5th Gen 4Runner transfer case whine after 4.88 regearing

[Cytronus]

I re-geared from factory to Yukon 4.88 in preparation for upgrading to 35s. Since the re-gearing, the transfer case puts out a very noticeable whine/whirl sound which kicks in at about 30 MPH, becoming louder towards 36 MPH and even louder at freeway speeds. The sound is only present when on the gas. When I take my foot off the gas, the sound abruptly disappears. At freeway speeds, I sense a vibration from transfer case. I'm still running 33s so I realize the drive shaft may have slightly higher RPM than before but not that much more.

The rear diff did have a very slight whine at first but slowly faded away to nothing after a week or so. Not nearly as loud as what's coming from the transfer case.

Proper break-in was done and rear diff fluid was changed.

I took it back into Shaffer's Offroad in Union City, CA and they said it's the normal vibration/resonance change that results from re-gearing. I'd like to validate this point of view from you guys with experience re-gearing, if this is true or not. I want to avoid potential damage to the drive shaft and/or t-case. If this is normal, I guess I'll just have to live with it. My gut tells me it's not good.

 

[AMLOR]

This is only anecdotal...I changed mine to 4.88 about 15 months ago and my transfer case is absolutely silent on and off the gas. In addition, there is no vibration from the driveshaft I can detect.
You said you're going to 35's...how much lift and have you adjusted the rear axle pinion upwards to compensate? the pinion /driveshaft angle should be about 1.5-3 degrees from straight...your installer SHOULD have at least asked you about it. Also as we raise our trucks we actually lengthen the driveshaft by pulling the slip joint apart slightly, how much of the slip joint is still left in the driveshaft? too little and it will set up a small but noticeable vibration as that slip joint flexes more than it otherwise might.
On mine when I lifted to 3", I noticed that the slip joint had pulled out just a hair under 2 inches. Once the pinion angle was reset, I got back about 1" on the joint.
Hope this helps!
AMLOR

 

[Jetboy]

I'd say not normal. But it's hard to know from a distance over the Internet. I had no new noises from my regear. The transfer case shouldn't make any new noise. It might have some odd harmonic frequency that travels up the drive shaft?

The diff gears might make noise. Sometimes it's an issue with the gears. Sometimes with the setup. Good gears that are well setup shouldn't make noise. The rear diff is easy to setup. But sometimes they still get screwed up.

You could have a drive shaft put back out of phase. You'd feel it for sure.

Another thought - did you put an arb in the front?

My suggestion would be to start by double checking the gear oil in the transfer case and both differentials just to make sure that your full. Then if you want to see if the noise is coming from the rear end, you could put some heavy weight gear oil and see if the noise goes away. You can also re-lubricate the rear drive shaft and see if that changes anything.

If you put an ARB in the front - I think there's a pretty good chance that's your problem. If you shifted into four wheel drive and the noise goes away, and you have an ARB up front - the noise is coming from the ARB spider gears.

Good luck.

 

[Jeremy556]

Difficult to say from here, but sounds like improper gear setup. How do you know the sound is coming from the transfer case? Do you have chassis ears? They would certainly help pinpoint the source if you have some available.

 

[jp.vegas]

Noise on gas that goes away off gas is strictly diff setup in my experience.

 

[mrblah]

my 4.88 has always had a loud diff whine when accelerating similar to your (sounds like a supercharger whine). Shop says its normal and manufacture says its normal, and my jeep buddies says its normal. Basically, they say its the luck of the draw, i got a loud set As long as diff fluid isn't overheating, it patterns correctly, and your pinion gear is correct not much there to do.

Yeah as others say, its probably diff whine you are hearing.

Anyways, now I run M/T's, and now i have tire howl that hides the gear whine.

 

[2021nightshade4x4]

… did you change BOTH diffs? [emoji23]


Sent from my iPhone using Tapatalk

 

[BlackWorksInc]

It does sound like it's probably your rear diff set-up and/or the combination of new gearing and pinion angle causing some sort of harmonic resonance?

Hard to say without listening to it or at least driving it.

I will say though that we have noisy differential issues with TRD Tacomas with the rear lockers. It's being a thing for years, there's TSBs, but all they exist is to dampen/reduce the noise. The official line is that the way the gears are cut and the gear ratio they use for the locker differentials can result in a noticeable whine/higher pitched growl and that is "considered normal for vehicles of this configuration." One TSB even goes as far as playing with leaf springs and spacers to adjust pinion angle to reduce the noise.

 

[T4R2014]

My bet is on improper gear set-up and resonance through the driveshaft. Shops and manufacturers say it is normal to take liability off themselves. Last thing they want to do is open all that stuff back up to re-do.

 

[Cytronus]

Great input from everyone here. THANK YOU everyone. This why I love this forum. The noise is obviously coming from the drive shaft at the transfer case. The rear is totally silent. I did have an Eaton front E-locker installed at the same time by the same shop but since I'm driving in 2WD, the front E-locker and front diff are not seeing any action and not producing any noise. I did test 4H and 4L with and w/o front locker and that operation is silent up front. The t-case at the point of rear drive shaft connection is precisely where the noise is coming from, whether in 2WD or 4WD. I have a 3" ICON lift and have NOT done any rear axle pinion angle adjustments and wasn't aware I had to, nor have I checked the slip joint. The installer didn't ask about it either. I will see if I can make the adjustments to the pinion angle and if that helps. yes, both front and rear were re-geared. Have to re-gear both.

 

[Cytronus]

transfer case noise

Difficult to say from here, but sounds like improper gear setup. How do you know the sound is coming from the transfer case? Do you have chassis ears? They would certainly help pinpoint the source if you have some available.

it's obviously coming from just below the shifter. When I lean over and place my ear right over the shift lever, it's very apparent. I then got my bro in the car with me and he sat in the cargo/trunk area to listen to the rear diff....nothing, not a sound. Had him jump up front to the passenger seat and listen near the shift lever and he clearly heard the whine from the transfer case location as well.

I'm thinking about mounting a GoPro under there to record it up close in action.

 

[bayaz]

Why would the pinion angle change after the re-gear? Also, what can the shop do to fix the pinion angle misalignment other than replace the driveshaft with a double cardan?

How clean were the diff fluids? Were there any metal shavings caked onto the magnet?

 

[rdruss]

Why would the pinion angle change after the re-gear? Also, what can the shop do to fix the pinion angle misalignment other than replace the driveshaft with a double cardan?

How clean were the diff fluids? Were there any metal shavings caked onto the magnet?

Adjustable rear trailing arms.

 

[Cytronus]

Rear Diff fluid after 600 mile break-in and drain plug before and after

Yukon's gear break-in procedure recommends 5 continuous drives at 55 MPH for 20 miles each with speed consistency and no stops. After each drive, stop and let gears cool completely. I performed 6 of these drives to be sure of proper break-in. After that - about 600 miles after the re-gearing, I drained the rear diff fluid and replaced it with Redline full synthetic 75W90 gear oil (the expensive good stuff).

The shop that did the gear install said they put in fresh non-synthetic gear oil. What came out after 600 miles was a weird olive drab green color. I was a little surprised by this color for the gear oil having supposedly been fresh after the new gears were installed. I got the sense the shop re-used the gear fluid that came out of the diff when they took it apart, knowing it would be drained in 500 miles or so. I had previously changed the gear oil 20K miles ago with Redline synthetic 75W90, which has a clearish bright yellow color.

the drain plug had nothing abnormal on the magnet. A 1 to 1.5mm layer of very fine metal powder was on it. No larger pieces of metal shavings. Nothing even the size of a grain of sand. It was extremely fine. This looked totally normal to me and in line with what I noticed when I changed the gear oil 20K miles ago with factory gears.

 

[Hammer0313]

Some good info in this thread, would like to hear more about pinion angle with lifting our rigs.
I've done 2 re-gears in the past and the first was perfect, no noise or vibrations. Second re-gear left me with a horrible howl/growl that never went away; everything worked well but had to live with it. I've never heard of noise coming from a TC after a re-gear, seems off to me. I'm curious if there is any vibrations coming from the TC?

 

[Jetboy]

I did have an Eaton front E-locker installed at the same time by the same shop but since I'm driving in 2WD, the front E-locker and front diff are not seeing any action and not producing any noise. I did test 4H and 4L with and w/o front locker and that operation is silent up front. The t-case at the point of rear drive shaft connection is precisely where the noise is coming from, whether in 2WD or 4WD.

FWIW - the front diff spins the spider gears in the front diff when in 2wd. So if the spider gears are noisy, the front diff will howl at speed when in 2wd, but when you shift to 4wd the noise goes away. Much like the front needle bearing issue. But, the sound is a lot different. I've had both issues. ARB changed spider gear design in about 2018ish and went from cut gears to forged. So the gear faces are rough forging and make a lot of noise. With mud tires you wouldn't hear it, but on street tires is was pretty noisy. Enough so that I swapped the diff for a 2nd ARB and then ARB replaced with a 3rd one that I just resold NIB and cut my losses. I would go for an Eaton next time, or at least pull the ARB apart and figure out how to polish the gear faces on the spider gears to quiet them down. I like that they made em stronger. Don't like the noise for a daily driver/road trip mobile.

But it doesn't sound like this is the problem for you anyway. If it's still there in 4hi - it's not the front spider gears or the front side bushing/bearing.

One other random thought - I'm sure you've probably already looked, but is it possible they tied up the shaft with wire or something and accidentally left it on? Or maybe they didn't get the gas tank skid bolts back on tight and it's touching the drive shaft or something like that? I'm sure you've already done a visual inspection, but just a thought. Not on the 4R, but I have had my rear shaft bolts work loose on the flange. So maybe double check the drive shaft bolts and see that they're tight.

 

[mrblah]

FWIW - the front diff spins the spider gears in the front diff when in 2wd. So if the spider gears are noisy, the front diff will howl at speed when in 2wd, but when you shift to 4wd the noise goes away. Much like the front needle bearing issue. But, the sound is a lot different. I've had both issues. ARB changed spider gear design in about 2018ish and went from cut gears to forged. So the gear faces are rough forging and make a lot of noise. With mud tires you wouldn't hear it, but on street tires is was pretty noisy. Enough so that I swapped the diff for a 2nd ARB and then ARB replaced with a 3rd one that I just resold NIB and cut my losses. I would go for an Eaton next time, or at least pull the ARB apart and figure out how to polish the gear faces on the spider gears to quiet them down. I like that they made em stronger. Don't like the noise for a daily driver/road trip mobile.

But it doesn't sound like this is the problem for you anyway. If it's still there in 4hi - it's not the front spider gears or the front side bushing/bearing.

One other random thought - I'm sure you've probably already looked, but is it possible they tied up the shaft with wire or something and accidentally left it on? Or maybe they didn't get the gas tank skid bolts back on tight and it's touching the drive shaft or something like that? I'm sure you've already done a visual inspection, but just a thought. Not on the 4R, but I have had my rear shaft bolts work loose on the flange. So maybe double check the drive shaft bolts and see that they're tight.

Lol I think you solved my problem with whine which is probably arb related.

I’ve grown use to the sound doesn’t bother me at all anymore. I figure the day I don’t hear it then something is wrong.

To answer the question someone asked about pinion gear or angle is due to screw ups during install during regearing is why it matters.

 

[BlackWorksInc]

Why would the pinion angle change after the re-gear? Also, what can the shop do to fix the pinion angle misalignment other than replace the driveshaft with a double cardan?

How clean were the diff fluids? Were there any metal shavings caked onto the magnet?

It wouldn't, the reason so many of us are wondering about pinion angle is because he said he added a lift recently/had a lift installed. That would change pinion angle naturally, so possibly the angle with new gears is causing something odd with the noise. Was a thought.

 

[Cytronus]

It wouldn't, the reason so many of us are wondering about pinion angle is because he said he added a lift recently/had a lift installed. That would change pinion angle naturally, so possibly the angle with new gears is causing something odd with the noise. Was a thought.

My lift was installed in 2016 and never caused any noise so I don't think it's the pinion angle since that hasn't changed at all with the re-gear.

 

[mrblah]

My lift was installed in 2016 and never caused any noise so I don't think it's the pinion angle since that hasn't changed at all with the re-gear.

i dont think it is your pinion gear either. i just mentioned it as previous because its one of those things the installer checks.