Piston Slap: Range(r) of Motion, OMGWTF Edition

Sajeev Mehta
by Sajeev Mehta
piston slap range r of motion omgwtf edition

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?

Send your queries to mehta@ttac.com

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  • Gone4Day Gone4Day on Jun 21, 2010

    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.

  • Tiredoldmechanic Tiredoldmechanic on Jun 21, 2010

    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.

  • Arthur Dailey I grew up in an era when a teenager could work pumping gas or bussing tables and be able to purchase a vehicle for a couple of thousand dollars and drive it with 'uninsured' status.If a parent advised on the purchase of the vehicle, they would most often point us to a large, stripped/base version, domestic sedan with the smallest possible engine.These cars generally had terrible driving dynamics and little to no safety features, but were easy to work, had large bench seats/interiors and not enough power to get out of their own way.
  • MaintenanceCosts I'll guess: 3rd owner, never did even basic maintenance, major component failed, car got towed from the apartment complex parking lot, no one bought it at auction because the repair bill exceeded the value.The chrome pillar appliques support this hypothesis.
  • MaintenanceCosts I'm generally in the "I want them to have all the new safety stuff" camp, but new cars are both too fast and too isolating these days. They mask speed enough that a new driver can get way in over his head without really realizing he's even going that fast. This is especially a concern with my youngest, who wants to do everything he does faster. (He has zero fear tearing down hills at 25 mph on his little 20" wheel bike.) I'm hoping for something that is slow and communicates speed well, although I'm not quite sure there is any such thing in today's market.
  • KOKing I test-drove a used Equus Ultimate (the one with all the back seat doodads) that was a trade-in at a Ford dealer, and although it was VERY nice to be in as a Lexus LS with Ultra Luxury, it was supposedly in a minor fender-bender that probably wasn't repaired correctly (like a pinched bus cable or something?), and random features didn't work at all.I think this car suffered the same problem in the US that the VW Phaeton did, and probably would've done better if it was badged a Genesis from the get-go.
  • Analoggrotto Tesla owners are still smarter than anyone else, regardless.