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Old 02-03-2012, 11:01 AM
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DaveInDenver DaveInDenver is offline
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Default Drivetrain Singing

Trying to diagnose a noise and thought I had it nailed, but it's looking like more of a tough nut to crack.

I get a high pitched squeal, singing, sounds like a high pitched vibration that has a very small speed correlation, but not directly 1:1. IOW, it starts when I go faster than about 15MPH but the pitch doesn't seem to change significantly as I speed up and slow down. But sometimes it's higher than others.

My working assumption was my carrier was worn out, since it was wobbly and the driveshaft u-joint at the rear output of the t-case had some play. I just figured the bearing was toast in the carrier, so it was singing to let me know.

I got a brand new Timken (Toyota wants $300 for that at my 'good' pricing). This I figured was good enough, seemed well made and was still $150. Dropped off the driveshaft with Bill @ Englewood DS. He fixed it up, balanced and painted.

While it was in the shop I was driving around in FWD and the sound went away, so I assumed my diagnosis was about right. Might have been the carrier or a u-joint at least. But I sorta thought it ruled out bearings in the t-case, diff or rear wheels.

Put the rebuilt DS back in and wouldn't you know the sound is back and now louder even.

Stumped.

I suppose the driveshaft might be the issue, but I highly doubt it now. The only variable I can think of is that the carrier bearing is directional. Very unlikely, but shrug. It was installed the same way both times (the bearing bracket has notches that give you a visual clue).

Bill only replaced one u-joint, the CV u-joints and the diff side u-joint were not replaced since he felt they were still OK. He built the DS about 2 years ago, which at that point was re-tubed (went to heavy wall), a new slip yoke put in, all new u-joints and the CV rebuilt. So even the 'old' u-joints aren't exactly ancient. The sound never changed when I pumped grease in any of the u-joint anyway.

What else can cause a driveline to sing?

Thought maybe the rear diff, but it did this with my old 5.29/ARB diff and was still doing it with this stock factory (yup, worn out) 4.10. This diff has quite a bit of play like any 20 year old Hilux diff does. But maybe the pinion bearing is worn or the gear set worn to the point that the contact pattern is causing it. Maybe the t-case? But both only do it with the rear driveshaft installed and are quiet with it off. I could believe that loading would change the forces on both so I don't think they are ruled out necessarily.

Ideas?
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Old 02-03-2012, 11:22 AM
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Geez. Stumper.
Does it do it in 4WD?
I would have guessed diff, but it appears you have ruled that out. I do not believe the carrier bearing is directional. Maybe BVB will weigh in, or Robbie. I really doubt U joints would sing. Vibrate, yes.
Speedo drive? Yours isn't electronic is it? Or maybe tcase output bearing?
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Old 02-03-2012, 11:40 AM
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Does it in both 4WD high and 2WD. It did not do it in 4WD high with the rear driveshaft removed (e.g. front wheel drive).

Speedo is old style mechanical. That is something I considered, but when it went away with rear DS off I ruled it out. It's a very convoluted path to see how the DS affects that without something else being impacted.

I agree, I doubt it's u-joints. I am very doubtful that it has anything to do with the center support carrier in the DS, too.

My guess is that it is almost definitely not the rear wheel bearings.

I was assuming that it was not the t-case output bearing or pinion bearing since it went away with the DS off. However as I let it sink in removing the DS changes a whole lot. The weight alone changes the way the bearings are loaded and naturally the torque is not transmitted through them.

I did change the t-case about a year ago (sold the Marlin 4.7, put back on my old original I was keeping for duals). I changed the diffs last fall and it did it before and after that, so I am fairly sure it's not the pinion bearing.

So I'm leaning towards my t-case output bearing being shot. I'm going to drain the fluid and refill, hopefully this weekend. I have not done that since mid summer.

Having a good u-joint and snug support bearing also changes the angle the DS force is put on the t-case output, which could explain the change and increase in volume.
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Old 02-03-2012, 11:44 AM
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Old 02-03-2012, 12:10 PM
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Sometimes straws are all you got!
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Old 02-03-2012, 01:23 PM
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So it's not there if you just spin the driveshaft with the rear wheels off the ground (because it's not turning fast enough to whine)? If there was a way to detach the DS at one end (either TC or rear diff) and then turn it with enough rotation to generate the noise. Maybe you could hook the free end of the DS to a drill and start turning it.
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Old 02-03-2012, 01:31 PM
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Yeah, I tried what you're suggesting Matt. Had the truck up on jack stands, idling in 5th gear. Not fast enough and I think not being under any real load made it inconclusive. It doesn't really start until 15, 20MPH.

I was NOWHERE near brave enough to actually crawl under with it on stands running and the noise was not obvious. Now that it's more pronounced I might try that again, though.

I can't hear it driving down the alley (thinking the fences would reflect it better) but I don't like zooming down them and the fences also are good at reflecting the poly bushing squeaks, the old sheet metal buzzes, the exhaust leaks anyway. :-/

I can't spin things fast enough by hand to verify anything other than there's nothing binding that I can tell and the rear brakes aren't hung up or badly out of round.
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Old 02-03-2012, 01:38 PM
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Gosh, I was thinking and thinking and finally it came to me. How to fix your problem.

I think this will do it. Careful, though, too much is not just enough.

Quote:
GRAND BLANC TOWNSHIP, Mich. (AP) - Authorities said a 22-year-old Grand Blanc man faces charges after pumping up the volume of his car stereo. Police said on June 10 the man pulled into a party store in the city about 50 miles northwest of Detroit, where an officer was conducting a liquor inspection. The officer said the loud music was still playing when the man exited his car, which had its windows rolled down.

The Flint Journal reported the officer told the man to turn down his stereo, to which he replied: "What?"

After the officer repeated his request, the man told him that his speakers weren't loud and that it was no big deal, then reduced the volume.

The officer said the man turned up the volume even louder after leaving the store. He was arrested and cited for violating the township's noise ordinance.
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Old 02-03-2012, 01:39 PM
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Quote:
Originally Posted by DaveInDenver View Post
Having a good u-joint and snug support bearing also changes the angle the DS force is put on the t-case output, which could explain the change and increase in volume.
Agreed.... I think that the DS being "tighter" probably got rid of some of the damping the system probably had before.

Since you have swapped thirds and the noise wasn't affected, and the new DS only made it worse.. seems like the only real next thing to look at would be the t case... I too do not think the noise is wheel bearings.

How does a change in load (throttle) affect the noise?
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Old 02-03-2012, 01:43 PM
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My right speaker started making noise like it was blown out and so I haven't used the dash stereo in probably 6 months. I mostly ragchew on the commutes anyway. Also I went back to 30 AT tires/4.10 from the 33/5.29, put back on stock exhaust replacing headers and 2.25" turbo muffler. So the incidental cab noise is way, WAY down. Like almost hold a conversation on the highway quiet.





It should not surprise that that was coincidental with me getting annoying and curious about the noise...





Could have been doing this for a decade for all I know.
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