Truck veers to the left when braking

[Cowboysculptor]

Hey guys,

I’ve been working on my 1969 f100 with RWD and drum brakes on all four, and I have an ongoing problem: when I put on the brakes, the truck veers left.

The things I’ve done to try to correct this are, rebuild the brake pistons, replace the front brake hoses, replace the front wheel bearings, and replace the extremely worn radius arm bushings. The brakes all seem to be functioning just fine. Replacing the wheel bearings got rid of the play in all directions that the wheels had. Am I right in assuming that the problem is in the front?

Also, the bearings in the steering column have fallen apart. All the pieces have been removed, but obviously there’s a lot of play with the shaft. As I drive straight, I can let go of the wheel and it tracks straight and true. Could the steering column (which I’m about to replace) be the culprit? Where else should I be looking?

Thanks for any help.

[Ranchero50]

Right side brakes not holding or left holding too well. If it's a constant pull, suspect the right side. if it's just a nudge and then OK balance the adjustment. Do a long downhill braking and then see if one feels hotter than the other. If the brakes are all the same temp move to the suspension. You should be able to brake hands off and it should track straight if everything is working correctly. If you can while going down the road but not braking I suspect the brakes, not the suspension.

Ideally you'll pull all four drums and check the backing plates for notches where the shoes have rubbed over the years. Check for oil on the linings etc. Once the shoes are assembled gently hit the brakes to ensure they move but don't blow the pistons out of the cylinders. Assemble and set the drag the same from and back, side to side.

[MadMike]

Does the steering wheel turn to the left when you brake?
If the steering wheel itself turns then most likely the front braking system has an imbalance issue.
When it comes to brakes, with the exception of dragging, you can never have too much on a stock system. I would suspect the right side is getting hung up mechanically and not applying properly. Since the system is front rear split, it automatically balances hydraulically.

Rear brakes will not affect steering angle on flat dry pavement under normal braking. Under heavy braking rear wheel lockup can cause a spin, and on slippery surfaces a rear unbalanced system may cause the truck to yaw(dogwalk) under braking. But not self steer.

If the steering wheel stays straight then most likely it is a suspension/steering linkage issue. Sloppy tierod or cross alignment issue.
Unloaded the steering is fine, loaded(under braking) a component is allowing more play and causing a wheel to self steer. Sloppy tie rod etc.

Steering column should not cause any issue with the steering/tracking. Only it will be harder to control as the steering wheel oscillates around rather than simply rotates. It controls the steering box, now if there is slop in the steering box it may cause some left/right darting under hard braking but not a pull per se.

If you could have another set of eyes watch the wheel(s) as you brake that would be ideal. Video would be better so you can analyze it yourself.

[Ohiotinkerer]

Even with all new everything mine still pulls to the left the first 2 or 3 times I hit the brakes.....dad says everything he's ever driven with 4 wheel drums has done it no matter what he did to them......and he's 73 so he's driven a lot more stuff with them than I have........

[Cowboysculptor]

When it comes to brakes, with the exception of dragging, you can never have too much on a stock system.

I'm not quite sure what you mean by that.

Thanks for the replies you guys, I finally got a little free time without rain to test things out and here's what I've got:

After a little running around, braking down hills, I found that the steering wheel did in fact turn to the left, but that all four brakes felt about the same temperature, that is, a little hot around the edge of the drum, cool otherwise. Up on jacks, the front wheels had about the same drag without brakes, the same grip with brake pedal blocked down. (Read: 2x4 between pedal and steering wheel.) Am I missing something?

One thing I left out which may be important is that I recently added a power brake booster and new master cylinder, but the brake system seems to work fine and the lines are all bled. Any more ideas?

[MadMike]

When it comes to brakes, with the exception of dragging, you can never have too much on a stock system.

I'm not quite sure what you mean by that.

If any 'fix' requires reducing braking power on an otherwise stock system, there is something wrong with the 'fix'.

I found that the steering wheel did in fact turn to the left, but that all four brakes felt about the same temperature

Fronts should feel slightly warmer than the rears. With harder braking there should be a greater heat difference between front and rear.

When the wheel cylinders were rebuilt did you verify that both sides of the wheel cylinder cups/pistons move. I've had 'rebuilt' wheel cylinders that had a slight ridge from rust that prevented a cup/piston from moving but did not leak. This allowed hydraulic balance and actuation of the system, but the mechanical side was unbalanced as one shoe would not move out. Took a while to figure out why the car would not stop quite as well as expected, it was a rear cylinder so no steering issues to help pinpoint a possible problem

Shorter shoe should be facing forward, longer shoe to the back. If both shoes had the same amount of material then one should have been marked for use in the leading or trailing position. Verify the two short shoes are not on one side and two longer shoes on the other. That would also cause a brake imbalance. Verify that all the hardware has been installed correctly and the left/right mirror each other.

With the truck driven on for a bit recheck your wheel bearings as well. They should have taken a 'set' and may require some fine adjustment. No need to kill the bearing, just need to tighten the nut until the slop in the bearing clearances is gone. I usually snug up the nut until there is no more play in the drum/rotor when I rock it at 12 & 6 O'clock positions. Just make sure it's not sloppy king pins that you are trying to adjust out.
Loose wheel bearings will affect how well the initial adjustment and how quickly the shoes grab the drum. If the self adjusters were overly tightened they can hide a loose wheel bearing adjustment. May want to back off the star adjuster a bit to verify the bearings are adjusted correctly and not the shoes holding the drums.

Verify the star self adjusters have the same adjustment from left to right. Are well lubricated and not worn out. After I have set the wheel bearings I usually rotate the adjusters until they stop, never force them that one extra click as that will cause shoe drag. Which can cause one side to pull more under braking.

And finally if the brakes seem to be functioning properly, verify your alignment is correct.
Suspension bushings and king pins cannot be overly worn or sloppy, and the alignment shop should have you sit in the truck as they adjust everything. These trucks are fairly sensitive to roll/bump steer. Setting the alignment without the driver, or at least the same weight as the driver, will not give a correct alignment.

And of course, tire size(including wear), wheel size and offset should be equal from left to right.

[Cowboysculptor]

As always, thanks for the detailed response. I’ve rechecked the bearings: check. I’ve rechecked the brake adjustment, and even tightened the right side ever so slightly more with no change. The shoes are oriented correctly.

So that leaves cylinders, which are cheap enough, so I’ve ordered a pair. I’ll change those out and see what happens.

[Cowboysculptor]

Just one more thing occurred to me. The trouble started just after installing this power brake conversion kit: http://piratejack.net/pbuft5772-1957-72 ... 2-1-4-ton/

When I was was bleeding the brakes after installation, I noticed that the reservoir for the front brakes was in the rear of the master cylinder, and vice versa. This seems counter intuitive to me, but I’m fairly certain I put the lines back where they were originally. Would it make any difference?

[MadMike]

Just one more thing occurred to me. The trouble started just after installing this power brake conversion kit: http://piratejack.net/pbuft5772-1957-72 ... 2-1-4-ton/

That may be part of the problem, 'disc/drum'.
Why did you install a disc/drum MC on a drum/drum system?

Drum brakes require residual valves in the MC to prevent the MC piston from retracting too fast. If the MC piston retracts too fast on an all drum system air will be pulled in past the cups on the wheel cylinders. They will be sucking air. With air in the system there is now compliance, since the driver side(left) is shorter lines it is most likely you are able to compress any air on that side(shorter) enough to make the brakes work better than on the longer lined passenger(right) side.

Wheel cylinders are different for earlier drum/drum systems vs later disc/drum systems.
Since the discs cannot have residual valves in the system as the calipers would drag, and there can't be a pressure differential inside the MC itself, the wheel cylinders needed to have reinforced cups to prevent them from 'sucking air' with an MC that lacks the residual valves in a disc/drum system. It's why you may find two of the exact same looking, same sized, same pistons/hardware, same sized ports and bleeder wheel cylinders but they have a different part number from early 60's to mid 70's. Usually by the mid/late 60's most rear drum wheel cylinders of a same model had the same part number for the rear wheel cylinders.

When I was was bleeding the brakes after installation, I noticed that the reservoir for the front brakes was in the rear of the master cylinder, and vice versa. This seems counter intuitive to me, but I’m fairly certain I put the lines back where they were originally. Would it make any difference?

Drum/Drums were front to front and rear to rear. Disc/Drum switch it around to front to rear port and rear to front port. This is a common/normal setup.

[Cowboysculptor]

My mistake, I linked the wrong part. I actually spent time on the phone with the guys at Pirate Jack to make sure I got a drum/drum MC, they were very helpful.

[Cowboysculptor]

Just an update. It’s finally warm enough to do a little work.

Since I last posted, I’ve swapped the rear and front brake lines at the MC to their correct positions, I replaced the brake cylinder at the wheel, and I replaced the hard brake line back to the distribution block. Bled the entire system. Also cleaned all the parts within the drum and inspected the shoes.

Still veers to the left. Absolutely no change. I’m running out of parts to replace! What am I missing? Anybody?

[Cowboysculptor]

Ignore what this post said previously, I’m a bit ignorant of the workings of this truck. I have a motorcycle background, therefore no power steering. Still working on this.

[Cowboysculptor]

Success! Kinda...

In an attempt to isolate the problem, I swapped the brake shoes and related hardware from the right and left sides. I figured if the truck veers the other direction, then the problem is obviously in those parts, right?

But here’s the thing: when I took it out for a test drive, the veer is gone completely. I hit the brakes hard and everything is rock steady! Fussing with the parts one more time seems to have solved the problem. The thing is, I’ll never know what the problem was. Guess it doesn’t matter now, as long as it doesn’t come back.