Slight rumble/vibration coming from drivetrain on acceleration..what is it?

[Thallarsen]

'99 5.0 AWD with 210k. Good tires/brakes/shocks/exhaust.
Nothing loose.
I'm starting to notice a slight groan/rumble/vibration that reverberates up from the drivetrain on acceleration - particularly under load, or up a hill. More noticeable accelerating from a stop or moving slowly. It sounds/feels like it's coming from the rear. It's not a constant 'crunch, crunch' like wheel bearings, & I don't hear it when not accelerating.
In previous cars, I recall this sound/vibration as a result of bad u-joints, so I replaced both (I have to say that I was amazed that both original u joints were in decent shape/still had grease).
No change after new u joints.
I'm guessing a bearing/bearings in the rear diff.
Any ideas?

 

[FIND]

Also check your exhaust and make sure the heat shield is not coming into contact with it or that no part of your exhaust is coming into contact with anything.

 

[Thallarsen]

Nothing to do with my exhaust. It's the rear diff, I'm pretty sure. Curious as to what tends to go in these that would fit the noise description.
Are there any serviceable bearings in the axle housing w/out having to pull the entire axle, or am I likely looking at a junkyard axle?
V8 - D4 3.73 LS rear, BTW

 

[my pos mounty]

Its most likely the clutch packs in your limited slip differential. It would "shutter" and have a little vibration that would reverberate thru the drivetrain. You would feel it most when accelerating from a stop and turning at the same time.
You have to remove the differential carrier from the rear axle assembly and disassemble it, then replace the clutch packs. Recommend stacking them in a slightly different manner.
Heres a thread on the mustang forum that can guide you thru doing the job, but bear in mind that the referenced thread is a total rebuild of the limited slip differential. You won't need to do all that, just enough to get to the clutch packs.
http://www.allfordmustangs.com/forums/5-0l-tech/118464-how-rebuild-your-8-8-rear-end.html

Take this time to inspect all your bearings and replace them if needed.

 

[jremington59]

Are you sure that your tires are all the same? Is there one worn down more than the rest? I just bought new tires and one of them was faulty from the company and was causing the differential to be working constantly. At 3/32's difference in tread the smaller tire will have to turn 8 times more per mile than the other three. The vehicle senses this and shifts the power to the tire turning more thinking it's losing traction. At least that's close to how it was explained to me, lol.

With the AWD it doesn't take much. Do you also hear a whining noise?

 

[shane0613]

My 98 AWD Explorer started doing the same thing after some idiot ran into my front drivers side and pushed my vehicle to the right. I was at a complete stop when he hit me and he was going maybe 5 mph, but he didn't stop immediately. I thought it might have been out of alignment so I got it aligned and it didn't solve the noise. I have yet to figure out what is causing it. My drivers side front tire is wearing down on one side pretty badly. I took it to a place called Doug's Auto in Conway, SC and he charged me $180 to align it after originally quoting about $80. Said he needed 2 camber kits to align it, and a few months later and the new tire is wearing out. I think I got ripped off, and they also didn't have any idea what the noise was coming from.

 

[my pos mounty]

Since yours got smacked in the front, I would be seriously checking and rechecking the wheel bearing/hubs, the CV's and the front differential. You could also have a bad balljoint or tierod that would cause the irregular wear on the front tire. It could have deteriorated after the accident but was not "gone" until after the alignment.

 

[Thallarsen]

I doubt it's tires. It's most apparent when under load. Although not speed related, there's more load when accelerating from a stop. That's when it's most apparent. Turning or straight doesn't seem to make a difference.
I haven't taken any kind of hit that would cause an alignment issue. This has been coming on very gradually. I'm thinking that it's some kind of bearing in the rear diff. This truck has 210k on it, so something like a rear starting to go wouldn't surprise me.
Anyone know what the signs of pinion bearing failure are? How to test?

 

[my pos mounty]

My last post was addressed to shane0613, I probably should have prefaced it that way.
As for your symptoms, they certainly do point more to bearings more than clutch packs as I previously stated. I thought you had more of a "chatter" happening when you took off from a stop or when accelerating from a slow roll (clutch packs).
I had a similar condition to yours, except mine developed quickly into a loud whine that made it near impossible to talk in a normal voice with a passenger. I replaced my rear axle assembly with a junkyard unit. (total cost under 300) I replaced the axle seals and double checked the condition of the bearings before the install. Hopefully this will last me awhile.
There really isn't any way to test from the exterior of the diff other than taking out the rear driveshaft with the rear of the truck off the ground and turning the driveshaft flange. If it feels "chunky" or has movement, you found the problem. Other than that, you would have to open it up and take a look at the bearings. You might be able to see gold flecks in the fluid, if you do, your bearings are junk.

 

[Thallarsen]

mounty,
It is more of a lugging vibration that increases under load - as opposed to a chatter. Whatever it is, it isn't making the car undriveable - at least at this point. I suspect that it will worsen and it sounds like a junkyard donor is the way to go. Of course I need to confirm the proper ratio, but is a non-LS an option? You were able to get a decent D4 for $300?
btw, when I mentioned not taking a hit, it was also a reply to Shane's suggestion. A good one, but not the case in my situation.

 

[my pos mounty]

mounty,
It is more of a lugging vibration that increases under load - as opposed to a chatter. Whatever it is, it isn't making the car undriveable - at least at this point. I suspect that it will worsen and it sounds like a junkyard donor is the way to go. Of course I need to confirm the proper ratio, but is a non-LS an option? You were able to get a decent D4 for $300?

No, not just the replacement axle assembly. I completed the whole job myself, with new axle seals, new cross pin locking bolt, 4 new U-bolts, Ford differential fluid, Ford friction modifier, the RTV sealent and 3 cans of brake cleaner for under $300. I also got a 6 month warranty on the axle assembly on top of this.
www.car-part.com I found my axle for $135, less than 20 miles from my house.
You could replace the axle with a non-limited slip unit with the same gear ratio.

 

[Thallarsen]

Wow. I assume you enter "Axle assy rear (w/housing)"
I'm getting prices ranging from $300 for non-graded ones to $650 for "A" axles in my area (Wash DC Metro).
I'm going to search out of state and maybe pick one up in my travels to a more rural area.
If I were to find a comparable rear to my D4, could I assume that a '99 Mountie would work?
Did all Mounties have LSD & 373?

 

[my pos mounty]

Wow. I assume you enter "Axle assy rear (w/housing)"
I'm getting prices ranging from $300 for non-graded ones to $650 for "A" axles in my area (Wash DC Metro).
I'm going to search out of state and maybe pick one up in my travels to a more rural area.
If I were to find a comparable rear to my D4, could I assume that a '99 Mountie would work?
Did all Mounties have LSD & 373?

I think Mountaineers came with a few different ratios. Any rear axle assembly (1997-2001 V8) from an Explorer or Mountaineer will work/fit. (stick with the same D4 though) Theres a couple of Grade A axles in Oilville, VA. (one has only 84K miles) $175. Not too bad, but a little drive.

But lets not jump to that conclusion quite yet. I am not quite convinced it is your bearings, I still think it is a good possibility it is just the LSD clutch packs.

Is there any whine associated with the noise you hear?
What does this noise sound like? High pitched whine? Low vibration?
Is there one particular act that always makes the noise present itself?
Does the truck actually "shimmy" when it occurs, or is it like a vibration?
Does it happen more often when the rear diff oil would be warmer?
Have you EVER changed the rear diff fluid?

You could try changing the rear diff fluid, add friction modifier and pray for the best....might very well be a waste of time/money though.

Try getting the rear up on jackstands, remove the rear drive shaft and turn the pinion shaft by hand. There should be very little (if any) play rotationally and it should feel smooth. In/out or side to side movement would indicate a bad pinion bearing.

 

[Thallarsen]

Thanks for the time that you're taking w/your suggestions. I appreciate it! Your comments/questions are in regular type
Is there any whine associated with the noise you hear? Not much if any at all
What does this noise sound like? High pitched whine? Low vibration? a low vibration, and it's more of a feel than a sound. It's in its early stages, but I'm sensitive to these things, so I'm noticing it early.
Is there one particular act that always makes the noise present itself? Moderate acceleration when starting from a stop; accelerating when going up a hill, healthy accelerating at speed.
Does the truck actually "shimmy" when it occurs, or is it like a vibration? not much of a shimmy at all. Just a vibration reverberating up from the rear end area
Does it happen more often when the rear diff oil would be warmer?absolutely. It's hardly noticeable when cold, but as it warms it becomes a bit more apparent. At first I thought that my new u-joints solved the problem, but after 5 minutes of driving, I got the vibration again.
Have you EVER changed the rear diff fluid?I knew that I was going to be asked this question, and the answer is a resounding no. I doubt that it's ever been changed (since the manual states that it's a 'sealed system that doesn't need maintenance') I've also noticed a small gasket shaped strip of black silicone sealant hanging from the back plate at the pumpkin. It's been that way since I got it 110k ago. Always thought it a bit weird.

You could try changing the rear diff fluid, add friction modifier and pray for the best....might very well be a waste of time/money though. I was thinking about the diff. fluid change myself. Probably a bit late in the game, but it can't hurt $ wise.

Try getting the rear up on jackstands, remove the rear drive shaft and turn the pinion shaft by hand. There should be very little (if any) play rotationally and it should feel smooth. In/out or side to side movement would indicate a bad pinion bearing.I was thinking the same thing. Wish I'd done it when I had the shaft off doing the u-joints, but I was so sure it was the u-joints. 210k and the u-joints were still good? who'dve thunk it?
I might just go the used rear route. Oilville isn't too far from Lake Anna, and I'll be there in early April.
Again, I appreciate your help here. I wish I could return the favor. Does your overhead compass/temp. gauge still work?

 

[my pos mounty]

From what you just wrote, I would bet the farm that it is the limited slip clutch packs.
The replacement packs can be had for under 100 (80 i think). Since you would be that deep into the rear, I would recommend replacing the center pin lock bolt, side/spider gears and a new set of axle seals. Both are not expensive and are easily replaced now, and a real pain in the rear (pun intended) to do at a later date.

Post #4 of this thread has a link posted to a thread on the mustang forum. An excellent write up is post #6 of that thread. However, if you are like me, and need more of a visual, in post #1 of the thread over at the mustang forum has a link to an awsome pictorial article. If you read one and follow along with the pics from the other, you can quickly wrap your head around what you need to do. You do not need to do everything they talk about since you are only removing the carrier, then re-installing it. (Mark everything as to location: caps, bolts, shims, everything MUST go back exactly the same)
Pay close attention to the clutch pack discussion and removal/replacement of the carrier. I am not 100% sure, but I think that if you put the shims back in the spot they were in before dis-assembly, you won't have to redo the clearances, but it might be a good idea to get some gear checking paint to double check the "swipe" on both sides of the ring gear after the re-install.
Someone slap me if I am wrong on this.
Doing this would be easier than replacing the entire rear axle assembly, and if you do get another D4 from a junkyard, theres no gaurantee that the clutch pack is gonna last too long and you might end up doing all this later anyway.

 

[my pos mounty]

For reference purposes check these out:
http://www.explorerforum.com/forums/showthread.php?t=273208
The above link shows what good Vs. bad spiders look like. This particular poster replaced the clutch packs, spider/side gears and the bearings. He had the whine problem, but this is good info to keep in mind. Also shows how he solved replacing the "S" spring.

This next one is authored by the same forum member, working on the same carrier. It will show what needs to be done as far as the gear lash measurement and the paint "swipe" on the drive side and coast side of the ring gear.
http://www.explorerforum.com/forums/showthread.php?t=272694


Theres also a comment by another member about ditching the limited slip in its entirety, not a bad option. Throw in the luchbox locker instead.

 

[blakshukvw]

My truck has been exhibiting the same noises lately. 01 XLT AWD 140xxx miles.
If I were to answer the same questions above for a similar scenario my truck has been exhibiting, I would say:
Not much whine if any.
Same low vibration when going hiway speeds that comes and goes every 1-1/2 seconds.
Shutters upon moderate acceleration or just idleing away from a light or even coming to a stop sometimes,(not sure what to think about that)but does not coincide with downshifting. Almost feels like driving a truck at slow speeds with really nobby tires when it exhibits the slight shutter but it only lasts for a quick second and then it's done.
In my truck it seems to come from the front off the truck and when at speed seems worse when going down even the slightest grades.
Not temperature dependant at all. It has done it when ice cold or when driven for an hour. The low speed shutter is completely random when it will occur but the slight vibration at speed seems to be any time at hiway speeds.

This just recently started in the last couple weeks for me. After reading through the many posts about this same noise and vibration, I'm wondering if mine isn't clutch packs too. My noise and shutter seemed to start not long after I accelerated hard from a stop while turning a little. Any ideas? I'm sensative to new noises in my truck like the OP so it concerns me.

 

[blakshukvw]

Hoping for some insight from "my pos mounty".

 

[my pos mounty]

If your clutch pack is on its way out;
You would only feel the shutter when accelerating from a stop, when turning slow speed and the diff was already warmed up, on occasion you MIGHT feel it a little while after this. I never had it shudder on me when the axle was cold.
Trying to describe the feeling in words over the internet is a challenge, but if you have ever run over the "rumble strips" on the side of the highway, it kind of feels like that, just not as intense. You can't tell the direction it comes from because the whole drivetrain will shudder together.

Have you changed your diff fluid?
Try removing your front driveshaft (aware that it will creep in park) and drive around a few days to see if that is related to this.

 

[blakshukvw]

You described the sensation exactly. Like when driving over rumble strips. Sometimes harsher than others.
Removing the front DS will not harm the transfer case on an AWD X will it?
What does a TC feel like when they shutter?