Hey everyone,

I have posted much on this site but have used several posts to continue to improve my 2002 F150 FX4 lariat scab.

As it relates to suspension, this was my brother's truck until May of this year. it was garage kept, babied, etc. But only work done to it was when something broke (other than oil changes, tires, etc.).

It had the original "Rancho" shocks on it because of the FX4 and heavy duty payload package. all of that was still stock but the tires which are Michelin defender LTX's. Their balance and runout have been check and all within rage.

General Symptoms:
- feels like wheel bounce at different speeds (especially around 45MPH)
- if you go over uneven road at highway speed, you better be holding on to the steering wheel as you will get a jolt
- many tiny vibrations when going over a speed bump at faster than turtle speed. From this point forward I will call it a shimmy.

- First thing I did was replace all four shocks with KYB gas-a-just ones specific to this vehicle. The ride was better but still had bouncing at certain speeds and shimmy'ing when going over speed bumps (both front and rear).
- Took it to a mechanic I trust and the only thing he foundwas a worn out sway bar end link bushing so I replaced both with MOOG branded links. He also check the tension bars and they were set correctly. He could not find anything wrong with the other suspension components as there was no play at all. He did notice that the Steering box could be moved slightly when using a pry bar and lightly lifting it. Haven't done anything with that yet.
- However, still get way more bouncing that I would expect as well as still the shimmy over speed bumps.
- Being the OCD person I am, I went and bought new Rancho RS5000 shocks for the front b/c honestly I am think that the front end was overpowering those KYB shock even though the are correct for this truck (even contacted KYB on this). The ride is definitely different now and I think toward the good. It seems to be a little more planted but kind of hard to tell. I still get a very very slight shimmy (almost nothing) when going over bumps with the front tires and still the massive shimmy when going over the speed bump with the rear tires.

A little tired of throwing money at the problem not knowing what is going to fix the issue and this is where this group can help me.

So, what do I do to continue to troubleshoot my issues?
- Thinking of purchasing Rancho for the rear and see how they do. Thoughts?
- Even though all of the suspension components seem to be tight, are some worn out?
- Is the steering box a bigger deal and potentially the root of my problems?

Can anyone relate and/or give direction on next steps here?
Happy to answer more questions if that can get me to resolution sooner.

thanks,
rodney

 

How many miles on the truck? At around 130k miles I had to replace the lower ball joints, front bearing hubs, passenger side rear axle and bearing, tie rod ends, idler arm, and sway bar bushings. I never had any vibrations though. I was running Michelin P metric tires and getting them balanced every 10k miles or so. I also replaced all 4 calipers, all 5 flexible brake lines, and master cylinder to get rid of brake overheating issues.

 

Thanks Roadie. I have 112K on it Tires only have 7K miles. I do get pulsing when stopping so I am looking to do the calipers, brake lines and master cylinder at some point. But honestly, if I cannot figure out this suspension issue, it makes me no want to put more money into it. I have occasionally put it into Neutral going down the road and I don't really feel the brakes dragging, so maybe I have some time with that.

Could it be the steering box? However, I don't get hardly any vibration through the steering wheel though.

When you made all of those changes, did you ride change at all?

 

Drove the truck today on the interstate. I stretch I have run several times with the KYB shocks front and rear. It does have some rough patches so was a good test. The Rancho's in the front did so much better with control when going over rough parts of the road.

So much so, I went ahead and ordered some Rancho 9000XLs. I pull a camper and boat occasionally so having the adjustability can be good.
I will report back once I get them on and a few drives with them.

 

I think I would go to a different shop and get the tire balance checked just to be sure. Our vintage trucks are notorious for warping the rear brake rotors. If you buy cheap they will warp in no time. Buy only the best brake rotors for the rear. That is what gives the pulsing when stopping especially if you feel the rear of the truck moving up and down. I bought Autozone's best rear brake rotors and they warped in about a 1000 miles. I haven't replaced them yet but they are annoying and I will replace them.