1966 F100, 352 V/8, Auto Trans, Manual Steering Manual Brakes, Drum ft and rear, 2WD Short wheel base. My Grandfather bought this new. I inherited when he passed however my retired Dad kept it for me. I learned to drive this truck counting cows and during wheat harvest. This is the first truck I drove on a dirt road, later graduated to pavement. It has always had a left pull when braking. My daughter and son first driving lesson was in this truck. Now my grand kids are coming from Boston to Okla. City for the month of July and I started planning to take them for a ride in the 4th of July parade and let the oldest stand in my lap and steer the old truck. This introduction is to provide you with the reason this truck has priceless history for me and I will do anything needed to repair this problem. To make this more interesting, I have worked on automobiles professionally since 1977 and I am celebrating my 25th year with my own specialty import auto repair shop. There you go, I should be able to fix this auto but it has whipped me. Wore me out. I can afford to put front and rear disc brakes on this but I want to know why this auto pulls to left when brakes applied. That is why most techs work on cars; they want to know what makes things work. If you can get paid for it; that is better. Complaint; Moderate brake causes left drift, 45 mph or more with hard brake causes lane-changing pull and if brakes are not released auto will get side ways and roll over. BAD. I have read several expert replies here on this forum for the last 2 weeks. After I read something I was unaware of I would check it out, nothing produces a change in the problem. Here is overview, First let me eliminate suspension, using 4 foot pry bar, I-beam bushings, radius arm bushings, king pins, rear leaf springs and leaf spring bushings good. Tie rods and center link good. Front and rear brake shoes new. Front and rear Wheel Cylinders new. Drums within specs according to local domestic shop, Drums have been turned. Replaced front and rear brake flexes hoses. Have replaced metal lines to both rear wheel cylinders. <O</OSwapped drums left to right on rear to try to move problem. Cleaned all moving parts on right rear to try and make right rear work better. No air in brake lines. Still pulls left. Took one of my techs Friday to a strip of new asphalt and watched truck as he drove toward me and braked. No movement on front end or rear suspension. Just Left rear wheel locking up. Saturday morning I took right rear apart, and looked to try and see what I'm not seeing. Installed new spring set. Adjusted brakes until I could not turn drum, backed off 5 clicks. Note, left rear brake always loose. Yet after idling over to test track, first push on brakes at 40mph left rear squealed tire. Raised up on lift, backed off both rear shoes, clamped off flex hose to eliminate rear brakes causing pull. Truck stops straight with rear brakes out of loop. Monday I am going to put new springs on left rear and older springs on right again trying to cause something to affect problem. Overview, Flex hose from chassis to axle new with new metal lines going to new wheel cylinders. How can the left be so dominate? Thanks for reading this unplanned novel, any suggestions or questions welcome. Michael

 

Michael, let me be the first to WELCOME you to FTE! I agree with you that the problem is in the rear. Here are my suggestions: 1. Make sure the left and right are matched, new springs, etc. If the problem still occurs: 2. Swap the drums left for right, and adjust. If the drum is (part of) the problem, the symptoms will swap. If it continues: 3. Put the drums back in their original locations, and swap just the brake shoes left for right, and try it again. If it continues: 4. Swap all the hardware left for right. If the problem continues, I would look at: 5. A bad wheel bearing in the axle, allowing the drum to shift out of round and lock up 6. A plugged steel brake line. Good luck!

 

Wow, only thing I don't think you have done is tried new pads. Unless I missed that in your long list. New springs should be on both sides. All they do is bring the pads back once your done, which it sounds like they are doing since it stops squeling once released. Drums turned, new rubber lines, new springs, new brake cylinders, only thing left is pads. Also if one side is braking harder you could just back off that one side (you stated you backed both off before) until they both lock up together. If you have a test track that shouldn't take too long. Not real great on the ole tires though, lol. Hopefully it wouldn't take long.

As a last resort I would swap out whichever brake cylinder thats giving you trouble.

PS: When I was young and dumb I had a 70 model f-100. Kids would follow too close and I would lock up both rear brakes and scare the heck out of them. Ah those were good times, lol.

 

Thanks for the Welcome. I will do the spring thing tomorrow, I have done the drum swap but not with matching springs. Seems we are on the same page in trying to identify one something as problem and go from there.

 

I did not mention tires are good, 9/32nds tread, 35psi in all 4. More air helps turn the manual steering. I'm not far from doing new brand of shoes and won't hesitate to replace wheel cylinder. Seems right wheel cylinder is not moving shoes as easy as left. Can't figure out if shoes are draging or wheel cyl...weak? No fluid under new cups. With new flex hose, new metal lines and wheel cylinders to both left and right it seems it has to be back plate, springs, shoes or drum.

 

Think those rear brake cylinders are $10-12 each. So if they are cranking them out that cheap they may not be doing a lot of quality control. While your tearing into it pull the right brake cylinder apart. Pull the guts out and run your finger inside. Feel for any imperfections that could impead the piston from moving. Do the same to the piston, feel around the edges. Some fine emory cloth insde will clean up minor stuff. No telling how long it may have sat on the shelf or in a storage facility in china, lol. On your springs issue. If one side is new, then both should be in my opinion. I could see replacing one bad king pin, but we are talking springs here. Much easier to just replace and be done with them. Heck you've replaced everything else, don't skimp on a spring set, lol.

You should have someone snap a couple pics with your grandkids in the parade and post them for us. We always love to see truck pics!

 

You are correct, I sell shocks in sets, pair at the very least, etc. My spring thing was just trying to make the right side work better than it is, I can always put the left on. I'm in a diagnostic phase. However, newer springs are going to be tighter, so I am going to put old on right and new on left. JUST A TEST. Yes, curiosity kills the cat. Don’t worry, I will finish with new on both. Good point you made about how long the wheel cylinders have been sitting on the shelf. I will look there after my spring test. When using a pressure bleeder there is every bit as much fluid coming out of right as is left. Again seems problem has to be in right wheel. I fear I am overlooking something simple and all thoughts are welcome.

 

You'll get this one licked in plenty of time for the parade. Don't forget, if one piston does not have full travel, it would mean one brake pad is pushing against the drum and the other is not. If you welded one piston in place I imagine your pressure test would still show plenty of pressure even though the cylinder was fubar. Just a thought.

 

Welcome Michael, Check the backing plate shoe contact points and make sure they are not any groves worn in them, mine had lot's of ware.

Good luck!

 

Thanks Bill, the back plate did have groves on the bottom 2 contact points. Or the bottom point for each shoe. I used a brilo pad on a...die grinder, to polish all 6 contact points as slick as I could. I applied a lite coat of grease to satisfy myself of minimal resistance. However the grooves on the bottom 2 contact points don’t seem to be repairable. How serious is this? Is back plate replacement required?

 

Not sure? on my truck the rears were hanging up because of the groves, but all the contact points were worn not just the bottom

 

No brake pads on these trucks, just plain old brake shoes front & rear.

The reference to pads is for disc brakes.

 

I set up a jeep Cherokee for my wife to deliver mail in.
I did a complete brake job on it, pads, rotors, brake hoses, on front, and new drums, wheel cyls, hardware kits, and shoes on the back
.
She had a problem with the right rear tire locking up at low speeds about half way through her route.

I pulled my hair out for months trying to figure out what was wrong I'd pull the drums off every thing looked fine...Other than the drum that was locking up was glazed more than the other..
.
If took scotchbrite and scuffed up the shoes and drums she woud get one day out of it before it would act up again..

I had bought the Drums from Schucks they are the only ones that had em in stock.. one was made in Canada and looked fine, and one was made in China and looked like cheep crap.

after months of beating my head against the wall...I figured it must be that chinease drum, because if I deglazed it it would work for a day...

I had them order me in another drum 2 times until I got another made in Canada..That solved the problem

The metal was so soft on the chinese drum it would glaze over and get grippy.....Absolute Junk and a total waste of time and energy..

I knew better than to buy there garbage but I was in a pinch and needed them NOW...

Cost me months of headache.

Greg

 

Lots of good ideas already been mentioned, but a couple of simple things came to mind (you've probably already done these -- but it doesn't hurt to mention). 1) did the shoes on one side get contaminated with oil or rear-end grease? (2) if the brake shoes are asymmetrical (one long, one short) are they installed such that on each wheel the same size shoe is pointing to the front of the vehicle? (i.e., on one side the long shoe is on the left; on the other the long shoe is on the right).

 

Bill, I expect the fix to be simple. I have been guilty of looking for the hard stuff before and when I run out of hard things to attack then I hit myself in the forhead and say, Wow I could of had a V/8. In other words I should have looked there a long time ago. With that said please keep it coming. Brake shoes, long and short. All 4 of my rear shoes are the same length. 10 3/8" long. Measured on outer surface. I have dodged this only because in theory, if both sides are the same I should not have a left bias. Feed back welcome. For those following I did the spring thing today and drove home. I need to drive it some more before I allow results. I should say that I am appealing to the pros on this forum. I hope I am not giving any bad ideas to the novice readers. There is nothing wrong with novice, I'm sure our novice readers are pros at things I should not try.