Hope you guys are having a good memorial day weekend. I'm chacing down a rattle, and I'm about to take it to a mechanic as I don't want it to be anything serious.

Anyway, 1998 F-150 5.4.

I jacked the rear-end up and couldn't find anything, I greased up the U-Joints thinking maybe it was them. There is no play in the driveshaft and seems pretty sturdy. After I finished with that I took it for a drive and the damn noise is still there.

Only happends in drive. The rattle appears when I begin accelerating up until about 25-30 MPH then it goes away. As you speed up the rattle gets faster then seems to dissapear, well until you stop and it does it all over again.

Any help is appreciated, I'd rather not get gouged at the mechanic.

Thanks guys.

 

where do you think the rattle is coming from?front...rear...midship? only in drive under load? check all the mounts...does it do it in neutral going down a hill when you reach the speed? more info is good...happy memorial day weekend to you and yours...zap!

 

It appears to be coming from the front. The truck doesn't even have to have load at all for it to happen. I just take off normally and it happens, rattle gets faster as I accelerate then finally dissapears. It's definately a metal to metal rattle. When I'm pulling into my driveway with my foot off the gas I can hear it rattling a little bit.

When I had the rear-end jacked up, I started the car and put it in drive and there was no rattle.

After hours of searching the forums I'm thinking it might be an exhaust clamp or something, but if it was an exhaust clamp one would think you could get it to rattle when in Park giving it gas, which does not happen. I don't know what to think, probably just take it to the mechanics.

Any more information is appreciated, thanks guys.

 

if you "stand on it" and it goes away i'd look at the u joints...greasing a bad one will not do anything..do you have a vibration anywhere when this happens?

 

zapster- Do you ever work on ANY F-150s.

 

no i dont i have a '99 350 diesel duallie dump...need the windows up its loud...but the stereo works just fine ...zap!

 

What exactly do you mean by "stand on it"?

Thanks for the reply's guys.

 

stand on it means put it in drive and stand on the gas pedal..plant your foot to the floor thats "standing on it"...zap!

 

Does it sound like a tinny rattle or more like a washer jingling on a bolt?

I've got a couple idears.... let me know.

-Joe

 

Joe, what's up man. It sounds like a washer jingling on a bolt. Like I said when I accelerate the rattling gets faster until finally it just stops when I get up to a certain speed, 30ish MPH.

I'm thinking about jacking the front up in the days coming, so any of your ideas would be appreciated so I can look for them when I get under there.

 

That's what I wanted to hear. The fix is much simpler than you would imagine.

Remove the center cap on the front wheels. You'll see a cotter pin and a retainer for the nut. The retainer has a small bead of silicone from the factory that tends to harden with age. The jingling you're hearing is the retainer slopping around on the shaft. Use a pair of side-cutters to straighten the cotter pin and pry it out. (If you're careful, you can re-use it. It's a good idea to replace it if you can) Remove the retainer and put a good sized bead of silicone or blue RTV around the edge where it'll make contact with the nut. Smoosh the retainer back on, re-insert and bend the cotter pin and put the center cap back on. Repeat for the other side.

I had the same problem for a year before I found it.... was driving me BATTY!!!

-Joe

 

u-joints don't have to be loose to be bad and grease will not fix a bad u-joint. i had a u-joint problem on my truck for over a year and everyone i went to told me the u-joints were good because the driveshaft had no play in any direction.
the noises and vibration eventually got so bad that i took the driveshaft off myself and found that the rear joint was so tight i needed to hit it with a hammer to move it in either direction.

 

GIJoe has an idea there, but I'd be more apt to think it was an exhaust shield rattling. A shield rattle sounds EXACTLY as you are describing. Get under the truck and check the shields around the cat and anywhere you can see a shield against the body. They will typically make noise in a certain RPM/sspeed range and then disappear.

Also, to try and isolate a shield rattle, put the truck in drive and then rev it up a bit while holding the brakes. If it's a shield rattle, you should here it...

Give that a shot....

 

If it's a tinny sound, then yes, it's likely a heat shield, but most heat shield noises won't be restricted to when you're moving. They'll happen at idle too. Heat shields are a tinny rattle, not a washer jingling on a bolt sound. The sound disappears at around 30 MPH because the centrifugal force is strong enough to stop the retainer from flip-flopping, holding it off to one side. I've been down this road before myself. I'm easily 99% sure that's his problem. There was a rash of them with this problem about 5 years ago. We're about due for another wave.

-Joe

 

Alright Joe, your theory proved fruitful but only solved half of the problem, very thankful nonetheless. I owe you a case of beer.

The passenger side cotter pin was rubbing the center cap causing the metal to metal sound when I wasn't accelerating just rolling. So I took out both cotter pins drivers & passenger side, used RTV silicone to grease up the retainer nut, and slapped everything back together. I took a drive w/o the center caps on, the metal to metal sound is gone, but the rattle is still there.

Although, I have some new information. It could quite possibly be a drivetrain component. It still rattles at small acceleration but it appears to rattle all the way up until first gear winds out. So, when you give it a little gas it starts rattling, then it gets faster as first gear winds out, then right before it shifts into second the rattle stops then shifts into second gear and it's quiet.

Revving in park cannot re-create the rattle, and FYI I have a high-flow cat, and I've checked it, it's not rattling nor is the heat sheild.

I appreciate everyones help thus far, and thanks again Joe it's half-way fixed.

Justin.