Odd vibration/rattle from engine (?) on incline in higher gear

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Baba Asheri

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'13 Expy Limited w/130k
I get this weird vibration, rattling sound down in front of my feet mostly at highway speeds, at any sorry of incline, while the transmission is in a high gear. It used to get really bad, so I changed the spark plugs and coil packs at around 128k. The condition improved, but it's still there, but not all the time. There's no drop in RPM when it happens, and the sound remains even after an upshift. It seems to go away only after beginning to decline or by backing off the accelerator. I do have a loose heat shield that rattles even at low speeds, but this sound seems to be closer to the engine compartment. Think it's the heat shield? Or something else? I'm getting no engine lights and no codes. Thanks for any advice!
 

kortensi

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I had something very similar on my wife's 2013 EL XLT, however, whenever it happened, I would see the slightest 'vibration' on the Tach as well. I found a post in an F150 forum to add the following to the transmission fluid: Lubegard Instant Shudder Fixx Transmission Fluid Treatment All 2 Ounce - 19680. I was doubtful after dealing with this vibration for at least 2 years, but it has finally gone away.
 
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Baba Asheri

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I had something very similar on my wife's 2013 EL XLT, however, whenever it happened, I would see the slightest 'vibration' on the Tach as well. I found a post in an F150 forum to add the following to the transmission fluid: Lubegard Instant Shudder Fixx Transmission Fluid Treatment All 2 Ounce - 19680. I was doubtful but after dealing with this vibration for at least 2 years, it has finally gone away.
Thanks! I'll give that a try.
 

eddytheexpy

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Sounds like the IWE system (if you have 4x4) to me. My noises would usually kick off on an incline at highway speeds. It had a slight rumble on the gas pedal and sounded like someone was driving next to me in a pickup with a loose tarp over the bed. As soon as you let up off the gas it went away and would come back intermittently. I rented a brake bleeder kit from autozone to test the vacuum. It didn’t have the right fittings to pull vacuum on the hose itself but I just sorta mashed it in there and it worked haha. But yeah it could be the hose, the check valves or the IWE themselves. You could probably replace all of that for ~$250 and a few beers. However your CV axle might be chewed up from all that gear smashing. I don’t think that job is too bad either but I didn’t need to do that so I can’t speak from experience. fingers crossed for you!
 
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Baba Asheri

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Sounds like the IWE system (if you have 4x4) to me. My noises would usually kick off on an incline at highway speeds. It had a slight rumble on the gas pedal and sounded like someone was driving next to me in a pickup with a loose tarp over the bed. As soon as you let up off the gas it went away and would come back intermittently. I rented a brake bleeder kit from autozone to test the vacuum. It didn’t have the right fittings to pull vacuum on the hose itself but I just sorta mashed it in there and it worked haha. But yeah it could be the hose, the check valves or the IWE themselves. You could probably replace all of that for ~$250 and a few beers. However your CV axle might be chewed up from all that gear smashing. I don’t think that job is too bad either but I didn’t need to do that so I can’t speak from experience. fingers crossed for you!
Thanks for the reply.
So, what you're saying is that a bad IWE component might be slightly engaging my 4WD at highway speeds?
You used the kit to test how the vacuum was/wasn't functioning correctly?
What did you discover on yours that was failing?
You ended up replacing those three parts you listed?
 

99WhiteC5Coupe

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Thanks for the reply.
So, what you're saying is that a bad IWE component might be slightly engaging my 4WD at highway speeds?
You used the kit to test how the vacuum was/wasn't functioning correctly?
What did you discover on yours that was failing?
You ended up replacing those three parts you listed?


When driving uphill, the engine vacuum drops - which can cause an issue with the 4WD system if the IWE (independent wheel engagement) check valve and/or lines are leaking.

If there is a vacuum leak or interruption, the front IWE hubs begin to engage - causing the noise (although you have the system set to 2WD - rear).

There are a lot of posts on this forum about the matter.

The easiest and cheapest part to change is the IWE check-valve, which is mounted in-line with two vacuum hoses, above the brake booster. Easy to access and change.
 

eddytheexpy

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Thanks for the reply.
So, what you're saying is that a bad IWE component might be slightly engaging my 4WD at highway speeds?
You used the kit to test how the vacuum was/wasn't functioning correctly?
What did you discover on yours that was failing?
You ended up replacing those three parts you listed?

yep, when you lose the vacuum it engages the front drive components. But since you’re not totally losing the vacuum the teeth on the outer end of the CV axle are just chewing up your IWE. The cause could be any part in the chain that sees the vacuum so it’s a matter of finding it.

For me, the root issue was a cracked vacuum line that went on to wear out my drivers side IWE. The check valve was fine, I popped it off and just blew into it and it did what it was supposed to (it’s like a $15 part so you could just replace it for fun). The vacuum line was an incredibly easy fix since the new one came with all the mounting brackets already on it. I got lucky because the CV axle didn’t have damage and it just broke the more easily replaceable IWE.

So take the brake bleeder kit and start hooking it up all over the lines to find the leak. As 99whiteC5coupe said, there’s a lot of info out there on the topic. But it’s a matter of finding the root cause since I almost just replaced the driver’s side IWE because I was able to diagnose it as busted but had I not found the leaking vacuum hose it would just wind up breaking the new one too.

Just a heads up, if you do determine it is something to do with your IWEs and not something else entirely, you should replace both IWEs since that means they’ve been getting the snot beat out of them.

Just curious, did the description of a loose tarp at highway speeds ring a bell for you? Haha

This is the hose I bought and it fit perfectly! But be aware it says it come with the check valve but it is only the hose.
 
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Baba Asheri

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yep, when you lose the vacuum it engages the front drive components. But since you’re not totally losing the vacuum the teeth on the outer end of the CV axle are just chewing up your IWE. The cause could be any part in the chain that sees the vacuum so it’s a matter of finding it.

For me, the root issue was a cracked vacuum line that went on to wear out my drivers side IWE. The check valve was fine, I popped it off and just blew into it and it did what it was supposed to (it’s like a $15 part so you could just replace it for fun). The vacuum line was an incredibly easy fix since the new one came with all the mounting brackets already on it. I got lucky because the CV axle didn’t have damage and it just broke the more easily replaceable IWE.

So take the brake bleeder kit and start hooking it up all over the lines to find the leak. As 99whiteC5coupe said, there’s a lot of info out there on the topic. But it’s a matter of finding the root cause since I almost just replaced the driver’s side IWE because I was able to diagnose it as busted but had I not found the leaking vacuum hose it would just wind up breaking the new one too.

Just a heads up, if you do determine it is something to do with your IWEs and not something else entirely, you should replace both IWEs since that means they’ve been getting the snot beat out of them.

Just curious, did the description of a loose tarp at highway speeds ring a bell for you? Haha

This is the hose I bought and it fit perfectly! But be aware it says it come with the check valve but it is only the hose.
Thanks for the further insight and link.
Why isn't the sound always there on the highway on every incline? Typically, it doesn't show up until after an hour or so into a road trip, even though many hills had already been climbed without a problem. Any idea?
 

eddytheexpy

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Thanks for the further insight and link.
Why isn't the sound always there on the highway on every incline? Typically, it doesn't show up until after an hour or so into a road trip, even though many hills had already been climbed without a problem. Any idea?
The description you just gave is almost 100% dead on to what I was experiencing. If I had to guess for my situation, the hose doesn't warm up as like the engine does so with it being a little colder and more rigid the leak isn't too bad. But, after sitting in the engine bay for an hour or so next to the running engine it warms it up enough to lose rigidity and opens the leak more where the supplied vacuum isn't enough to compensate for the leak. So maybe you've got a leaky hose too!
 
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