I've been over this a little before, it somewhat quit after rebuilding t case. Thought i had fixed her on up but seems to be back now, again! sux!

When I let of accelerator after getting truck over about 25-30 mph, a sound pops up and if I give it gas again, it sort of just goes away. Unless I let off again. It's sort of like I can almost control the sound, when I want it to pop up, make it go away, all with the accelerator pedal.
If I'm over the 25-30 that generates the sound by letting off accelerator pedal,(like any speed, 30, 50, 40, 60, etc) and I let off pedal so that the sound will pop up, what happens if I put it in neutral,(while coasting) it goes away. So throwing it into N relieves the sound, gone.
The sound is similar to if you have a stick shift car and you maybe drop it down a gear when slowing down but the gear was a little to low, or like if going in reverse in a stick a little too fast, it's that sort of sound. Not whine, high pitch at all. Not metalish scraping really. It's not deep deep, but a lil close to start to be deep? Hard to describe exactly! I know sometimes when I start truck and put it in R and go to back up out of d way there's a weird sound sometimes for just a min, like a hollow howlish type thing. No clicking on turns, no other sounds really out of ordinary.

Fluid fresh, changed within last 5k. I still drive truck anywhere, runs ex, no issues really. Cruises at 70 down freeway, cc works good, no suspension issues, new u joints over past 2k, tires are 33's and half way worn.

Only things I can remember doing that might be of concern is I rotated the tires back then, sort of before it started. I remember doing that. And I did change front diff fluid. I did not use any of that stuff I used in the rear diff, just oil. In the rear I used a little bit of something I cant remember the name of now, but it's something the dodge mech told me to put in it. Ughhh, I know it needed it but I cant remember the name of that stuff now!! Anyway, I didnt use any of it in the front diff.

Any idea's what this new info could possibly be? How to check anything maybe to rule out? Thanks!!

 

If rebuilding the t-case fixed it before, that's where to start. But when it comes to phantom noises, you'll just have to be patient until it proves itself. One can go crazy trying to find / fix / chase noises. If the truck works fine, keep driving it. Eventually you'll find out what it is or learn to live with it.

 

Well, guess I agree with that. I laid out all the clues I could think of, if ur thinkin to keep on gettin it till something shows, that's basically what I'll continue to do. That's bout what been doin anyway.

I don't think it's t case. Right now the shift rod to the case isn't even hooked up, waitin on the new shift rod kit to get here off ebay. It drives fine without being hooked up right now, got it in 2hi under there at the t case selector.

I've been driving it with this sound for about a thousand miles now. Can't think of many more clues to this odd situation.

I think though that maybe i'll drain that front diff tomorrow, see how it looks in there. Last time y'all said it was possible I had issues with some pinion bearings. Wish there was a way to check those.
The front differential is where I'm leaning if it's not anything transmission related.
The drive shaft is u joints at rear, slip in at the front. There any way there could be something where it slips in at the front of the rear's drive shaft? Anything to check there maybe? There's a seal down inside, rubber where it slides in. But I doubt that's what would cause this sound. Especially when throwing it in N while coasting stops the sound. Ughh. Just sux not knowing some things!

 

Sounds like you're processing the possibilities correctly. Eliminating based on potential causes is good but can make one insane as well. Always start at the cheapest possible component. In this case, as for rotating parts, that would be ujoints. But what you said about neutral is interesting. Is the trans or tcase in neutral? Under what conditions do you put it in neutral? How did you eliminate the sound?

 

Case is in 2hi. Right now it stays in 2hi.
It's in 2hi cuz can't shift t case to anything else right now as shift rod trunnion little piece is broke. Unless i go under truck and manually shift it to 2lo or 4lo. But been driving it around a little lately just here and there in the 2hi. I'm waiting for new shift rod kit to come off ebay, be like 7 more days.

All u joints are new, but maybe I did something wrong when installing them? I don't think so, but never know.
I know the sound started a little after I did the t case rebuild, u joint replacements and change of fluid in front diff. I did all that at the same time last yr. It started after then, but, it was a bit after that, not like right away after.

I can control the sound to coming and going a lot of the time by simply taking my foot off accellerator, once u get over 25-30mph. That will generate the sound. If I give it gas like right after letting off, the sound will subside, so to speak, like go away or go away a whole, whole lot, to barely noticeable but a lotta times it'll just go away all together when giving accell, or gas. Until you let off gas again. BUT, there are those occasions when it can pop up even when giving gas, accellerator. That's sort of rare tho. It's mostly when letting off pedal, pops right up. Sounds like you geared down a stick shift too early, or like you're going in reverse in a stick shift pretty too fast. It's not like crazy loud, but it's def loud enough to where you can't help but hear the thing. It's weirdish!

Lastly, if I'm going and I let off pedal, while it's coasting I can throw it in N and it dies away. Just stops while I'm coasting. When I throw it back in D, there it is again.

It seems like the OD light isn't working right either. OD light comes on only when it feels like it. Like sometimes when I push the OD button in, the light may come on and it'll do the gearing down thing, but most of the time, it doesn't come on and doesn't go out of OD. I worry sometimes when I'm checking the OD that the light's gonna come on, it's gonna be out of OD, and then no matter how many times I push the OD button in it's not go back into OD! You can just push that OD much as you want most of the time and it aint gonna light up and go out of OD. That may be bacause it's not "warmed up" though I read about today. Not all so sure about that though. Anyway, that's just something else I remembered. It's always in OD, from time you crank it till you shut it off, unless you push OD in and even then you gotta keep pushing till it finally decides to light up and drop out of OD.


I think it's something to do with when I changed that front diff's fluid. But that's just a wild guess. Because I also think it's trans cuz of how it disappears when I throw it N.
THANKS!!

 

Well, if it's only happening at a certain speed (i.e. gear) and you can make it stop while coasting by shifting into N, well . . . .

Transmission or torque converter.

 

I'm with ya. Feeling same theory myself. But It's still runnin so good right now, so that I wonder if doin anything else other than another drain and fill might would do for it?
I can def drain and fill again. Been 1 1/2 years since last one, about 6k miles during that time, if even that many! (i don't put lotta miles on it)

Is maybe a band adjustment a good candidate for potentially gettin it to stop makin the sounds? There a sensor, another sort of maintenance procedure or somethin else I should or could do that might be good for it, like before somethin real actually happens? Like real as in real...BAD?
Or think just keep drivin and wait till somethin actually happens, maybe sonething where it don't drive right anymore, then go from there? I feel like there's possibly something I could try at trans other than another drain and fill, as well as the drain and fill though.

Thanks for helping with this, opinions and advice so far! Really appreciate it all! Hope I'm not overlooking something that might could've spared me the "big one" later on! haha.

 

Just a suggestion maybe you are hearing the 4wd shift linkage hit something? Is it just dangling there or completely off?

 

Thanks Fanatic21.
Yea, it was just dangling for past week while was waiting on shift rod for down there to get here.I had it zip tied under there though. It wasn't going nowhere.
Yesterday new shift rod kit came. I put it on, no more zip tied shifter. It shifts great now w that new rod too. Goes into 4lo nice, goes into all cases gears good now.

But sound still there. Can hear it real good when letting off gas after over 30mph. Just get it up to about 30, let foot off pedal, there's the sound. Could be in tranny, but I think could be in t case too.

I appreciate all the help, the questions and suggestions! Thanks!