weird hum under load (1 Viewer)

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offroadvegan

offroadvegan

Joined
Oct 8, 2017
Threads
61
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398
Location
Oneida, TN
hello!

Searched, nothing clear came up.

Recently had the VC removed by a shop. Replaced u joint with OEM. Driveshaft was rebuilt a year ago.

Now I am getting a hum at low speeds (below 50) that resembles the sound of mud tires on highway. But I don't have mud tires.

When accelerator is let off, sound goes away 100%

1993 on 2.5" OME with 35" Duratracs.

Any ideas?

Appreciated as always.
 
I'd say it sounds like a pinion bearing but what you describe is the opposite of what you'd expect with a noisy pinion.
 
offroadvegan said:
hello!

Searched, nothing clear came up.

Recently had the VC removed by a shop. Replaced u joint with OEM. Driveshaft was rebuilt a year ago.

Now I am getting a hum at low speeds (below 50) that resembles the sound of mud tires on highway. But I don't have mud tires.

When accelerator is let off, sound goes away 100%

1993 on 2.5" OME with 35" Duratracs.

Any ideas?

Appreciated as always.
Click to expand...

Grease one joint at a time to I D which, if any, of them is the culprit.
 
What is the VC you had removed?
 
Remove the zerk from rear slip yoke, spray some brake clean or Pb blaster into yoke then take her for a spin.
Replace zerk and regrease.
 
I disagree with that rear yoke suggestion. A humming noise has never been associated with the splined rear yoke to my knowledge. Sticky splines have symptoms but not that, and you can badly damage the drivetrain by overfilling the rear yoke splines with grease. If you're thinking "clean the dust gasket inside" it's far better to unbolt the rear (mark it first) and pull off the rear section to clean and regrease. It's also worth noting that a powerful solvent will break down the lubricant you have in there nearly instantly.

I asked a specific question about the "VC" removed. Need a LOT of information here. VC? Which driveshaft was serviced and why? Miles? other work done? All 3 Diffs full? Where's the sound coming from - front or rear? But my main question remains - what is the VC the original poster had removed. Messing around in the center differential is serious business and I'd like that explained.
 
Viscous Coupler I assume he's talking about.

Have you checked your wheel bearings lately?
 
iptman said:
Viscous Coupler I assume he's talking about.

Have you checked your wheel bearings lately?
Click to expand...

I have not checked the wheel bearings. But wouldn't those be affected while rotating, and not just while under load?
 
IdahoDoug said:
I asked a specific question about the "VC" removed. Need a LOT of information here. VC? Which driveshaft was serviced and why? Miles? other work done? All 3 Diffs full? Where's the sound coming from - front or rear? But my main question remains - what is the VC the original poster had removed. Messing around in the center differential is serious business and I'd like that explained.
Click to expand...

The viscous coupler was deleted from the t case.

Rear shaft was rebuilt due to a spiral gouge cut into it by the PO. 285,xxx on the chassis, all fluids full. Rig does not leak.
 
Got it. So we're on the same page then. Informationally, the device is somewhat different from a classic VC in that it's designed to merely allow slight differences in speed between the F/R driveshafts while maintaining 50/50 torque split. A great solution to allow sharp turns without binding in a full time 4WD vehicle. A true VC is different in that it provides torque splits from near zero on one end (output) up to whatever the fluid CST and device are designed and has no business on a true 4WD machine. The true VC requires wheel speed differences to activate, meaning just when you want equal speeds (stuck in snow, sand, mud) you are trying to get out with one axle spinning the wheels slightly and not helping as much. On the 80, this device has a breakaway much higher than a stuck in low friction would produced, and as further design intelligence, it is bypassed when in low range for a solid connection.

Anyhow, as so few have done this, I'm curious about the removal and if there was a need to replace the item to maintain spacing inside the center diff? As its removal is an unknown to me (and likely others who could provide input) it might be worth some explanation. Why removed? Who did it? What (if anything) gets put in its place? I don't know if it comes to bear on things but my suspicion is that it would indeed cause one diff or the other to push on the coast side of the gears under certain circumstances more firmly than with the device in place. In other words, yes this could do it. I'll have much more input once you fill me in. Thanks.
 
IdahoDoug said:
Got it. So we're on the same page then. Informationally, the device is somewhat different from a classic VC in that it's designed to merely allow slight differences in speed between the F/R driveshafts while maintaining 50/50 torque split. A great solution to allow sharp turns without binding in a full time 4WD vehicle. A true VC is different in that it provides torque splits from near zero on one end (output) up to whatever the fluid CST and device are designed and has no business on a true 4WD machine. The true VC requires wheel speed differences to activate, meaning just when you want equal speeds (stuck in snow, sand, mud) you are trying to get out with one axle spinning the wheels slightly and not helping as much. On the 80, this device has a breakaway much higher than a stuck in low friction would produced, and as further design intelligence, it is bypassed when in low range for a solid connection.

Anyhow, as so few have done this, I'm curious about the removal and if there was a need to replace the item to maintain spacing inside the center diff? As its removal is an unknown to me (and likely others who could provide input) it might be worth some explanation. Why removed? Who did it? What (if anything) gets put in its place? I don't know if it comes to bear on things but my suspicion is that it would indeed cause one diff or the other to push on the coast side of the gears under certain circumstances more firmly than with the device in place. In other words, yes this could do it. I'll have much more input once you fill me in. Thanks.
Click to expand...

Well, my CDL was not engaging. Hadn't worked since I owned the rig. Finally took it to a shop, and they opened the case, finding the culprit. The gears were misaligned, not allowing the locker to engage. While in there, he also removed the VC (partially as I did not want to spend $700 replacing the questionable party anyway). I dont feel like anything has been lost, but my front tires to chirp on pavement at full crank. Oh well. I don't believe anything else was put in as a replacment.
 
Cruiser804 said:
I'd say it sounds like a pinion bearing but what you describe is the opposite of what you'd expect with a noisy pinion.
Click to expand...
I'm going to disagree here.

Typically, a pinion bearing will make noise under load, and go silent under no load because the pressure has been taken off the worn race.

A bearing with pits in the rollers and pits in the race will set up a harmonic that will not necessarily sound like a grinding, but more like aggressive tires.

I suggest you look at the adjustment and play in your pinion (F&R) to determine if there is excessive play. That can translate to noise first, then to pits.

Otherwise, since the T-Case was what was opened, I would lean toward that since that is what was changed. Look at the output shaft bearings on the F/R of the T-Case.
 
Vegan,

Hmmm. I think you may have been sold a bill of goods on that "misaligned gears" thing. I can think of no way the center differential gears could be "misaligned" to prevent the locker from moving that would not involve complete destruction of the unit. So there's that. On the "removal of the VC" I feel exactly the same. Someone gave you a line of BS if they were able to remove it and there was not a horrendous line item cost to having a short, splined custom shaft built just to replace this 6" long item in your center diff/TC. Unless I've missed something in the 80 world and there is a shaft for eliminating this commonly available? Dunno. So there is that as well.

On the front tires chirping, that sounds like something is indeed locked that should not be as I'm assuming that's in high range? If so, you are likely close to finding out what the weird hum is and it's likely because you're locked on pavement as evidenced by the chirping. So you should recontact that shop and see what they really did.

In my experience, issues with the center diff not locking are extremely simple and due to the locker not being engaged for looooong periods of time. The ball switch gets dirt on it and won't confirm the unit is in low range and thus able to lock. The fix is about 10 minutes if you stop for coffee. Pull the switch, clean with brake cleaner, re-oil and reinsert. So, I'm wondering if that was your problem and a shop did something very wrong. More info?

Edit: Just reread your original post and they "partially" removed the VC? Definitely need more information there as I can think of no way someone can do that. it's a cylinder full of goo and dozens of plates designed to allow the ABS to work and you to turn sharply. With that in mind, you either remove it and replace it with a solid shaft, or do something questionable to cause it to be jammed and no longer allow for movement. But you cannot "partly remove" an item that takes full engine torque. So definitely need more info here. In addition - do your dash lights function properly? When you put it in low range does the center diff lock light go on with the ABS light? I'd think if a shop removed the coupling then your ABS system will no longer work properly in high range as the a F/R axles are now locked together and the ABS system will not detect a locked tire well any more. That was one function of the coupling.
 
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Removing the viscous coupler does not require adding a solid shaft. Removal because of failure of the VC is very common and also needs to be done if installing a part-time spool. If you need more information search for threads related to part-time conversion. There is a good thread I believe Onur started several years ago.
 
Well, here is the deal.

The guy runs a very reputable, local 4WD shop. While he has not worked on many 80s (I have yet to even see another Land Cruiser here in over a year) I was impressed with the level of research he did on the project. I trust the guy.

There was a small/medium size gear he had removed from the case, and said that was the VC. It was about 5" diameter, pretty thick and really heavy.

I am embarrassed to say, I really have no idea on these things as I am not a 4WD expert.

So, that gear is no longer in my vehicle. He didn't add anything to take its place. He did a lot of research on VC deletes, and I thought that was good.

To answer an earlier question - my CDL light AND ABS is on in the dash when in 4L. Also, I did replace that ball switch when I was self-diagnosing/chasing the issue. So we can rule that out. He DID show me where the gears in the case were preventing the actuator from seating the gear. His words were "someone has been in the case before, as the 'timing' was off, and the teeth were mashing, not allowing the CDL to engage."

Am I screwed?
 
VC removed. Cool. That's not the issue, it's been scrapped already.

You got a land cruiser with drive line huuummm. You are not the only one.

Tires chip at full crank on pavement. You totally sure the cdl isn't locked?

Divide and conquer.
Not screwed.
 
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Tedward said:
VC removed. Cool. That's not the issue, it's been scrapped already.

You got a land cruiser with drive line huuummm. You are not the only one.

Tires chip at full crank on pavement. You totally sure the cdl isn't locked?

Divide and conquer.
Not screwed.
Click to expand...

Easiest way to determine on the ground? Light is off.
 
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