Transfer Case Strange Whirring Noise/Gear Whine (1 Viewer)

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My 1996 has been making a strange whirring noise at speeds above 20mph. Gets more noticeable at 45mph, then I don't really hear it after 55mph.

I've asked my passengers if they notice something but nobody else really notices it.
Sounds sort of like gear whine. It's there when I'm on the gas or off the gas, but not when the drivetrain is "floating".

I tried to get a sound clip with my iPhone but it doesn't seem to pick it up.

Some background on my truck:
-VC has been deleted. It was locked up when I bought the truck.
-U-joints have been replaced. They had a tiny amount of play
-wheel bearings have been repacked. Front spindle bushings were replaced by me as PO replaced one of them and the shop that did it screwed it up.
-birfields have also been repacked with synthetic moly grease
-U-joints are greased with wheel bearing grease, slip joints with synthetic moly
-factory locked

I changed the transfer case fluid when I removed the Viscous Coupling, then I did it again about 200 miles after just to make sure that any contaminants that might have been introduced into the case when I opened it up were now flushed out.

F&R diff fluids are also fresh and synthetic.

Otherwise it drives absolutely perfectly. No vibrations, shimmys, shakes, or loud sounds. Just normal road and wind noise on the highway.
Another strange symptom is that I feel like the sound gets worse with the CDL locked. This is both on dirt roads and straight, level, tar roads.

Any advice is welcomed.
Thank you and stay safe everyone.
 
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Good questions.

Noise was present with the VC. In fact when I removed the VC, it got probably 95% quieter.
I used 75W-90.
Maybe I should try 75W-140?
 
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I've done some more reading and I've heard that 75w-140 quiets down the center diff in a lot of cases. I used to do something similar with my Land Rovers (they all had a lot of gear whine). Would use 80w-150 instead of 80w-90.

So I think I'll try putting 75W-140 in it and see how it performs and sounds.

Any objections/risks? Bad idea or is a 140 weight not gonna have any negative affects?
The rear diff on my 2004 Sequoia uses 75w-140 so I think I have some leftover.
 
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Certainly interested to hear how this goes. I'm getting an amazing amount of gear "whine" myself. I recently changed the fluid on the front, center, and rear diffs and swear that the noise dropped significantly for about a week...
 

80t0ylc

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Had it for 3 months now. Was completely stock. I put an OME Stock Height suspension kit on it which lifted it about an inch. Bilstein 5100 shocks.
Just curious, since it hasn't been mentioned yet, you've only owned it 3 months and you might have overlooked it. Are you running matched tires - basically - have you verified all 4 are the same size and approx wear?
 
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I reported same whine issue under same conditions that prompted this thread to LC expert mechanic at local Toyota dealer and as typical gremlin issue, he didn't hear it when he drove it. It doesn't happen all the time, but when I hear it whine my sense is that it is coming from transfer case / center diff area. I readily admit I am not a DIY mechanic and am on low end of bell curve in terms of knowledge. I too, will continue to monitor this thread to see what the final diagnosis and fix is. And, what does VC mean?
 
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80t0ylc

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.............. And, what does VC mean?
Viscosity Coupler - it's a limited slip device. It will allow the drive shafts to turn at different speeds as needed for normal driving on high traction surfaces. On slick surfaces, with uneven traction it will transfer torque to the higher speed drive shaft (the one that's slipping the most) to help. Problem is, with the VC in the 80 series, it has a tendency to fail or lock up permanently when running mismatched tires or not locking the CDL when running on slick surfaces continously. The designers curiously omitted the CDL switch at the same time they stuck the VC into the '93 transfer case - which was the 1st year it appeared. '91 & '92 did not have it, but they had the CDL switch. The VC heats up when it slips excessively and will eventually fail from the heat. When it fails, it has to be replaced - there is no repair of it. It can also be removed and eliminated if desired on the 80 series. If you remove it, you'll need to put a CDL switch in to lock your center diff in high range. The wiring is already there, all you need is the switch. A lot of us have proactively installed the CDL switch and the pin 7 mod before the VC fails.
 
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Just curious, since it hasn't been mentioned yet, you've only owned it 3 months and you might have overlooked it. Are you running matched tires - basically - have you verified all 4 are the same size and approx wear?

Tires are all the same, stock size Michelin LTX M/S. Wear is identical on all four. My only concern is that they are a little old as they have a 2015 manufacturing date. But they were all installed at the same time, They still seem quiet though. Planning on replacing them with 285/75/R16 KO2s once my 4x4Labs bumper comes so I can put the bigger spare on the back.

@PappyVan20 VC is the viscous coupling-- all USDM 80s from 1993-1997 had it. Very common for them to seize up for whatever reason and also common practice to just remove them as the 1991-1992 had the same transfer case without the VC and I believe some 100s had the same. (Look up HF2A vs HF2AV

I'm pretty sure that the gear whine is within the realm of normal for a full time 4WD truck. I don't hear it at all on the highway, just a little when getting up to speed or decelerating. In my Land Rovers, the gear whine was the worst on the highway and everyone could hear it--car guy/girl or not. So in my opinion, my LC is far ahead.

I should also mention that with everything serviced, like birfields, spindle bushings, wheel bearings, drive shafts, etc, the overall noise generated by the drivetrain went down. So I think a big part of the gear whine or drivetrain noise in probably most cases are due to a lack of lubrication or a need of an adjustment in something like wheel bearings. By no means did the original owner abuse this 80, but it is a 24 year old vehicle that needs more maintenance and fine tuning than just fluid changes.

I've ordered a gallon of 75W-140 from amazon and should get it next week. I'm am guessing that it would make a difference, especially once the TC gets warm and the fluid is at the 140 viscosity. Getting warmer here in the bay so heavier oil should help everything out (I think).

Will keep you all posted for sure.
 
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The VC heats up when it slips excessively and will eventually fail from the heat.
My guess is on mine I think maybe someone put it on a 2WD dyno for emissions testing. And that should do it I think.
Original owner said the drivetrain would lock up intermittently at first until it was just fully bounded up all the time. The sound was also really loud and bad.
 
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I have relatively new KO2s all same tread wear. I will bring this thread to the attention of the LC expert. He's supposed to be really good and pretty well known by Cruiser Heads in the area (I got referred to him by a LC nut). My concern is less about the occasional noise, but whether I need to be investing in proactive maintenance. More than one LC expert has said I have one of the "cleanest" and best running stock LC's they've seen in a long time, so I don't want to screw that up. I purchased it for $7k a few years back and have put about $10 or so into it (no mods) to get it to current state.

I have small leak in transfer case at junction where speedometer cable attaches to transfer case. I am having used one shipped (was suggested over just new o ring for some reason). See picture.

I have another question (and again sorry for newbie dumb questions): The image showing the small button...not sure what the heck it does....it does not click or engage....from what prior owner told me...first owner wanted to do more serious offroad and did something to differentials, but then sold it. I've asked mechanics what the heck it is and whether anything was modified. No one has been able to answer me. Wonder whether that first owner could have done something that is causing issue. But, this is not based on any good data, so my thought could be total rubbish.
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80t0ylc

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My guess is on mine I think maybe someone put it on a 2WD dyno for emissions testing. And that should do it I think.
Original owner said the drivetrain would lock up intermittently at first until it was just fully bounded up all the time. The sound was also really loud and bad.
That's aggravating! Sounds like a valid path to your VC's demise. The main benefit I can see to having a working VC is for convenience when traversing slick winter highways. At highway speeds it doesn't get used that much, but adds stability. The full-time benefit is nice enough, but having the VC just seems to give it that extra "edge" over other vehicles I've driven on the rural roads around where I live. But if and when it dies - it comes out and won't be a big issue.
 
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That's aggravating! Sounds like a valid path to your VC's demise. The main benefit I can see to having a working VC is for convenience when traversing slick winter highways. At highway speeds it doesn't get used that much, but adds stability. The full-time benefit is nice enough, but having the VC just seems to give it that extra "edge" over other vehicles I've driven on the rural roads around where I live. But if and when it dies - it comes out and won't be a big issue.

Yeah I would've rather had a working one, but, I probably will never need to use it. I've had a lot of AWD trucks and this was the only one with a VC, so I'm not gonna lose sleep over not having it. But if I ever find a used one for a good price, I might put it back in...
 

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