Man, I have this sound coming from truck when I got home from a small drive the other day. I can hear it AND feel it. It's def in rear. And I'm pretty positive it's from the drivers side rear area.

What happens is this-
When I back up, it makes like this bump bum bump bump bump bump bump sound. BUT, only when I turn the wheels and back up. If I leave the wheels straight, nothing. No sound, no dragging every bump bump bump bump bump while you're going slowly in reverse.
But, when you're slowly going in reverse WITH the wheels turned some to the left or to the right, it will do it. ??

And it also does when going forward, slowly as well, with the wheel turned to left or right. But NOT if I just keep wheels straight will it "drag" so to speak, bonk bonk bonk bonk bonk, until you stop. Only in the rear, only with wheels turned.

Thanks for any expertise on this one! Man, this is a little complicated figuring this one out!

 

It's like something's binding. It sort of feels like a dragging for a split sec, then stops for a split sec, dragging for a nano second., then stops for a nano second, all while youre backing slowly out of drive way and going slowly back into driveway. Over n over.

Hard to explain. Shoot! It's like a bump bump bump bump bump over and over the whole time you're slowly moving until you stop. Like something's trying to hold it. Like, it's just hard to describe. I hope you know what I mean.

Thx again!

 

Time to pull the cover, and see what you find. Stop driving it for now.... else you may end up with a grenaded rear end.....

 

Ok. So pull the diff cover? I just pulled the rear diff cover last week, changed the fluid in there. Didn't see anything going on in there or in the fluid that came out.
But that's prob not the cover you're talking about back there?

Why would having the wheels turned affect anything at a rear of a truck, while I'm moving in reverse or easing forward? Soon as I start moving in reverse, backing out of the driveway, or, going forward back into the driveway, it does it like 6, 7, 8 times during each revolution of the tire. Like every 2 secs it clumpsthumpsdragbitesgrabs, instantly, and does this noise over and over for as long as you want it to.
Theres no movement similar ball joint trouble, not that I can tell. When I jacked it up and did the 12 oclock-6oclock test, it seemed to pass that. And the 9 and 3 test. But who knows. Could it be anything with the braking system back there?

Whatever that thumping/rubbing/clunk/scrape sound is what I can't figure out. It's like something is pushing at the brake or like somethin is grabbing at it every 2 secs real quick while easing backwards, or forwards(but ONLY if I got the wheels turned)

And why would it NOT make the bumping thumping scraping type sound what so ever, when I back up or go forward with the wheels STRAIGHT?

Ughhh. This sucks not knowing. Maybe a bushing? Some type of support cross bar?

I don't really know which cover to take off to look inside yet. The rear end pumpkin part?
Thanks again for y'alls guidance/help!

 

Yes, HeyYou is saying to pull off the rear inspection cover off the rear end, the same one that you pulled to change the fluid. When you changed the fluid, what type of gear oil did you replace it with and did you fill it to the proper level?

I would also pull each rear wheel and check the axle bearings. See if you can move each axle up and down or side to side. If no excessive movement, those should be fine. Also check for oil leaks at each wheel, too.

 

While you have the rear wheels off, check the brake mechanisms too.

 

Sounds like either the front is binding slightly when backing up, or the limited slip clutches are coming apart in the back.

Quick test for the front would be to jack it up and turn it to full lock then spin the wheels by hand both ways, then turn to the other lock and try it again. If there is any binding try to find it. Probably the u-joints on the axle.

If the front is free, then jack the back up and see if there is any binding just spinning by hand. If it is a bearing going out this could show you which side it is. If this checks out good, then I would open the diff again and see what's happening.

As was asked already (maybe I missed the answer) but what oil did you use, and if a limited slip rear end, did you add the friction modifier and enough of it?

 

Yes sir, Frankie b jr! The truck did seem to be binding a little bit the other day at the FRONT. The left front wheel. But, why should the noise/bind/thump sound, that bump, bump, bump, bump, bump as your backing slowly with wheels turned so to simulate a half moon, and slowly forward as well, why would it seemingly be happening at the REAR?? Is it trying to trick me or something? Seems you can hear it from the drivers seat back there at the rear though, and from standing outside while someone else backs it up slowly.(I think, but now I just dont know!)

I know for a fact, the other day, I did hear FRONT wheel make what seemed to possibly be an issue up there! Some new noise it made while she was backing slowly for me with the wheels turned to the left, while I was at the rear listening to try to pinpoint the location of the regular problem noise. She probably did have the wheels turned pretty far left though but it made some sound a couple times up there.

That fluid change was with this stuff: It's the Valvoline Syn Power 75W-140 full synthetic gear oil(1 qt). I filled to the plug hole and capped it. (bought new cap)

Now, as I read the reviews about this fluid, one guy asked about the Ford Explorer AWD he had. He said it required an lsd modifier as the Explorer was a 1998, said the book told him to put it in his diff. He asked Valvoline was it


good for his vehicle. Their response was this-
"The SynPower 75W-140 does contain a small amount of limited slip additive already blended in it. However, it is not enough for your Ford Explorer. Valvoline recommends adding an additional 4 ounces of limited slip additive to the differential at the time of service."

Not sure what that answer to his ford question is telling me though, as I'm not even sure the noise is actually the rears diff or even sure where its coming from anymore(the front or the back!).

I'll def do the next set of tests/trouble shooting recommendations that HeyYou, AtomicDog, dbbd1 and the things frankie b jr said to do! No problem, will get on it as soon as home from work!

I'm wanting to drive my truck! Just not so bad that I create an explosion simulated to a grenade as HeyYou pointed out could happen. That I was to find the problem 1st. Fix it. THEN I can drive her again! So, will do, and thanks for y'alls assistance. Invaluable!

 

Does your truck have an LSD rear diff?

 

Hi HeyYou. Yes sir, its a ltd slip I believe. I'm pretty sure anyway. When jacked up, in park, the wheels do NOT turn at all. Should I put it 2 Lo and check maybe? Thx.

One thing frankie b jr wanted me to check was for binding at the front. He says,

"Quick test for the front would be to jack it up and turn it to full lock then spin the wheels by hand both ways, then turn to the other lock and try it again. If there is any binding try to find it. Probably the u-joints on the axle."

So, when he says full lock, he means 4wd Hi on the floor shifter and neutral at the column, or leave it in park? Really, I'm not sure what to do there. And "the other lock" means like 4wd lo maybe(again, I dont know what to!)

Then, if there's anything tryin to bind it, I'll finally know something! Like the u-joints on the axle may have issues? And that could possibly be the noise, the bum, bump, bump thing while moving backwards slow with wheels turned?
At least I'll finally know something to get this ball rolling! For a change!
We did find if it's ltd slip now too. I think anyway! The wheels wont turn in park, no way no how! That mean ltd slip? The rear's jacked up still, if I need to try somethin diff to see if it's ltd slip, let me know and I'll go out there right now!
THX for helping.