2001 Ex 7.3 4x4 with 4" lift (6" with 37" Pro Comp tires)
All new front end steering components.
All new Shocks (bilstein)
All tires properly inflated to same PSI
All new brake rotors, calipers, caliper mounts, and pads.


When under hard acceleration the vehicle pulls to the left and I have to compensate by steering to the right. Under deceleration the vehicle pulls to the right and I have to compensate by steering to the left.

I am about to change all four brake lines to Braided Stainless Steel lines, replace all leaf spring bushings with polyurethane, and install a rear anti-sway bar.

Any ideas if I'm going through this methodically enough or am I just building a brand new truck one part at a time?

Any helpful thoughts or recommendations are greatly appreciated.

 

Maybe I am off base here, but this is just a theory. During hard acceleration, vehicle nose lifts, and during deceleration, it dives. Your front vehicle alignment changes with height changes. Maybe front end alignment issue??

Another possibility is a bad tire. I only say this because I went crazy one day trying to figure out why a car (not a ford truck) pulled badly only when decelerating. We checked brakes, alignment, everything. It tracked fine at all other times and only pulled when decelerating (pulled harder when brake applied). Just by chance, we did a tire rotation (front to rear) and the pulling stopped.

 

Maybe not off base at all. The truck was recently aligned and within specs. However, it was aligned here in Italy to OEM specs. So that might be the ticket unfortunately I have no idea what the alignment specs are for a lifted EX. Definitely something to think about.
Thanks!

 

Did your lift include a new trackbar to properly center your front axle?

Does the deceleration problem get better/worse when you put trans in neutral?
Maybe only right rear axle is driving and slowing.

 

Yes sir. New Track bar as well.

On the Neutral thing, I'll try that on my way to work and report back.

 

The only thing that I can come up with: Assuming 4WD.... Do you have a lockout hung up in the locked position or engaging when it shouldn't? Might explain the pulling during acceleration, wouldn't explain during breaking, at least I don't think it would. If original or old lockouts, might be worth exploring...

The only reason I suggest: I had a lockout that failed on another truck, the left side and would engage momentarily and intermittently going down the road. You could feel the drag and hear the wine as the left side lockout engaged the left front axle.

Checking the lockouts might be worth your time. A lot of work for my SWAG, but the only thing I can come up with.


Steve

 

Thank you sir. It is 4x4 but I've checked the pull with hubs locked and unlocked but no change. I'll certainly take a look at the hub when I get it on a lift at the end of this week. Certainly worth a shot. Thanks

 

Double check u bolts, shackles, etc. It could be allowing an axle to move some?

Otherwise check the angle between drag link and track bar. Post a pic if you can. If you used a dropped track bar bracket you must use a drop pitman arm to match and vice versa or you will experience bump steer (the vehicle will steer itself as the nose is compressed).

 

Tried placing the vehicle into neutral while at highway speeds, when applying the brakes the vehicle still pulled to the left. Still hacking away at this issue.

 

Get someone to follow behind you and observe, or better yet record video, of how the vehicle tracks as you recreate the problem.

My suspicion is that one of your rear leaf springs is shifting forwards and backwards under load, rotating your rear axle and steering the rear of the vehicle. You have to counter-steer in the front to keep the vehicle going straight but someone from behind will be able to see that the rear wheels aren't directly behind the front ones. Essentialy the tires are pointed forward, but the body is at a slight diagonal.

Based on your description, if it is rear steer, it's the driver's side rear that's shifting forward and backwards. Forward under acceleration, backwards under braking.

 

Nobody has mentioned it yet so I will. Have someone gently rock the steering wheel left and right with the engine running. Both wheels should respond instantly and equally. There should not be any loosness in the linkage or in the steering box. It could be fixed with a simple adjustment in the steering box.

 

Another way to check this is to decelerate to a stop, then get out and measure the wheel base distance. If this is happening, one side will be longer than the other.

 

Yes that is an excellent point, as long as it doesn't shift back once the load goes away.

 

It would not be a bad idea to check your wheel base anyway. If the axles were not set correctly when the lift was installed, it would cause a wheel base error. Check even if you had 4 wheel alignment done after the lift, because they might not have checked wheelbase. Loose u bolts can cause this too.

 

All excellent things to look at.

Steering. Everything is new/relatively new but certainly all replaced from the Steering gear down to the ground.

I'll check the wheel base before I replace the leaf spring bushings and all bolts & U-bolts. I'm hoping to take Friday off and start working the issue then and complete by Saturday evening.

Thanks everyone, this is great food for thought