If you run a 96-02 4Runner/95.5-04 Tacoma with the ARB front air locker, would you please post whether or not you began hearing a noticeble whirring sound (after the install) from your front diff while doing daily driving in 2WD? If so, did you ever determine if the whirring noise was a normal sound from the ARB front locker (unlocked, of course,) while in 2WD at street/highway speeds?

I recently had a reputable area shop install Nitro 4.56's along with an ARB front air locker on my 2000 4Runner V6 manual. (I already have the factory rear diff locker.) I am hearing a new whirring sound from the front diff area, especially loud with my skid plate back in place. The pitch of the whirring goes up and down with the rotation of the wheels. The sound seems to almost disappear when I shift into 4WD, and then returns and actually accelerates briefly just as I shift back to 2WD.

The shop says the whirring noise comes from the complicated ARB front locker mechanism RD 90 for our rigs, part of which turns all the time in 2WD because of the open diff/ADD used in 3rd Gen 4Runners. Does this explanation seem correct in your experience, or could there be a problem with the gear install?

My factory front diff was quiet before. All parts before and after the install (including suspension lift and 1" diff drop) are the same, except for the 4.56's and the ARB front locker.

 

No problems here, even with running a rear arb it didn't make any noises.

 

My new under 2k mile Rear ARB makes that sound (unlocked).
Its getting quieter the more miles I put on it. Did you get a warranty on it?

 

Yes, it's warranted for one year. Did you re-gear when your ARB was installed? If you didn't, that might point to the ARB as the source of the sound, since the ARB was the only change, unless the tech had to reset your Ring and Pinion while installing the ARB, and messed it up. I don't know what all is involved with an ARB install into an existing R&R.

 

I had 4.88's put in with my front ARB, no noticeable noises in the past 12k + miles on my truck.

 

I bought a complete third from marlin with new gears. I also have a one year warranty.

 

Thanks for the input, nc994run. I don't see a skid plate in your list of mods. My skid plate makes a big difference in how loud the whirring is. With the skid removed, I barely hear the whirring. But with my heavy Budbuilt skid in place--close to the front diff but not touching--the whirring is quite loud since I'm sure the skid deflects the sound into the cab. I assume you have a similar skid, so we are comparing apples to apples. Also, do you have the 1" front diff drop?--If not, I wonder if the tilting of my diff from the 1" drop could affect the balance of the ARB mechanism?

 

I won't give my opinion on what it is. I will let you decipher it yourself.

This is a cut and paste off of Randy's Ring and Pinion's website about noises you hear and the typical problem.

"What is this whirring noise?
Whirring noise only while decelerating at any or all speeds is most likely caused by bad pinion bearings or loose pinion bearing preload, and almost never by bad ring and pinion gears.

A howl or whine during acceleration over a small or large speed range is usually caused by worn ring and pinion gears or improper gear set up.

Rumbling or whirring at speeds over about 20 miles per hour can be caused by worn carrier bearings. The noise may change while turning.

Regular clunking every few feet may indicate broken ring or pinion gears.

Banging or clunking only on corners can be caused by broken spider gears, lack of sufficient positraction lubrication, or worn positraction clutches.

Rumble while turning may indicate bad wheel bearings.

A steady vibration that increases with the vehicle’s speed can be caused by worn u-joints or an out of balance driveshaft.

Clunking only when starting to move or getting on and off the gas might be loose yokes, bad u-joints or worn transfer case or transmission parts."

 

RockyMtRunner, did you ever figure out what the problem was? I just put an ARB in my front diff and have yet to mount and connect the compressor.

 

Glen, the problem was solved by removing the 1" front diff drop that came with my suspension kit. This allowed me to get a significant amount of additional gear oil into the tiny clamshell diff, and the whirring noise went away. Slee Offroad maintains I don't need the diff drop since my suspension lift in front is under 3 inches (2.5"). So far--no noise, no boot/cv problems, and the locker really smooths out crawling over some fairly gnarly stuff.

However, when I started working the front diff and the new locker pretty hard, a new problem appeared. The breather tube started burping oil. Easy solution: I added an extension tube of about three feet, terminating in a little bottle, just in case. Not even a hint of oil in the bottle so far. Whatever oil expands up into the tube as the diff heats up, drains back down into the diff as the oil cools. But I have not yet worked the diff all day long in summer temps. We'll see.

 

Gotcha. Good to know. Thanks for posting up!