1973 Bronco Bump steer

[kphelps]

Wondering if I could get some help? When I accelerate my Bronco pulls to the right a little, when I let off the gas it returns to the left. I have read some of the articles on the website but am not really sure what to do first. I have a lowered drag link at the frame and a lowered pittman arm.

 

[Torkman66]

Could be a few things. I’d first suspect rear axle steer. Does the steering wheel turn when this happens or remain centered? What is condition of leaf springs? Shackles?

 

[Yeller]

A few things come to mind. First are the ubolts tight. Second are the bushings on the leaf springs trashed? If it is only during acceleration and no other time those would be my first looking spots.

3rd, since we know nothing about your rig, does it have a locker or aggressive limited slip? That could cause that as well. But the first 2 will probably reveal the culprit. I’m also assuming you don’t have some fire breathing, crazy horsepower power plant either, that’s another can of worms.

 

[kphelps]

Thanks for the reply. The leaf springs are the only things I have not changed. I have new ones on order from JBG, they should be in in a couple of weeks. Here are some pics of the front steering.

 

[kphelps]

Wondering if I could get some help? When I accelerate my Bronco pulls to the right a little, when I let off the gas it returns to the left. I have read some of the articles on the website but am not really sure what to do first. I have a lowered drag link at the frame and a lowered pittman arm.

I am new fairly new here and don't remember how to post pics?

 

[kphelps]

 

[kphelps]

A

 

[kphelps]

B

 

[kphelps]

I am new fairly new here and don't remember how to post pics?

Figured it out!

 

[Broncobowsher]

That front end looks pretty squared away. Don't see anything glaring. I would be looking at the rear springs as mentioned.

Are the tires the same all around? I once ran over a bunch of nails in the road and lost 2 tires on one side of a car. They put 2 new tires on just one side. I could run a slalom without touching the steering wheel, just on/off throttle. Bad torque steer. Moved some tires around to fix that. That was just the difference between 2 new tires and 2 that had a little bit of wear that you didn't even really notice. Otherwise exactly the same tire.

And am I looking at stacked wheel spacers?

 

[kphelps]

That front end looks pretty squared away. Don't see anything glaring. I would be looking at the rear springs as mentioned.

Are the tires the same all around? I once ran over a bunch of nails in the road and lost 2 tires on one side of a car. They put 2 new tires on just one side. I could run a slalom without touching the steering wheel, just on/off throttle. Bad torque steer. Moved some tires around to fix that. That was just the difference between 2 new tires and 2 that had a little bit of wear that you didn't even really notice. Otherwise exactly the same tire.

And am I looking at stacked wheel spacers?

Tires are the same all around and new. Yes wheel adapters from 5 to six bolt.

 

[Oldtimer]

Looks like you are missing the hose from the front axle vent.

 

[Apogee]

Mine did something similar when I purchased it way back when...replacing the track bar bushings was the fix.

 

[DirtDonk]

How much lift and what size tires?
Power steering or manual?
Stock or aftermarket?
Six turn, four turn, or or three turn steering box?

Why the adapters? Got a good deal on some six bolt wheels?
What width and offset?
You have checked to make sure that the inner nuts of the spacers are still tight?

While the alignment of the track bar and drag link doesn’t look perfectly perfect, they’re not bad and they are closer than most!
Is it a stock drag link? I don’t remember that bend being in a stock one. Possible bent drag link?
If it’s got an adjusting slave at the upper end, then it’s not stock and the bend is common.

I would try taking the steering stabilizer shock off and run around like that for awhile. See if anything changes.
Might get worse, might get better, might not change at all.

Do you have alignment specs on yours? Do you know what the toe-in is exactly?

What air pressure is in all four tires?

Now is as good a time as any to perform the Steering test.
That’s where, with all four tires on the ground, a helper racks the steering wheel back-and-forth about a half turn in each direction while you watch every component at every corner of the vehicle
You’re looking for anything that moves. If it’s supposed to be tight, there should be zero play.
Tie-rod should not rotate excessively when going back-and-forth.
Wheel bearings shouldn’t allow play.
Track bar shouldn’t have play.
Track bar bracket shouldn’t have play.
Steering Box shouldn’t have play on the frame. You get the idea.

 

[Torkman66]

Because you describe this as occurring when accelerating, it is very likely to be rear axle steer. I would not do anything until you get the new leafs installed. Make sure everything on rear axle mounting system is tightened to specs. I also highly recommend the WH heavy duty leaf plate and unbolts. This is the time to do it since you will have it all apart anyway. Then let us know if you are still having the issue.

 

[DirtDonk]

For once, I disagree with Torkman. Now is exactly the time to mess with the other stuff because you’re waiting for leaves and then waiting for time to install them.
In the meantime, it takes a little as 10 minutes to do the Steering test to see if anything else is amiss.
And if you’ve never had it aligned or checked your tire pressures, those are simple, easy, inexpensive things to do in your driveway.
Can easily be done while you’re waiting for the leaves to arrive.

Another very common reason for acceleration and deceleration shifting side to side, is the angle of the track bar.
As already mentioned, yours is not extreme. But the angle does shift the front axle side to side as the front end raises and lowers. So it’s a real thing.
And you may be one of those that has found the Bilstein Shocks to be too soft. For some, they are perfect, for some they are not.
A soft shock with a good ride allows the front suspension to cycle farther for the same input. Thus allowing the axle to shift further for each movement.

 

[JustinPryor]

Wondering if I could get some help? When I accelerate my Bronco pulls to the right a little, when I let off the gas it returns to the left. I have read some of the articles on the website but am not really sure what to do first. I have a lowered drag link at the frame and a lowered pittman arm.

I would start by checking the track bar and drag link geometry before changing anything else. With a drop bracket and a drop pitman arm you want those two links to be as close to parallel as possible. If the angles are different, the axle moving even a little can steer the truck for you.

Also have someone turn the wheel back and forth while you watch the track bar bushings, steering box, frame and all the linkage. Any movement at the track bar mounts or steering box can make these Broncos wander around pretty badly.

Since yours changes direction specifically on and off the throttle, I would also check the rear spring bushings and U bolts. If the rear axle is shifting or rotating slightly under load it can make the whole truck feel like it is steering from the rear. That kind of small movement can throw the whole system off. I notice the same thing with Tropical Casino https://tropical-casino.com/ when a game feels fine until the bet size, bonus mode or session state changes and suddenly the pacing feels different. I’d inspect the rear hardware closely before chasing alignment or steering parts up front.

I would inspect all of that first, then check caster and toe. Throwing more steering parts at it before finding what is actually moving can make the problem harder to sort out.

 

[Torkman66]

Wow I’m actually flattered that DirtDonk suggests “for once” he disagrees with me. I have a small shrine for him in my shop dedicated to the fact my Bronco would never been done without him. So, what he says is your best bet. as he notes, could be a lot of things and the examinations he suggests don’t cost anything. I would not buy any parts yet until you have those leafs installed. But check all you can to see what else it might be.
Your front suspension fit and finish looks great. You might try getting some dirt on it and it will drive better!

 

[73azbronco]

rear axle steer, caused by u bolts not tight, or shackles springs to frame loose.

I just went through this, with all new springs and bushings that had sat 15 years, replaced with new bushings and springs, no more throttle steer. I don't think the springs changed anything, it was the bushings and tightened bolts.

 

[Chiclassics]

May be due to old leaf springs , when you accelerate that puts weight on them more , if they are slights off when it comes their spring tension you will those rotational torques diagonally impact the front end.

Once you change leaf springs
1) do the easy to make sure all your tires are same , with same tire pressure
2) As paul suggested do a steer test. Another easier way to test any bump steer is to push up and down the front end of your bronco and watch if your steering wheel is moving

Then go from there and report back