So on Monday I had a Yukon 4.11 R&P put in myrear diff. Went with Yukon because of the reviews I've heard from a lot of you guys. Even bought the Timken Master Install Kit that Yukon recommends. I had 4 Wheel Parts put 'em in,because I figured they probably did this a little more than the average shop. Assoon as I left the shop, I heard the whirrrrstarting at about 30MPH, peaks at 42 or so then goes back down as I go faster.Calledthe boys at 4 wheel parts, they claimed thatthere will be some noise for the first 250 miles or so and the shopmanager assured me he checked them personally and the pattern inthe gear marking compound was spot on. I told himI'd roll on it for 250 miles but wouldbe coming inif it hadn't gone away and to mark it down that I had an imediatecomplaint.

175 miles later and I'm still hearing it, butmaybe it'sa bit softer (maybe I just want it to be). Very skeptical it'll be gone in another 75 miles. I've been babying this thinglike nobody's business trying to break in the gears correctly, but should there be any noise at all? If I go back next Sat,what'sa few things that I should make sure theycheck?

 

Well, it could because they did not install them corectly.

When gears are really tight, like the teeth are a really tight fit to eachother they tend to make a whine. I would give it 500 miles, and if it is still doing it somthing is probably wrong.

Kinda the same thing with my transfer case, 4wd low was hardly ever used and when its in low and I let off the gas, it whines pretty bad.

 

Yukon doesn't "make" the gears, there are really only two or three actual "Manufacturing" facilities in the world that "make" gear sets.

The the major gear companies buy them and repackage them. The last set of Yukon gears I got had "Richmond" stamped on the side for example. So the whole "buy Yukon cause they are the only quiet 9.25 gears" is really a bunch of internet BS....IMHO

Gear whine can be from a bad set up, or a set of gears that has not been broken in, or from choice of gear lube, or choice of diff cover.

What kind of gear oil did they use? I have found that full synthetic will have more gear noise than a traditional oil, especially during break in. Did they use a synthectic?

What kind of diff cover do you have? Shiny chrome diff covers that are not as thick or can resonate sound differently can also cause noise to be more noticable.

Have 4wp put a conventional oil in like 85w - 90 and when they change the oil, have them check backlash again when they have the cover off.

After break in with a conventional oil if the noise is still present and the backlash is acceptable, you could run a thicker oil like 75 -140 weight.

 

I say it's set up wrong. Possibly a bad bearing though
In my experience new gears are usually quiet initially, even if set up wrong. They get noisy from wearing from the improper setup.

I've done lots of diffs and if it was noisy on the first road testI always pulled it back apart and inspected.

You would think the 4wd guys would do a good job but your shop is only as good as your worst tech.

 

from an archived post:
----

Diagnosing Noise, Part 1
January, 1998

Many things can go wrong inside a differential. Although the hints are often
subtle, most impending failures give fair warning in the form of noise.

Several situations can create ring-and-pinion noise. If the gears have been
quiet and begin to howl, they are probably worn or wearing. If the gears howl
during deceleration only, it's possible that the pinion-bearing preload has
loosened. Howling under acceleration at all speeds indicates that something in
the differential -- gears, pinion or carrier bearings -- has worn or no longer
keeps the gear alignment correct. If the gears howl while accelerating over a
certain speed range, but not all speeds, it's likely that the gears are worn
due to lubrication failure or overloading. When a newly installed gear set
howls, suspect the design or setup.

A common problem is worn carrier bearings, as indicated by a low-pitch rumble
above 20 mph. On vehicles with C-clip axles the noise may vary while
negotiating turns. Worn pinion bearings can cause whirring noises at all
speeds, under deceleration and/or acceleration. Pinion bearings tend to whir,
rather than rumble because the pinion is turning several times faster
(depending on gear ratio) that the carrier. Badly worn bearings can also cause
howl if they do not support the gears correctly.

Worn wheel bearings can be difficult to determine. A very bad wheel bearing
typically makes itself heard with great clarity; it's the bearing that is
going bad, but not destroyed that is hard to find. Turning back and forth from
hard right to hard left can identify the culprit; however, I've been fooled by
right-front wheel bearings that make noise when turning right (which heavily
loads the inside-left-front wheel bearing, but also loads the
outside-right-front bearing).

One common situation that may not make any noise: The pinion spins, but the
tires don't rotate. Broken spider gears can render the differential immobile,
and usually make a loud, crunching sound as they make their final departure. A
broken ring gear will allow the differential to propel the vehicle for about
eight feet at a time, then bang or grind as the section with broken teeth
tries to engage the pinion. Depending on ratio, a broken pinion tooth (or
teeth) will clunk about every two or three feet.

A broken axle is easily determined. After it breaks, a C-clip design axle can
be pulled out of the housing without unbolting anything -- or may even find
it's own way out. On many bolt-in-design axles, the wheel will give the broken
axle shaft away by cambering in at an angle.

A high spot on a gear tooth may sound similar to a broken gear, but will only
make noise while accelerating or decelerating, since the spot appears on just
one side of the offending tooth. A high spot on the ring gear will make a
heavy clicking sound about every eight feet; a high spot on the pinion makes
noise every two or three feet and is much more pronounced due to its higher
frequency.

Whether large or small, differential noise is telling you something. Listen
carefully! If in doubt, pull off the cover or remove the third member for a
closer look. Catching a bad part before is ruins others is definitely worth
the effort.

Diagnosing Noise, Part 2
February, 1998

If you've been left hanging with a "mystery" differential noise that still
refuses to make itself clearly understood, then hopefully this month's info
will lend some more insight.

Anyone who has been involved with four-wheel-drive vehicles has probably heard
of or experienced positraction (posi) "chatter". Posi chatter is noise that is
very recognizable and happens when there is too much friction in the clutches.
Some hard-core offroaders set up their posi this way intentionally. The noise
sounds like someone is pounding on the rearend with a huge sledgehammer. It is
most prevalent when backing up in a parking lot (when everyone around can
stare), and gets worse as the differential heats up. It also tends to show up
on freeway off-ramps and when turning while taking off from a stop sign.

Broken spider gears can sound similar to posi chatter, only more consistent,
regardless of oil temperature. Broken spider gears will make a grinding or
banging sound any time the vehicle is making a turn, and, if they are bad
enough, even when going straight.

Driveline vibrations can be caused by several problems. Worn universal
joints or a driveline that is out of balance are often the problem, but
driveline angle can cause a balanced driveline with good U-joints to vibrate.
If the U-joints are bad, they can cause several different noises from
squeaking, to clunking, to grinding, to vibrations. If the driveline is out of
balance, it will vibrate with a steady pitch that increases as the vehicle
speed increases. If the pinion shaft is out of alignment and not parallel to
the transmission yoke, the difference in the angles between the front and back
U-joints can cause the driveline to vibrate. If the vibration is due to
improper angles, it will create a cyclic sound that increases and decreases in
intensity and is not steady. An out-of-alignment problem can also be
identified by the change in the noise when accelerating or decelerating. As
the pinion yoke torques up from acceleration or down from deceleration, the
rear U-joint angle changes and causes the vibration to change.

A worn side-gear bore in the carrier case will usually cause a clicking sound
as the vehicle is coasting down from speeds of about 20 miles per hour to a
stop. If the bore that supports the side gear becomes too worn to hold the
side gear in place the side gear will "roll over" the spider pinion gears and
will make a clicking noise.

If your differential problem is still not clear and you don't want to take the
time to look inside for more data, you can always drive it until it breaks and
the problem will be much clearer, although much more expensive.

Much more similar differential and gear tech articles at:

http://www.ring-pinion.com

There is also an official TSB from Chrysler somewherre in the 1998-2002 periord on diagnosing differential noise in Jeep Grand Cherokees that has much good info

 

Thanks for the info guys! I've gotta drive on it this week, but by Saturday I'll have definitely put the 75 miles on it to find out if it does indeed goaway and I'll just drive over to 4 wheel parts and have 'em check it out. The tech said they did the intial break-in on the lift at idle for 15 miles. That probably didn't put much torque on the gears and I doubt they reved it up to 60mph to check for whine across the entire spectrum. Yukon recommends 500 mile break-in then a fluid change so maybe that'll be the difference.

All the bearings were swapped out with either the Timken kit or the carrier bearings with the Trutrac I had put in in late July, so I hope that's not the case. The diff cover is the factory cover, so no change there.

I had Royal Purple 75w90 put in the rear end, But I'll swap it with another brand and see if that doesn't help. It might be possible that the syn is a little too good at lubricating and the deburring process isn't as quick as it should be with a non syn.

 

I had the same problem with mine when they installed my gear sets. Take it back. It's either setup wrong (I believe wrong backlash does it.) or it's a noisy set. They ended up putting in a new set in mine and the noise was greatly reduced. Now, that could be a better meshing set and/or they got the setup correct the second time. Mine sounded like an airplane taking off inside the cab. Take it back and make them do it right or put in another set.

 

Don't put synthetic in your differential if you're just going to change the fluid in 500 miles. That's a waste of money. Also did they change the gears in the front? You should pop it in 4 and make sure those ones are set up right as well.

Edit- Never mind about the front one. I'm retarded. [:@]

 

Tech that did my Genuine Gears at 4 Wheel Parts in Orlando told me they don't leave the shop if they whine, and if I heard any whine to bring it back in right away, before any damage is done. He said only 2 factors make them whine. A bad set of gears or a bad install, and that nobody should accept a set of gears that whine. What a difference in philosophy from one 4WP store to another.
BTW - 9,000 on mine and never any audible whine.

 

I would definetely take it back and at very least change the fluid and check backlash again.

It is intersing that you said you have a Detroit Truetrac. That is how I learned that different viscosity oils can allow different levels of noise to either be heard or become nondetectable.I had Detroit Truetrac that was making a bit of noise and by changing the fluid to a thicker viscosity the noise went away. I had originally started with 75-90 synthetic, and ultimatley went with a 80-90 conventional.

While Trachtec\had nothing bad to say about synthetic gear oil, it was their suggestion on my Trutrac to change back to a thicker convenional oil which did eliminate the noise I had.

Either way, you shouldn't have to accept something that is clearly wrong.