure out what was going on there. The drivers side had a small burr on it but the pass side seemed fine. I polished them up and removed the burr and got the bearings to fit. I then reassembled the whole deal and went about bleeding the system. Got that done and put the very heavy and large front wheels on. At that point I had to test it out; well at first it seemed good but then it went back to essentially what it was doing before, although a little different. When reversing when I hit the brake you can feel the front (I think it is the left front) grab and hold, when I put it into drive it releases and moves until I hit the brakes and then it is the same deal. It seems like brakes are releasing but slowly (but a lot faster than before). In my mind it seems like if I played with it, it might sort itself out, but then again I still suspect the check valve in the booster is hanging up. Since I ordered a new booster, I guess I will swap out the old one or perhaps I will just remove the old one and take apart and see how much gunk is in it, clean it out and reassemble it. Problem there is that there isn't any rebuild kits for it so if I tear it apart I will most likely have to install the new one anyway.
 

70chall440

Active member
I am trying to figure out what the lug nut torque should be on this truck. The FSM (which covers up to 1975) shows a 3/4" stud torque being 200 ft lbs, however everything else I can find of a 3/4" stud says 450-500 ft lbs. I know they were exceptionally tight when I removed the fronts but that might be due to some overzealous truck stop guy.
 

RonG

Well-known member
I don't think I ever saw anyone torque those lug nuts and I have changed a lot of 24" rubber in my(rainy) days and I never did.My employer provided an impact gun with a spline on the end of it to put the socket on and the air hose to it was at least 1" diameter and we used to really hammer those lug nuts so who knows what was used to tighten them down?It seems like a 3/4" impact wrench would be enough.Ron G
 
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