Hey everyone, I've been having problems with my 98 F150 shaking intermittently at mostly freeway speeds. Sometimes I can drive 65-70 no problem, sometimes I can barely get to 50 without it rattling the whole truck apart. Definitely been a head scratcher for me since it started. I'm leaning towards transmission issues, it's been giving me problems lately (occasional slipping, hard shifts etc.) When braking, it seems to "drag" in certain spots as well below 10 MPH. Either that or it could be driveshaft u-joints. Brand new tires, less than 1500 miles on them. The truck is a 2WD 4.6 with a 4R70W. I'm just wondering if anyone here can give me some tips on where to look.
Have a great day everyone.

 

A couple places to check:

• Plugs and COPS/Wires (tune up)
• Dragging brakes
• Wheel balance

Are you experiencing any check engine lights? Have you put a code reader on it?

Also, how many miles on your truck?

 

Use an infrared thermometer to check the brake temperatures after driving it to eliminate the brake dragging possibility.

 

The truck has 240k on it. I used Forscan to find out that the passenger side O2 sensor before the cat is bad, the new one got here the other day and I'm planning on putting it in once I get the chance. No check engine lights other than the sensor. Dragging brakes is a possibility, sometimes when it gets up to temp it seems to get held back when I let off the brake at a light, I have to give it some gas to actually go. I'll have to get an IR thermometer to check the temps. I just had all four wheels and tires balanced as well.

 

Did you have this problem before the new tires ?

Check your parking brake to make sure it is fully disengaging

 

I'd bet on brakes sticking, most likely the rubber front brake hoses are collapsing. Been there done that on mine. You don't necessarily need a thermometer, just feel your hubs with your hand.

 

The problem began before the new tires, it just wasn't as pronounced. The parking brake is in the rear drums right? Next time I drive it I'll have to check the fronts to see if they're sticking and make sure the parking brake is releasing properly. I'm out of state right now but once I get back I'll take care of the O2 sensor and check out the brakes.

 

Forgot to mention that recently I've noticed that the brake pedal will sometimes get hard too. Not sure if the drag happens at the same time or not. The pedal getting hard tells me to look more at the rubber brake lines too though.

 

Classic symptoms. Replace both front rubber lines and bleed the system. Take care of it before you destroy the pads and rotors.

 

That'll be the first thing I'll look at once I get back then. Both rubber lines going to each front caliper right? I'll search for good motorcraft replacements. (Skimped out on non-motorcraft parts once before, never again)

 

Something you might want to consider - at least after chasing a "shake" similar to the one you describe for what seemed like years on my '99 f150. And this was after at least two sets of new tires (all four), alignments and re-alignments, balances and rotations, and even putting on a new set of steel wheels. In brief, somewhere around 150,000+ miles an intermittant 'shake' would come in at speeds anywhere between 50 - 75 mph, on any type of road surface - though it was more noticable on new pavement.
In the end, at 312,000 miles, I decided - as a last resort - that I would have a full / complete front end rebuild - everything - all of it, new control arms - uppers and lowers, new bushings anywhere there were bushings, new end links, new ball joints, new KYB shocks, new discs / rotors - all of it / everthing. Did I say everything? It was also at this point I had new tires and new steel wheels put on. Long and short, the new front end (rebuild) was the cure. I could go on about how old I am and how many years I've been driving, and how many types of rigs I've owned, but that would just be boring. I had a hunch, considering how old the truck was and how many miles it had on it, that this step was the most logical - though expensive, yes - to take. In a word, it simply worked. My '99 rides like new - engine doesn't have the same pep it did when I drove it off the lot, but when it quits, I have dreams of putting in a Coyote engine . . . .
Anyhoo, good luck with yours.

 

I hate to revive a thread, but I figured this was better than starting a new thread to continue this one. I got back home and decided to make 100% sure the rubber brake lines were collapsed before replacing them like glc suggested. I jacked up the front end of the truck and pumped the brake pedal many times but no luck, the front wheels never showed any resistance as if the brakes were stuck applied. Now I'm a little lost. I'm not completely ruling out the brake hoses, but now I'm a little less focused on them.

 

open the bleeder valve and see if fluid is moving through the lines. If it is then your calipers are frozen. If not then your lines are blocked.

 

I'll have to check out if there's any fluid from the bleeder. I noticed that recently if I press the pedal halfway down or more the front end shakes really bad, making me think the front rotors are warped. So you may be right, the calipers could be frozen somewhat.