By on June 2, 2017

Focus RS differential, Image: blogs.youwheel.com

This week, let’s answer two short questions with equally short answers! – SM

William writes:

I have a Ranger-based question for you: my 2010 XLT four-cylinder regular cab’s passenger side seatbelt will not “pull out” at random times when the wife is getting in the car. Is there a relay or something that controls that?

Sajeev answers:

I do love it when a question’s answered by my shop manual library. Per 2011 Ranger manual, you have a Belt Tension Sensor (BTS), which is a pretensioner assembly within the seat-mounted buckle. This interfaces with the seat-belt assembly, presumably getting a signal from the seatbelt to activate in an accident.

Long story short: I can’t tell which triggers which, so either the BTS is flaking out or the tensioner assembly in the B-pillar is giving out bad advice. Good luck with the diagnosis and repair.

John writes:

I saw a vid of the clutch controlled rear “diff” used on the all-wheel-drive Focus RS in which there is no spider gear set, just the slippage of the inner drive clutch to allow turning. I do understand how the use of this setup along with good computer control of the clutches can provide some real gains in handling and safety. My question is one of life span and the reliability of this setup: will it last 100K miles, when does it start to lose accuracy, and at what cost can it be rebuilt? And of course, when will the tuners be able to program this “monster”?

Sajeev answers:

This video perhaps?

This unit’s durability won’t be a concern for most, especially for its first owner. The computer turns down the power when the differential feels the heat, suggesting there’s no problem on public roads with legal driving, or many weekends of drag strip action, monthly autocross dashes, and even the occasional (non-endurance racing) track day.

Just don’t modify it! Or buy a used one with no service history, signs of being recently returned back to stock, indications it’s been driven hard and slid into a hedge, etc.

This is still a mass-market vehicle dressed up to play with the high-power, high-dollar sports and GT platforms. If this hypothetical is a big concern for would-be Focus RS owners, keep the car bone stock with the exception of a differential cooler.  Or use the money for something loony like a boosted Coyote Mustang/LSX Camaro/370Z with appropriate suspension upgrades to keep the power planted(ish), any number of track-ready pre-owned German machines on a purpose-built sporting chassis…or a C6 Z06 and spank ’em all. 

[Image: FocusRS.org]

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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25 Comments on “Piston Slap: Of Ford’s Locking Seatbelts, Differentials...”


  • avatar
    JimZ

    there are two mechanisms in the seat belt. the first is in the “reel” which the belt winds up on in the B-pillar. This is an inertial latch which locks the mechanism and prevents the belt from extending in e.g. a hard stop. if you have trouble pulling out the seat belt, it’s likely this catch is grabbing the take-up reel.

    The pre-tensioner is a pyrotechnic device activated by the restraints control module; in a crash it tightens the belt from the latch end and holds you more firmly in the seat. Pre-tensioners, like airbags, are a one shot deal.

    • 0 avatar
      dukeisduke

      If you pull on it too fast, you could be invoking the inertia reel. Some will also lock when the vehicle reaches a certain roll angle in a turn (using a pendulum weight).

  • avatar
    DeadWeight

    To be quite candid & very concise, Ford’s lack of quality control in their vehicles is nothing short of appalling.

    From horrid fit and finish, to some of the worst transmissions in the industry, shoddy electrical and electronic components, and a schizophrenic lineup of motors, with some being fair yet others being awful, reliability-wise, it’s no wonder that Ford’s warts will turn to he hemorrhagic legions once the F-Series cash train suffers any significant slowdown, which will happen during the next, inevitable structural erosion in the economy (economies cannot be sustained indefinitely by construction of chain hotels, construction of franchised fast-casual restaurants, pop-up stores, the “tourism-experiential-feels” economy, and purchases of tickets to concerts and sporting events forever, and return of the flipper real estate model of vastly overpriced sheetrock and yellow pine, poorly-constructed, glorified chicken coupes, you know).

    Just as in the 90s and 2000s, the massive, out-sized reliance on sales of pickup trucks, and to a lesser but still notable degree, SUVs, for the generation of a massively disproportionate % of profit will come back to bite Ford hard (as it will General Motors and the artist that is FCA, successor suitor of Chrysler/Dodge/Jeep/RAM).

    • 0 avatar
      JimZ

      what part of this has anything to do with the article?

      • 0 avatar
        28-Cars-Later

        Forget it, he’s rolling.

        • 0 avatar
          PrincipalDan

          Did we QUIT when the Germans bombed Pearl Harbor!

          • 0 avatar

            Ha I used to have a friend who would scream that out when ever some one questioned what ever dumb hold my beer thing we were about to do.

            Example
            Ray do you think it’s a good idea to drive across the farmers field there’s no trespassing signs everywhere and I can see a light on in the house on the hill?

            Ray:
            Did we quit when the germans bombed Pearl harbor! no now get it and floor it.

          • 0 avatar
            dukeisduke

            HELL NO!

        • 0 avatar
          Featherston

          Agreed. And having witnessed the the lovely, well-maintained, and solid-as-a-bomb-shelter 1910s home I grew up in get razed to make way for a McMansion, I appreciated “vastly overpriced sheetrock and yellow pine, poorly-constructed, glorified chicken coupes.” Gotta build out to that lot line, dontcha know!

          • 0 avatar
            operagost

            Re: “flipper real estate model of vastly overpriced sheetrock and yellow pine”.

            Flippers don’t build McMansions. They repair and upgrade existing homes. Yes, the framing standard for 70 years has been yellow pine, and wallboard is superior to lathe and plaster. Not sure why a “flipper” is supposed to frame with, I dunno, maple? and use plaster that requires special skill to apply and repair.

          • 0 avatar
            Featherston

            Note that I didn’t quote the phrase about flippers. You’re correct, flipping homes and building McMansions are two separate concepts.

            I was agreeing with the sentiment that much of present-day residential construction in the US is crap, which it is.

            “[A]nd wallboard is superior to lathe and plaster.” By what criteria? Some, I guess. Quicker and less expensive? Sure. Far, far more common today? Absolutely. A viable alternative to lathe and plaster if the proper materials are used and it’s correctly installed? I’ll agree with that too. Unfortunately, contractors often skimp on materials or time and effort.

            Finally, flippers don’t necessarily repair and upgrade existing homes. They buy and sell in an attempt to make a profit, period. Sometimes that entails improving a home; sometimes that entails making it worse.

          • 0 avatar
            golden2husky

            A good plaster job is much better than any drywall. Period.

    • 0 avatar
      Scoutdude

      Yellow Pine is not the standard for framing material, it is the standard in the areas where it is found, ie the South. Out west the standard is Hem-Fir.

      The flipper model is a good thing. Fact is there are lots and lots of tapped out and trashed cash machines that are finally going across the courthouse steps and it is in the best interest of everyone if they are fixed and returned to the ability to be used as a decent home.

      The vast majority of the homes that are crossing the courthouse steps are not in a condition where they could be sold to an average person who needs a conventional loan to complete the purchase. Very few of the banks that take these homes back are willing or set up to return them to being houses that they would lend on.

      Some houses do seem to be cursed having been repo’ed more than once. However the difference in a repo’ed home from today and 10 years ago is dramatic. 10 years ago the foreclosure would be initiated and completed in ~6 months or so. The person probably thought there was a chance they could figure out how to get caught up when they were under $10K in arrears. So they kept the house in reasonable shape. They also understood that if the house was repo’ed that they would still be on the hook for the difference in what the bank got for it and how much they owed.

      Now thanks to HAMP, HARP and other regulations that made it hard for lenders to repo the houses are usually in pretty sad shape. We now see people who have lived in the home w/o paying for it for 3-5 years or more. Guess what those people who decided to see just how long they could ride in the HAMPster wheel usually trash the house. They don’t repair the leaky roof, or the leaky faucet supply line, they don’t clean up the spills on the carpet, maintain the yard ect. Then when they realize they can’t keep the wheel spinning any longer they sell or take the appliances, light fixtures, wood stoves, and even things like toilets, water heaters and furnaces/heat pumps. Granted some times those things are gone because the person never closed the door the last time they walked out or someone did break in to scavenge those metal items.

      And you can be pretty sure they aren’t going to clean out the fridge and they’ll leave all sorts of trash and maybe when they do decided to take their silverware they just take the entire drawer, cabinet door in the way to remove the dishes, just rip it off and be sure to take that with you, just because. Don’t forget to kick a few holes in the wall or doors on the way out too.

      So what is better overall, those houses sitting empty and deteriorating further or someone willing to take the risk to put out a good chunk of cash and/or take on a extremely high interest hard money loan, and turn it back into a livable financable home?

    • 0 avatar
      Kendahl

      Our 2013 5-speed Focus SE hatchback is approaching 60k miles. In that time we have had two failures. Ford warrantied a piece of broken trim. I had to pay for the passenger side window switch that quit. Otherwise, nothing has broken. Yes, Ford screwed up the DSG transmission and there are small details that could have been done better. But it’s quiet, comfortable, a pleasure to drive and absolutely not a money pit.

      • 0 avatar
        A strolling player

        My 2013 5-speed Focus Titanium hatchback was near perfect for nearly 70,000 miles. Only thing to fail was the water pump just before the powertrain warranty ended. Traded it in on a Chevy SS.

        • 0 avatar
          gtemnykh

          For what it’s worth, my wife’s ’12 Camry just rolled up on 70k with no issues to speak of (she popped a tire on a pothole recently, and screwed up a rear wheel bearing/hub clipping a curb before that). But nothing on behalf of the car itself.

  • avatar
    PrincipalDan

    Limited-slips/locking diffs – the subject of many many pages of inquiries to off-road magazines in my teenage days of having subscriptions. Especially in the era before auto 4×4 systems with guys asking all kinds of questions about the affects on dry road handling, when to leave the hubs locked or unlock them, how to tell their wives to treat the system if the vehicle in question had to pull family duty, etc.

    • 0 avatar
      Tele Vision

      I left the hubs locked in my old F-150 during Winter. All the weight was on the front axle ( nearly ) and it sucked getting out to lock them at slippery intersections once I got into town. The honking was infuriating. It likely only cost me 4 MPG – in a 16 MPG truck with farm gears and pizza-cutters.

  • avatar
    cbrworm

    That’s interesting. So there are two sets of multi-plate clutches. It seems like they would be a wear item for sure. When you are turning, I assume it lets the inner one slip just a little tiny bit? So on high power corners, when the back isn’t sliding, these things are cooking? It seems like on a track, canyon or tight mountain road, these would not have much recovery time to cool down. It does look like there are a sufficient number of plates. Do many electronic LSDs work? I was only familiar with open differentials and the ECU applying the brake to the less loaded wheel.

    • 0 avatar
      Scoutdude

      This is not an electronic Limited Slip Differential, as noted there are not spider gears so it is not a differential. This is a pair of computer controlled couplings. Most of the time in normal every day driving those clutches will not be activated so they will slip w/o any real wear. They will only be activated when the engine is being asked to deliver lots of power or that slipping of one of the front wheels is detected.

      Electronic Limited slip differentials on the other hand are actual differentials with various methods used to connect the two output shafts together. Some are multi plate clutches and others are dog clutches.

  • avatar
    redapple

    Lockers are complicated and expensive.
    Stay with the tried and true and simple.
    Posi.
    With side gears and spring clutch packs.
    1/4 the cost of a locker.
    longer life.
    Locker added performance not worth the added $.

    • 0 avatar
      gtemnykh

      “longer life.”

      I’d strongly disagree there. I also don’t see how they’re much more complex than an LSD.

      LSDs are the ones that wear their clutch packs out, can’t say I’ve ever heard the same of a manually actuated locking rear diff, short of a very un-used one getting a frozen actuator.

  • avatar
    AVT

    Isn’t a posi basically a locker, just without manual control since it “always on.” Thus the reason they suck in snow since the back end goes out in turns since the wheels are still spinning at the same rate.

    • 0 avatar
      Scoutdude

      Well there are all sorts of TEDs or Traction Enhancing Differential designs.

      The basic clutch type often referred to as Posi-Traction, but also sold under a ton of different names. It tries to keep the wheels spinning the same speed but has a limit of how much torque it can transmit to a single wheel with traction.

      Then you have lockers which can either be automatic or manual. When they function as a true locker the shafts will be mechanically tied to each other and will always spin at the same speed.

    • 0 avatar
      gtemnykh

      AVT you’re probably thinking of GM’s “G80” auto/spin locker. It does in fact fully lock up the rear axle when a speed differential of 120rpm is detected between the rear wheels. Most “true” LSDs are never fully locked up, there is a limit to the amount of torque that can be transferred.


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