By on June 21, 2010

TTAC Commentator 67dodgeman writes:

Sajeev, I have a question for the Piston Slap expert. My son drives my old ’99 Ford Ranger (extended cab, 4 cyl, manual, 2WD) with roughly 130,000 miles on the odometer. I had new tires put on 5 months back at the Firestone place. Then last week, the anti-lock brakes started acting up. As in heavily manipulating the pedal even during very light braking. I assumed the sensor was fried and pulled the fuse, after which everything worked normally. There was a slight ticking sound from the drive train, so I replaced U-joints. Still ticking, but no other obvious issues.

Then, Friday, the driver’s side rear tire and axle came loose. Luckily he was making a low speed U-turn and the last 6” of axle was still in the housing by time he stopped. We jacked the truck up, pushed the axle back in, and pushed it home (two blocks – very very lucky it happened there and not on I-45). I pulled the differential cover and immediately found the (bleeping) C-clip loose in the housing. The anti-lock sensor works off of teeth on the ring gear (just now figured that out), so I’m assuming that having about half the teeth ground off is the cause of the brake malfunction. The oil appeared original, had that burnt smell, and was full of grit. I’m now in the process of changing the whole assembly with a salvage yard spare due to the gear damage.

My question is – what caused the C-clip to fail?  I noticed when pulling the driver’s side tire off the axle that the lug nuts were over-torqued. I put my torque wrench on it and had to dial up to 150 ft-lbs before they would break loose. I’ve had issues with Firestone (and others) over-torqueing wheels in the past. But to pull the axle hard enough to damage the C-clip? Maybe if the brake drum wasn’t squared up properly?

Most of the forum discussions about C-clip failures center on jacked up trucks with over-sized tires. This one is stock. For a plain Jane work/commuting truck, that Ranger has been my best vehicle purchase in the past 25 years. Having an axle fail at 130,000 miles has seriously shattered my faith.

Sajeev Answers:

Funny you mentioned the fear of a Ranger axle failure on the highway, a former co-worker had that problem (2002-ish, 2.3L, 5-speed) on I-10 with less then 100k on the odometer, zero modifications, and no history of heavy duty use.  The axle flew out, landed in the grass, and the Ranger slid across the median and screeched to a stop on the other side of the freeway.  Nobody was hurt (thank goodness) but it totaled the truck.  I called Ford after the owner did the same, but we didn’t hear back from Dearborn. Then I moved on to a new job and new co-workers.  Who knows if anything ever happened, but the Detroit 3 are bad about fixing problems once the warranty expires.

Which seems unfair in these situations.  Trucks axles have legendary toughness, even small Rangers with zero suspension/wheel modifications. The Ford savvy among us may debate the durability of the Ranger’s 7.5-inch differential, but I’ve seen drag racing Fox Body freaks run 12-second timeslips (consistently) with no problems. They don’t suck as much as the 8.8” fanbois may suggest.

Since the C-clip is connected to the wheels, an over-torqued wheel can affect it.  Technically. But it’s a steep jump to assume that cranked-down lug nuts can shave off the ABS exciter teeth, burn the fluid and vibrate the C-clip loose.  I’ve never taken apart a differential, because I know better: that’s suited to a professional.  So I shouldn’t comment.

But I will. And cry foul: a manufacturing or assembly error at whatever factory produces these axles.  Best and Brightest, am I wrong?

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25 Comments on “Piston Slap: Range(r) of Motion, OMGWTF Edition...”

  • avatar

    Dang when you get to that many miles on a vehicle how do you gauge what is an unacceptable failure?

    We who drive “modern” vehicles aren’t used to the maintenance regimens of things like differentials. When should fluid be changed ect…

    • 0 avatar

      People drive well over 100k on axles with original fluid all the time. If it was a big deal, the OEM’s would list axle fluid changes in the owners manual. I have yet to come across that, and yes, I’ve looked.

      Sure, there’s a not-so-fine line between acceptable and not once the warranty expires. But this problem stands right on that line.

    • 0 avatar

      I’ve looked too Sajeev. And the absence of info in a modern owners manual is quite frightening. Some of the new one’s don’t even give the schematic for the fuses. Thank god for the internet, even if it’s just getting online to order a shop manual.

    • 0 avatar

      educatordan – My 4Runner’s manual is pretty good. It pretty much tells you how to do all the recommended maintenance interval checks. It isn’t going to tell you how to diagnose a major problem such as this, but it has pretty solid info on how to complete normal maintenance. My MINI and VW, on the other hand, are horrid when it comes to how to do the various checks or fluid replacements. They both basically have a short, vague list of what items should be checked and say “take to your local ____ dealer.”

    • 0 avatar

      And that’s the thing. Obviously some manufacturers are getting better than others but I get the sense (even only comparing manuals from the 80s till now) that the actual usable info in owners manuals is shrinking not increasing.

    • 0 avatar

      My DD beater 98 Mustang has differential fluid change listed at 100k for the 7.5.

    • 0 avatar

      Sajeev, my Chevy Avalanche does list fluid change intervals for the rear diff, but then it has Positraction. I just changed it at 50k miles.

  • avatar

    It’s not a modern flaw, really. Older cars don’t have axle information either. I have owner’s manuals for cars from the 60’s, 70’s, and 80’s car in my library, so I’ll verify that soon.

    • 0 avatar

      All of my 60s, and 70s GM cars required periodic fluid changes with limited slips. I don’t know about the open differentials. Woe to those who didn’t use the whale oil stuff-noise and eventual failure.

  • avatar

    I had that happen to my V6 99 Ranger in January this year. On my way to work at 5am in the morning, out in the boonies, no street lights. Doing about 30 mph making a slight left turn big bang , left axle shaft, wheel and tire overtook me with a spectacular shower of sparks. Managed to stop on three wheels.

    Had it towed back to my house (retrieved the wheel from a farmer’s field).

    Looked inside differential , left circlip lying on bottom of case, total carnage with pinion shaft snapped in half iron fillings everywhere.Plenty of oil in there. Left brake hub bent over where it hit the road. Not sure if the circlip fell out first or the shaft snapped, I suspect the latter.

    Found a replacement low miles 7.5 with brakes etc in a wrecking yard for $350 and a week later with some DIY was up and running.

  • avatar

    Sajeev, something similiar happened to my dad back in the late 80s, in Houston as well. Except this was a Texaco-owned Econoline with a few passengers (heading to Kingwierd, err…Kingwood) and himself as the driver. He noticed the ride was getting bad, looked in the rearview mirror and every lane had backed way off, then he looked in the side mirror and saw the rear wheel was at a cocked-angle. Not right…not sure of the drivetrain in that Econoline, but obviously a problem Ford has had before. Yes, we still buy Fords.

  • avatar

    There is nothing that an owner or mechanic can do outside the differential that would affect the C-clip. Overtorquing the wheel nuts will not affect the C-clips. The C-clip retains the axle axially: the wheel bearing has no axial retention, and the qwheel attachments don’t affect the retention of the axle in the differential.

    Extremely high cornering forces can damage the C-clips, which is why race cars don’t have them. But a stock Ford Ranger? No way.

    This is a failure of either manufacuring (groove not machined peoperly in axle, wrong materials, wrong tolerances on various parts of the diff, and so on.)

    Even hitting a curb won’t hurt the C-clip, because inward forces are taken on the spider gear shaft.

    One of the lessons to take away from this whole adventure is not to ignore funny noises and strange behaviour from the car. It’s trying to tell you something even if you don’t always want to hear it.


  • avatar
    bumpy ii

    I’m thinking the ring gear failure (and the resultant bouncing off the pinion gear) is what eventually knocked the c-clip loose. Of course, the question then becomes why the ring gear failed.

    Also, this is why full-float rear ends are better. If the axle fails, you just unbolt it and throw it in the bed, unhook the driveshaft (so you don’t blow up the transmission) and pull the truck home.

  • avatar

    Sadly, many are naive enough to believe the factory myth that the unicorn testicle sweat based transmission fluid is going to make it for the life of the vehicle.

    (But it is 100% guaranteed to last the life of the transmission.)

    Same thing with differential fluid.

    I love science. Better living through chemistry. If it reciprocates or manages some part of the thermodynamic equation, I’m gonna treat it and/or coat it. Then use the best synth lube available.

    That being said, even the miracle molecule chains in the bestest of Motul and Redline get chopped up doing their duty on the ring and pinion.

    BMW, MBZ, doesn’t matter. Transmissions and differentials are just too hostile an environment to have their lube survive over 100K miles. I know Ford Fleet doesn’t even reco a trans fluid and filter change until 150K. Take your chances…

    Back to the subject at hand. Solid axle vehicles sometimes lose axle shafts. Complete with wheels. Every so often there’s a readily identifiable causality, but it’s just one of those things. Haven’t seen anything to indicate this as a common Ranger issue, but I may have missed something. They have ‘hum’ issues, but different failure modality.

    Every mechanical device is subject to ‘extraordinary’ failure. The frequency of clip failure followed by axle loss is incredibly low – but when it happens, it will be spectacular. Or at least memorable.

    I’ve seen axle loss a couple of times. But, I’ve seen far more Malibus on the side of the highway. Totally engulfed in flames.

  • avatar

    Thanks for the input. I’ve done some more post-mortem, and have a theory. The picture up above is an excellent starting point. There’s a pin that goes through the spider gears that is removed in that picture. With it gone, the axle can be pushed in and the c-clip removed. The pin itself is held in by a set-screw at the head of the pin. It appears that either the pin itself cracked or the set-screw came out on it’s own. This allowed the pin to rotate in place. The pin has a cut-out that allows the axle to move in and out. This allowed enough play for the c-clip to come loose. I’m betting the pin head itself cracked first (poor metallurgy) rather than the screw coming loose. Ford uses loc-tite on everything, so I can’t see the screw coming loose on it’s own.

    It apparently happened far enough back that the loose c-clip rattled around and tore up the anti-lock brake teeth. The clicking sound was the pin sliding back and forth, hitting the ring gear. Only happened at zero load and very low speed. Nothing was holding the axle in (other than friction) and it took a very tight u-turn to pull it loose.

    Interesting to see that’s it’s more common that I thought. Oh, and as the owner of a 1967 vehicle, we used to change the diff fluid once per failure. No owner’s manual needed for that frequency.

  • avatar

    The rear u-joint went bad on my ’02 Ranger. The truck only had <25K miles of very light commuting duty. Luckily, it made some noise and I was able to catch it before it led to a catastrophic failure.

    A bit later the drum brake seized up and burned. Had to replace the drum, shoes and all hardware. I sold the truck with fewer than 30K miles to a handyman. He asked if I had replaced U-joints and rear brakes. I showed him the receipts and inquired why he asked about those specific items. He explained that he used to work on a maintenance crew at a college. They had a fleet of Rangers and these items always broke.

    My Ranger was a good little truck, but you expect a work vehicle to be made of more durable parts.

  • avatar

    I’d use this as an excuse to ditch the 7.5 (especially if its a =n open diff) for an 8.8 “traction lok”

    • 0 avatar

      If you’ll note in the account, it’s a 1999 model, 4 cylinder, driven by my (teenage) son. After his custom bodywork (dents, dings, gouges, scratches in every single body panel), the truck is worth less than the monster stereo he installed. I used to really like that truck until he got ahold of it. So, no, no upgrade desired. I needed something that would bolt right up and be done.

      There’s a whole ‘nother story about giving a teenage his first vehicle. Don’t even get me started there.

  • avatar

    FWIW, the same thing happened to my mom’s Grand Cherokee back around 1980.

  • avatar

    67dodgeman, I think that’s what happened to mine. The locking pin came loose and allowed the pinion shaft to start moving around. It eventually cracked which allowed the c clip to fall out.

    At the time I didn’t think much about it however at a different time of day with more other vehicles about that flying axle could have seriously hurt someone.

    This is a really common problem on these trucks, when I called junk yards they knew what I wanted before I had finished my first sentence.

  • avatar

    Memories of my misspent youth leads me to believe that somewhat prior to the retainer clip dislodging, there may have been a teeny bit of wheelspin, perhaps on pavement, harsh enough to cause a chunk of one of the pinion gears or spider gears to break off, or even the retainer for the spider shaft, thus the “clicking noise” in the drivetrain. Sooner or later the pieces floating around in there caused the “failure”. These things don’t just happen, it usually stress of some type that may be related to the enthusiasm of the driver.

    • 0 avatar

      Old Guy, it’s a stock Ranger with a 4-banger. If my son got any wheel spin out of it, he’s more of a man than I thought. It just ain’t gonna happen. Plus there were no obvious broken gear teeth other than the anti-lock brake “exciters”. Plenty of grit, but nothing to make me suspect that someone was practicing drag race launches.

      I’ve destroyed more than my share of drive-trains, including multiple diffs in the past. Big block Dodges and full RPM launches will do that. It didn’t look like any of my type of damage.

  • avatar

    Guy up the street blew (flew?) his 350-swapped S10’s axle onto my front yard because of this. Curb on the other side of the street stopped him thankfully. As was mentioned this is why race cars don’t use this diff setup.

    On another note, my dad’s/my ’89 4.3 S10 has 150K on it and has gone through two diff fluid changes, both because the axles needed pulled to change their seals. And it was a PITA if you dropped those clips in the gears.

    Fix the truck and keep going!

  • avatar

    Similar thing happened to me, also in Houston. Driving N. on the 610 west loop at about 70 mph in my ’81 RX-7, the left axle and wheel came out. As the car skidded on the backing plate, the wheel and axle passed me in an arc and I hit it. The axle went into the wheel well and I pole-vaulted over it on two wheels. Put an inch sized hole in the top of my right fender.

    Right behind me was a tow truck driver the saw the whole thing. He said he thought I was going to flip the car when I hit the wheel and axle. He put the car on the lift, tossed the wheel & axle in the back and towed me home. Before lowering the car in my driveway, I put jack stands under it. On the RX-7 the axle is held in placed by a pressed bearing sandwiched between the backing plate and axle housing.Took the axle and walked to the nearest auto parts store and had a new bearing pressed on and was back on the road in less then 2 hours.

    Can’t really blame Mazda for the problem though. I suspect the after market turbo charger I put on it had a something to do with it.

  • avatar

    130,000 miles on the original lube, and never had the cover off for inspection? Asking for trouble, especially with a standard transmission. Add in a young driver who may be a little more “exuberant” with resulting shockloads and wheelspin applied to an already worn out dif. and your results are not unexpected.
    If you get a junkyard dif, replace both C-clips, the planet pin and bolt before you install it. Cheap insurance. In my fleet we pull the cover and change lube oil at 160,000 km without fail. We also change the parts noted above. (with Dodges we do this just before warranty expiry at 100,000 Km). I’m very glad to hear this did not happen at speed, although the U-turn you described is more typical of when you can expect this to happen. Intersections at rush hour are a close second. Completely preventable for an hour of your time and about $35.00 in materials.

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