Help! Rear Diff Whine: Critical? | Ford Explorer Forums - Serious Explorations

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Help! Rear Diff Whine: Critical?


Well-Known Member
January 22, 2008
Reaction score
City, State
Cleveland-ish, OH
Year, Model & Trim Level
2002 XLT SOHC 4L V6

Just finished a long (1200 miles, 2 days) drive from Cleveland to the Colorado Mountains in my '02 XLT (105K miles).

A week before setting out, I started hearing the dreaded rear-end whine when cruising or accellerating at highway speeds (started at about 50 and worst at maybe 65 or so). Figured, no biggie, just a whine. I'll deal with it later... Found and read the TSB (05-12-6), etc., etc. To be safe, changed out rear diff fluid (Mobil1 75/140 syn + FoMoCo XL-3 Fric modifier). Didn't suspect wheel bearings as the noise quits when foot off the accelerator (right?).

However, whine is much more noticeable now, esp. when rear diff is good and hot (like after 8 hours on the freeway at 70mph) When I pulled into town last night, accellerating to 30 mph, and then cruising at 30, sounded like I was driving a frigging' school bus. LOUD whine/howl from the back. Worse than before. Checked rear diff -- no leaks, fluid level good. Still -- foot off the gas and whine goes away. Not wheel bearings/hubs, right?

As an added bonus, while unloading the car to start "vacation," noticed that the left (driver) rear wheel was HOT. I mean much hotter than the other 3. I could put my hand on it, but it was way hotter than what I would consider normal. Maybe bearings AND rear diff?

So now I'm here in a small-ish mountain town. My Explorer is in a local shop to see if driver rear wheel bearing is shot, brake dragging, ebrake not released, etc. Worried about blowing out a tire if things get too hot. :(

Long drive home looming in front of me. Have some time in Denver where I could conceivably deal with the rear diff (don't want to have the local small mountain town shop deal with that).


(1) Should I have the diff fixed here in Denver or is the whine just a whine? I could deal with the noise on my way back to Ohio if I know I'm not gonna' blow up on the freeway in Iowa or Nebraska.

(2) Is the TSB repair something that any tranny shop can do, or is there something gained by shelling out the big bucks for a dealership visit?

(3) Would it be better to try and find a used rear diff? Maybe from an '05 or something, instead of doing the re-build kit?

So frustrated, and nervous now about the long drive home to OH.

Any thoughts welcome. Has anyone just let the whine go for awhile before addressing it? How long did you go and did it get way worse?

Crap. :( Any help appreciated. The noise is so loud and crappy sounding that I'm thinking about it the whole time I'm driving.

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I've let the rear diff whine on my 98 whine for 15,000 miles but I KNEW it was the pinion bearing. Yours sounds like a pinion bearing and possibly a hub bearing as well. I would let a GOOD trans shop look at it. Also put it this way..if you order a new rear center section from me your looking at about $795.00. If you need a bearing kit it's about 85 bucks WITHOUT axle bearings/seals. With them it's like 150.00. So figure 200 for labor your still ahead of the game if you just buy the parts. If your having trouble getting parts out there (I doubt you are) give me a call and we'll get you squared away. Good luck..keep me updated..

Thanks for the quick reply.

Hoping to have the hub bearing issue (or brake, or ebrake) or whatever is making the driver rear wheel overheat dealt with today by the local garage. Then at least I can get the car back.

Regarding the diff -- from everything I've read here (and I've read A TON of stuff about this), I feel like the TSB (TSB 05-12-6: is applicable. Involves a new ring and pinion gear, all new bearings, etc.

I may also need new clutch packs in the rear diff, as it seems mine are shot.

I'd been planning to deal with all of this in good time, but now I'm feeling anxious as things are sounding worse and I'm miles and miles from home.

From what I've read on this forum, dealer fees to deal with the R&P gear rebuild kit are upwards of $1,200. Labor hours for the TSB kit install are estimated at 6.6 hours, so that's at least $800 if you figure in tax. Plus parts (how much is the kit?) Add in the clutch packs and who knows. Clutch pack repairs (by themselves) have their own TSB and estimate 4.6 hours if done alone. I assume there would be some cost savings if both TSB's were done at the same time... ...but who knows!? That's why I was considering a used rear assembly instead.

I just put $600 into new tires before the trip. If I end up doing wheel bearings and then a rear diff rebuild, I'm getting pretty close to the blue book value... Good times. :mad:

Anyone recommend a "good" trans shop in the Denver area?

If you have them do the gears and the clutch packs at the same time it should be cheaper. If they don't then I'd tell them to stuff it and go somewhere else. To get the gears out they have to take the carrier out which is where the clutch packs are. Rebuilding the carrier with new clutch packs takes about 20 minutes once the carrier is out and a Ford Racing clutch pack kit from Jegs is $70 ($120 if they are the carbon fiber clutches like a Cobra.) So it shouldn't be much worse from the dealer. If the dealer wanted to charge you more than 150-200 over the cost of the gear/bearing install, I'd tell them to stuff it.

Just got a call from the local shop. They say that the driver rear hub is "fine" and not causing the rim to heat up as I noticed yesterday. Also, no drag from ebrake or the brake caliber (i.e., the caliper isn't jammed).

So now I'm baffled on that one, too. :(

As for the rear diff, does anyone know how much Ford's "kit" that includes the R&P gear and all the diff bearings costs? Sounds like I can expect to spend about $70 - $100 on the diff clutches...

Again, anyone know a "good" trans shop in Denver?

If I were in your situation, I would look for like an Aamco or other nationwide chain shop that offers a nationwide warranty. That way if you get it done there and come back to Ohio and it starts whining again in a month, they will have to fix it.

Well, got the truck back. Went for a 30 mile ride at freeway speeds.

Good news: driver rear wheel not hot. Go figure. No idea what happened yesterday. It'll probably happen again when least desireable.

Bad news: overall diff hum/whine still there and as noticeable as ever.

As for Aamco -- can I expect them to be cheaper than a dealership?

Found some onlines sources for R&P Gearsets and for Rebuild kits (bearings, pinion seals, etc.)

Ford 8.8" rebuild kit:

R&P Gearset (Ford 8.8", 3.73 ratio):

That's about $300 in parts, plus I'd need a new 8.8" diff cover gasket, diff fluid, friction modifier. Plus I haven't found the clutch packs yet, but figure another $100 or so...

I'm sure the costs shown here are less than dealer costs. I found one dealer price of about $450 for the OEM R&P Kit (5L3Z-4209-C) that includes the gears (I've heard $450 for the R&P gears, bearings, & seals, + extra for fluids, shims, slave pins, etc. -- so figure $550, + clutch packs.

What to do... ...scrounge the parts & find an installer (I can't do this), bite the bullet and go to a dealer, or use a national transmission chain like Aamco.

Advice welcome! Let me know what you think...

I'll destroy those prices if you send me a PM. It's hit or miss w/ Aamco but they won't let you bring your own parts. 6.6 hrs of labor for a rebuild? My guy does it in 1 hr..

The rear diff whine can go forever. Annoying, but not that often severly damaging. Mine has been whining since essentially new 7+ years and 101K miles ago. SOme have grenaded, but it is not that common.

If it whines and you can live with it, I say drive it. If it grenades, it needed repalcing anyway. BTW, mine made several coast-to-coast trips with the infamous whine, no problems.

Good Luck.

Id stay away from AAMCO, much more trouble than it is worth.

enjoying your vacation? if i was in your position i would be flipping.

rear end- happened to my 04 but i caught it right away and got it done under extended warrenty.

another guy in a post said he tried some mobil one fluid and the noise aint that bad.

good luck non the less and keep us updated!

Id stay away from AAMCO, much more trouble than it is worth.

Not always true. We sell some very very good aamcos. Some..not so much. :) You've just gotta get the right one..

Not always true. We sell some very very good aamcos. Some..not so much. :) You've just gotta get the right one..

Yeah, I've heard good and bad, depends on the store and the employees. I do know they warranty their work nationwide though so if your on vacation or something it's our cheapest best bet besides the dealer. Good luck.

The Saga Continues...

Updating this thread with new info and asking more exciting questions! :rolleyes: A thrill ride since I last posted here. Hoping the board members can chime in with some advice.

Sunday afternoon, driving from Winter Park to Denver. Since I had experienced a "mystery" hot brake issue that the local shop couldn't seem to diagnose, I was very careful about not riding the brakes down the mountain. Kept the trans in lower gear and let the engine keep my speed down and keep off the brakes alltogether. Initially no problems.

Hit bumper-to-bumper traffic coming down the mountain and spent maybe 30 minutes of continuous start/stop braking, but never hit speeds above 25 mph.

When traffic cleared up (suddenly), accelerated to freeway speeds and car felt sluggish. Almost put the pedal to the floor to keep at 65 mph on FLAT stretch of freeway. Shifting = fine. Engine = smooth. Even the rear diff whine wasn't too noticeable. The whole car just felt bogged down. Climbed a big hill -- still feeling real sluggish. Start smelling hot brakes. Remember -- I'm going UPhill, not even using brakes.

Get off at next exit: rear drivers brake SMOKING from pads and rotor is scorching hot -- kind of purple-ish. Rear passenger wheel is also real hot, but not smoking. More hot than usual, though. Front brakes and wheels are stone cold.

So -- I'm thinking caliper seized or ebrake shoes dragging, but on both sides? Wierd...

Got a tow to a brake shop in Denver. This morning the go through everything on both sides. Check hubs, calipers, caliper slides, ebrakes, ebrake shoes, discs, rotors you name it. They ran the car up and down the freeway for about 40 mins, on and off the brakes. Can't find ANYTHING wrong. They're baffled. :( Only positive: they didn't charge me a dime! :thumbsup: (Brakes Plus, 10600 West Colfax, "Mark")

So I call the local dealership, 'cause I don't want to have the brakes seize up on me while driving back home to Ohio later in the week. Tell 'em the whole story. They're confused. Service advisor thinks maybe it's a proportioning valve malfunctioning -- basically once the rear brakes are pumped up to pressure, the valve that's supposed to release the brake fluid back into the master cylinder jams and the rear brakes stay "on." I understand the brake system is "split" into 2 zones (front & back), so if this WERE the cause it would make sense that both back brakes were getting hot while the front brakes were nice and cool...

Now here's the thing -- I don't think this car HAS a proportioning valve. I know there's a hydraulic control unit that's part of the ABS system, so maybe that's what he's talking about? ($$$$)

So right now the car's at Ford dealer being "diagnosed."

Any ideas here?!

I've spent 2 entire days of my 4 day "vacation" in CO messing around with this. :mad: Awesome. If it's the hydraulic control unit (dealer quoted part cost = $380) I'm gonna blow a gasket! Even worse if it's the electronic control unit ($480 for the part).

Oh yeah, and the rear differential is still howling like a bloodhound. :mad:

The dealer swears up and down that the differential whine and the rear brake issue I'm having are completely unrelated.

"So I've got that going for me... ...which is nice." -Bill Murray, "Caddyshack"

I posted in your other thread and just caught this one. We have the same problem;) Rear ends whining and my passenger rear smoked badly about 2 months ago. I changed the rear pads maybe a month before it happened. Seemed to come and go. Haven't had any problems for maybe a short while now? (figured the caliper had seized on me but fixed itself) I'll keep an eye on this thread and see how things turn out for ya. Good luck!

Any updates

I would change the brake hoses to those calipers in the rear,
they are relatively inexpensive, and labor is minimal. I've seen a lot of calipers lock up or fail to release because of deteriorated hoses. They tend to be very intermittent too.

Any update on the whine? I've got a 99 EB and we are planning to head to Sol Vista to do some skiing this winter.
I would sure like to cure the whine.


Hey Jay...
I know your issue (differential whine and hit brakes) has been several years back now but did you resolve it and what the heck was it? I have similar issues with mine. Any updates???

stay away from Omera ford in thornton they are crooks and not the very best dealership to get anything done at. One thing though if your back are heating up and the front are staying cool could it possibly be an air bubble in your front brakes? wishing ya the best here in the mile high city. Sorry don't know of any "good" trans places nearby.