I've got a rattle in my truck that's about to drive me insane. It only happens when I'm in 5th gear, between 50-60mph and between 1200-2000rpms. Sounds like marbles rattling in a tin can kinda, very metallic. It sounds like it's right under my feet.

My mechanic, who I trust, recommended an exhaust place because he thought something was loose and would need welded. The exhaust place kept it for a day and a half, welded a small unrelated leak near a catalytic converter for free, and said they couldn't figure it out either.

The exhaust guy suspects that I've got a leak in my vacuum line for the 4WD and when the engine is at those low RPMs the hub is trying to engage. But he said he couldn't find a leak and that was just his best guess.

I don't notice any difference in driveability when it's rattling and if the radio's turned up I wouldn't even know it was happening.

I'm not a car guy and certainly no mechanic, but surely somebody here has had a similar rattle or an idea of what the problem might be.

2007 F-150
Extended cab
4x4
Automatic transmission
5.4 V8

Cat Converter?

On/off the peddle? How do you get 5 speeds out of a four speed trans? 1200-2000 rpm would be more like 30-70 mph? Is it a shudder when the clutch engages/disengages? Any codes? Wish I could help more, but all I get is more questions. How many miles? Bad u-joints in the front drive line, hub bearings, transfer case?

calikoolnic asked good questions.

Does it occur under thrust (does it stop when coasting or when trans in neutral?). If it's something worn/loose in the drive train (maybe a carrier bearing or u joint given the location you describe) it should change when not under thrust - but those components usually sound deeper when going out - a rumble more than like marbles in a can - and will do it in any gear.

If it's something blowing around in the cat conv it could stop when engine is at idle or off (as in when coasting).

If you think it is a vac leak causing the 4wd to try to engage, go ahead and engage the 4wd and see if it stops.

If the noise does not change pitch/volume with change in rpms or speed, it's probably an accessory rather than a component in the drive train.

Maybe just keep the radio turned up loud and, when the noise gets louder than that, you'll probably be able to tell what it is.

Is there kind of a ringing sound to it in addition to rattling? Bad torque converter in my 99 F250 powerstroke made a noise like that. Very well known issue with 99 and 2000 Ford Super Duty trucks with the 4R100. I know that's a different trans than what you have, but it may be worth looking into the torque converter.

Bingo!

That sounds like the problem indeed.

I had a 2007 SuperCrew 4x4 F-150 that did the same thing. Drove me nuts too...

Let me explain what happens when you get a vacuum leak in the line that controls your front hubs. The vacuum line doesn't "engage" you front wheels, it rather keeps the hubs "disengaged" until you turn the knob to 4x4. The vacuum holds the actuator gears away from the lock system. When it has a leak, the gears slightly engage and start grinding slightly.

It's a pretty complicated mess, and the sooner you get it into someone that can work on drive-trains the cheaper you will get off.

If I remember right, I needed a new actuator and the vacuum leak fixed. (That vacuum line was hard plastic and had a hairline crack in it.)

The bill was $300 and change. It would have been way more at the Ford Dealership though. Should solve the mystery for you though.

Torque convertor?
When the rattle starts, push in the tow haul switch.
Does the noise go away?

I've owned many ford trucks and each and every one of them developed a rattling similar to what Blue is having and each and every time it was a heat shield around a catalytic converter or other exhaust component.

To add to what I already said... That noise will get progressively worse, and turn into more of a "grinding" noise as the gears of the hub and actuator grind off. For some damn reason the actuator gears are made of brass, and after they are ground off from the end down, they need to be replaced. There is one on each side, but the vacuum leak probably only affects one side.

That is why you think the noise is right under your feet.

If you increase the RPM's it may stop because the higher RPM's create more vacuum. Less rpm's less vacuum, and the noise starts again.

This started on mine at about 150k miles. Let us know what the problem actually is.... My mechanic had checked the heat shields first. I'm sure your exhaust guy did too.

Sounding as though it's right under your feet, I'd say the catalytic converter. I had one go bad on a Silverado that about drove me batty. I took a rubber mallet and lighted hammered the exhaust and as soon as I tapped on the converter...bingo.
The IWE''s (inner hub) can go bad and give an unpleasant sound. I helped a friend fix one not too long ago. We were suspecting a vacuum leak but it was just one of the seals failed on an IWE.

take ya some long self drilling screws and run up in that P O S converter, holds the insides that have broken loose tight. no more rattle done it on everything from jeep commanches to ford super duties works for em all

It sounds like your mech's right. Those aluminum heat shields seem to rattle or rust loose after a few years. Pull it off and drive on.

I'm gonna try to answer all the questions at once, let me know if I miss something.

OKOK-I don't think it's a cat. I had a code several months ago and replaced a cat and haven't had any problems since.

calikookinc-It's my highest gear, I assumed it had five gears I've never counted them. It only happens when I give it the gas, let off the gas and there's no grinding. And it only happens when I'm lightly accelerating. If I accelerate quickly from 50-60 there's no rattling noise....but that's also because I get out of the RPM range too quickly. It'll only happen between those RPMs and speeds. Imagine if you're going down the road, accelerate to your highest gear, then have to slow down a red light-that turns green as you approach so you start gently accelerating again. If I hit 2000RPM or 60MPH it goes away, every time. No shuddering and no codes. 144K miles. No other problems with the front end or drivetrain that I know of.

CCCC-No rattle when I'm coasting or idling. There's no change in the pitch or volume to the rattling. Since it only happens between 50-60mph I can't throw it into 4WD to see if it stops.

Fortymile-No ringing.

LRoy-I haven't tried that, but I will try it tomorrow. We plan on taking it to the lease.

Bruinrun/Tzone-So if I take the heat shield off, does that cause any problems?

Rockinbbar-Here's my question about the vacuum leak. If it's rattling because there's not enough vacuum pressure and stops rattling when I give it enough gas...why does it also stop rattling when I let off the gas to coast? It seems to me that if the problem was a vacuum leak due to not enough pressure it would DEFINITELY rattle when I was coasting. But I don't know.

Thanks for all the help guys, keep it coming.

My initial reaction is to just not accelerate slowly from 50-60mph, but if there's something wrong I'd like to know...kinda.

Blue, I never noticed any issue when a heat shield fell off, but I wasn't towing with these vehicles regularly, either. I've seen where guys have used large hose clamps to snug up a vibrating/ rattling heat shield instead of removing the shield or letting it fall off.

You might try this little experiment. With the truck running and warmed up and the trans in park, slowly bring up the RPMs and see if you can get the sound/vibration to occur. If it does, it isn't in the driveline and my money would be on a loose heat shield.

Good stuff here from some sharp folks.

I am not a Ford guy, so can't provide anything specific to that truck, but sounds like you had better eliminate (or fix) any 4wd engagement issue quickly. Those hard plastic vac lines can be a pain - they develop tiny cracks that are hard to see/find.

You don't have to engage the 4wd at 50mph - just engage the 4wd at idle and run the truck up to the speed/gear where the issue is occurring. If the noise still is there, it is not the 4wd trying to engage and grinding.

If you don't want to do that, disconnect the vac line to the actuator - if noise stops - that is your issue. If not, be thankful and go after those loose/vibrating possibilities these guys mention.

Nice to see so many helpful folks here.

Blue, did you ever get this issue threshed out?

I thought all Fords rattled.

I'm with Mickey. If I was driving a Ford (no) that didn't rattle I would be very concerned.

Just turn the dang radio up and drive.

Mine was making a strange noise like two skeletons making love in a tin garbage can,tail pipe rattle.

Dumb question but does it have adjustable pedals in it ?
If so there is a service bulletin from Ford about them rattling at times.

Also if it's got an overdrive on/off switch on the gear selector, what happens if you turn the overdrive off ?

Only proof it's a Ford!

If you have an IWE issue(4x4 hub) and you can't put it in 4x4 at that speed just unhook both vac lines at the hubs, this will engage them and just drive the truck to see if the noise goes away. If the noise is gone one of your hubs is grinding. There are a lot of things that can cause this so don't just throw hubs on it until it's diagnosed. I'm a tech at a Ford dealer and I deal with these all the time. I've seen lots of bad solinoids, check valves, bad vacuum lines and IWE's so any of these can cause hubs to grind. PM me if you need any help with this, I know the system like the back of my hand.