Sounds more like something to do with the engine in relation to the RPMs. How's your oil level? Do you have an oil leak somewhere?

 

I have something similar happening to me. It actually started when I lowered the truck, before that it had never done it. Probably the same thing though. When I let of the gas, there's this "grinding" noise coming from underneath and you can feel it in your feet, but once you step back on the gas, even the slightest pressure, and it stops.

I'll never be able to pinpoint it though so I don't waste my time. I'll just drive it till something breaks, then I'll know!! hahaha

 

It might be a worn u-joint on the driveshaft. At 75K this is a possibility. The noise happens when you are either loading or unloading the u-joint, and it is not necessarily related to engine rpm. I've seen it happen on other vehicles.

 

Sounds more like something to do with the engine in relation to the RPMs. How's your oil level? Do you have an oil leak somewhere?

Oil level is good because I just put 6 quarts in it last week.

I'd figure it was that except it makes no such noise at any RPM when stopped. When it does begin make the noise it continues until either I hit the gas or when the truck comes to a complete stop.

You can actually watch the RPM on the highway to anticipate the noise though. When it's acting up the instant the RPM drops and the transmission is "loose" from the engine the noise begins and it stops the instant the transmission is locked back up.

It's like something in there doesn't like to coast.

Jon

 

It might be a worn u-joint on the driveshaft. At 75K this is a possibility. The noise happens when you are either loading or unloading the u-joint, and it is not necessarily related to engine rpm. I've seen it happen on other vehicles.

Would it make that noise though constantly while coasting and would a U Joint be a metal to metal scraping? I figured U Joint's would be a clunking or chattering noise like what boat outdrives make. This noise sounds as if the brake rotor was deformed and the pad was worn down to the metal, more of a nasty repeating scuffing sound... at first I thought it was just the sound of air rushing by the truck but I quickly realized it is something mechanical..

The other thing is it's definitely happening the second the engine is disengaged from the wheels and it continues until either I re-engage the engine (by touching the gas) or when the vehicle comes to a complete stop (and then it typically won't return until the truck is brought back up to highway speeds > 60 MPH).. still sound like mabye U Joints?

I'd like to figure out what it is to at least know whether it's worth fixing. If it's the type of thing that's gonna destroy something else or will lockup on the highway then I certainly need to take care of it, otherwise if it's just gonna break or have some operational impact when it "goes" then I guess I'll let it slide.

What's odd about it too is as loud as the noise can be sometimes, it doesn't seem to slow down the truck; you can't even feel it rather you just hear it.

Gonna bring the truck in for a tranny flush.. hoping it'll just go-away but I doubt it .. at a minimum kinda interested in what the fluid is gonna look like.

Jon

 

check the steering shaft too, see if there is play in it

 

It does sound like a U-joint went. u-joints only turn when the driveshaft does...

 

I took it to the shop today; it's my buddies shop where I get a discount and there's a certified Ford and a certified Chevy mechanic there. The Chevy guy went for a ride with me and was quite surprised by the noise stating it sounded like the noise was travelling through the driveshaft (must be a mechanic concept)..

He gave it an inspection, checked the oil and tranny fluid then put it on the lift, checked the joints, driveshaft, front & rear diff fluid, and did something by jacking the rear end up in park and then in neutral (I guess he was checking for rear end issues).. everything appeared to be tip top, no metal found in the fluids and no problem was noted.

He said it could be the torque convertor is failing to disengage properly and/or that it was a transmission related problem which would take him hours to trouble-shoot and that I'd be better off going to either a tranny shop or the dealer.

We both searched through the service bullitens without finding anything noise related that matched.. there are some problems which only happen in reverse or only while shifting or only in neutral but nothing that would happen while underway.

The Ford guy, who's been around a bit longer wasn't around and might have some better input but at this point it sounds like I'm gonna have to bring it to a tranny shop. What I'm worried about is that a $1000 repair could turn into a $2500 repair if I let it run until something really breaks, which were the sentiments of the mechanic.

Still hoping for any input someone may have on a similar problem; if I can determine what the root cause is the cost of repair will be much less.

Thanks,

Jon

 

How can you be worried about a $1000 repair turning into a $2500 repair when you have no clue what needs repaired in the 1st place??

 

How can you be worried about a $1000 repair turning into a $2500 repair when you have no clue what needs repaired in the 1st place??

Well a $1000 repair was just something I threw out there, you are right - who knows.. but a $2500 repair is in the realm of a serious tranny problem (possibly caused by neglecting a fairly pronounced noise that seems to be coming from the transmission )..

My last truck was an s-10 blazer and while running it up to 285K I blew both the front end and transmission (5-spd) by ignoring noises. Now that was a vehicle I maintained with junkyard parts, and it wasn't realy that expensive to fix, but I'm definitely not ready to go there yet with an '06 and even then parts probably aren't cheap as these trucks haven't been around for long.

Jon

 

Well "seems to be" and "possibly" would be a problem in my eyes. lol I just know how much of a bummer it is to throw a bunch of money at trying to find a problem, only to have the problem persist. Pisses me off to high heaven. haha

 

Well "seems to be" and "possibly" would be a problem in my eyes. lol I just know how much of a bummer it is to throw a bunch of money at trying to find a problem, only to have the problem persist. Pisses me off to high heaven. haha

Yep me too, that's why regardless of who is working on it (tranny shop, dealer, or otherwise) I'd like to have a damn good idea of what it is before they go tearing into it.

I just got a call, another mechanic who's more experienced is going to look at it again tomorrow. On another site someone suggested disabling the torque convertor to isolate it (as it's electric).. I'm not sure if it's practical/possible/safe yet but I'm certainly going to run that by him as a potential trouble-shooting step if they again come up with we don't know but "possibly it's the torque convertor".

Jon

 

Well I'll be monitoring this thread for your results. As I said, i've been having something similar happen to me. Best of luck man!!

 

have you tried putting the truck in neutral while driving and seeing if the noise is still there when coasting? this way you would be unloading the u-joints and get rid of that theory. My Isuzu pup does that sound when you coast and goes away under throttle, ends up being the tailshaft bearing has play in it. hope you figure out whats wrong

 

have you tried putting the truck in neutral while driving and seeing if the noise is still there when coasting? this way you would be unloading the u-joints and get rid of that theory. My Isuzu pup does that sound when you coast and goes away under throttle, ends up being the tailshaft bearing has play in it. hope you figure out whats wrong

Yes I have and the sound continues. The only thing that seems to stop it is either stopping the vehicle or touching the gas. Mechanic #1 also spent some time today checking out the U Joints and the driveshaft and nothing was uncovered.

Thanks for the response though,

Jon

 

An update:

Long story short ended up getting reffered to a tranny shop after my mechanic took down my driveshaft looking for another obvious problem which wasn't present. At the tranny shop we took a ride and got it to make the noise.. at that point the mechanic said "I hate #$#@ like this" and explained if it wouldn't do it on the lift it was going to be very difficult to determine where the sound was even coming from.

Luckily we were able to reproduce it on the lift after some trial and error. The technique ended up being to bring the truck up to about 90 MPH in 3rd gear and letting off the gas; as the speed dropped to around 60-70 it made the noise. After reproducing the noise about a dozen times while listening with a stethascope the mechanic was convinced it was coming from the transfer case.

He stated he could easily yank the transfer case and repair it and that it went against the grain for him (as he makes a living rebuilding this stuff and believes that it's the best way to go most of the time) but that my best bet would be to find a low mileage salvage yard transfer case and to just swap it myself or have my buddies shop swap it out.

He said mabye it was a snap ring that fell off or a shift fork which was rubbing on some moving part but whatever the case getting the entire pile of parts out would be a quick simple repair. He stated using a salvage part which he found with 17K miles my mechanic should be able to do it for less than $1200 and stated he'd give him a buzz (they are friends)..

He doesn't know what I actually pay for labor, which is very little, and that my mechanic is a good friend who I trade favors with and charges me cost for about everything. I think he was adding "tax" on the part plus a significant labor rate.. I'm guessing that case could be had for about $600.

Anyway so the plan at this point is to line up a local transfer case and then to take mine off some morning, crack it open, and to determine if my case has an obvious easily corrected problem (like a snap ring which fell off) or if it's a basket case or whether the problem is non-obvious.. if we don't feel like we can fix the transfer case with some level of assurity we'll swap it, otherwise if it's a problem which is cheap to fix we'll just keep our fingers crossed and will give it a try.

Buddies shop is gonna price a case through GM, aftermarket, and salvage Monday to see what cost and availability is. BTW if anyone in North Shore MA or Seacoast/Southern NH is ever in need of an honest tranny guy "Clifford" who owns Reliable Transmission in Peobody MA was the guy who looked at my truck and he is definitely an honest no-BS guy with a great reputation (which is why I was sent there in the first place).

Jon

 

An update:

BTW if anyone in North Shore MA or Seacoast/Southern NH is ever in need of an honest tranny guy "Clifford" who owns Reliable Transmission in Peobody MA was the guy who looked at my truck and he is definitely an honest no-BS guy with a great reputation (which is why I was sent there in the first place).

Jon

Nice plug. He should hook you up just for the free advertising!!