BMW S55 Crank Hub Failure

#S55 Crank Hub Failure Symptoms: Drivetrain Malfunction With No Warning

The S55 crank hub gives you nothing before it lets go. A hard pull or a violent downshift, then a Drivetrain Malfunction message and the engine derated to a crawl. No rattle, no oil light, no gradual change. If that just happened, stop driving and get the car towed.

The hub is a friction joint on the crank nose that drives the timing chain. When it slips, the cams move relative to the crank, the DME sees it, and it derates the engine to protect it. That is why a lot of these end up repairable instead of scrapped.

#Is it safe to drive with a slipped crank hub?

No. Tow it. Nothing locates the hub on the crankshaft, so once it has moved it can move again with every load cycle. On an interference engine, a small offset caught early is a hub and a re-time; a large one at high rpm is bent valves. A flatbed is cheaper than a cylinder head.

The oil pump and high-pressure fuel pump are driven off the same stack. If the joint lets go completely instead of indexing once, the rarer and much worse version of this failure, the pump drives go with it, and losing oil pressure kills an engine faster than bent valves do.

#What the crank hub is, and why it slips

The crank nose carries a stack of separate parts clamped together by one central bolt. What everyone calls the crank hub is that whole stack:

• The timing chain sprocket, driving both camshafts.
• The oil pump and high-pressure fuel pump drive sprocket, which BMW calls Crank Sprocket With Grip Disk. The grip disk is a sintered friction washer. It adds bite to the clamp; it locks nothing.
• The hub and damper carrier the crank pulley bolts onto.
• One single-use M18x1.5 central bolt, which supplies all of the clamping force.

There is no key, spline, dowel or pin between any of it and the crankshaft. Friction alone holds position, so one torque spike past the joint's clamp capacity indexes the stack to a new spot, either on the crank nose or between the chain sprocket and the rest of the stack.

1. A single shock load. A hard launch, a violent DCT downshift, a money shift or a detonation event spikes torque past the joint's holding capacity. Failure is immediate.
2. Progressive preload loss. Torsional vibration at up to 7,600 rpm works on the central bolt until preload bleeds off and an ordinary load event is enough. This is what the aftermarket bolt capture was built for.

The N55 uses the same hardware; the S55 adds torque, redline, pump counter-torque and stiff DCT drivelines. Forums also cite its belt-driven mechanical water pump, where the N54 and N55 use an electric one. That adds load to the same stack, but we rank shock loading well ahead of it.

Why the ECU catches it

The crankshaft sensor reads the flywheel end, so the DME's crank reference is independent of the front hub driving the cams. When the sprocket indexes, the cam-to-crank relationship changes and the DME sees it, which is why a spun hub throws correlation faults instead of just running badly.

#Which cars have it: F80, F82, F83 and F87 M2 Competition

Every S55B30T0 has this hub, including Competition Package cars, the M3 CS, M4 CS and M4 GTS. The base F87 M2 is an N55 with the same sprocket, grip disk and bolt but far less torque through them, and reported failures are much rarer.

#Does a stock F8x S55 actually need this?

For a genuinely stock, street-driven S55: no. It is not a maintenance item and we are not going to sell you one. Shops doing this work report stock and lightly tuned cars going long distances on the factory hub, with failures clustering once E85 and aggressive timing arrive. Stock cars still fail, rarely, including ones with full BMW service history.

Failure-rate percentages by tune stage circulate online. We are not reprinting them: every one we chased traced back to a write-up with no methodology or dataset, and the forum polls are self-selected, because an owner who spun a hub is far likelier to vote. That is not a failure rate.

• Stop money-shifting. Over-revs are logged in the DME, and a logged over-rev is an easy reason for a warranty or service-contract claim to be denied.
• Fix detonation early. Knock events are hammer blows through this joint.
• Keep oil intervals short. That protects the VANOS system, so a 130E20 or 130F20 is more likely to mean something mechanical.

#Should you buy a used F80 M3 or F82 M4?

The hub is no reason to walk away from a stock, well-kept car. Ask the seller whether it has ever been tuned, and have a BMW specialist scan it for logged over-revs and signs of a flash. A tune removed before sale still means the engine lived tuned. An aftermarket hub already fitted is a plus only if you can name the brand and see the install invoice.

#How it gets diagnosed properly

Cam/crank correlation codes do not say crank hub. Cheaper faults set the same codes. If yours are intermittent, VANOS solenoid failure is a far cheaper place to start.

The codes reported in S55 hub cases are 130E20, intake camshaft angle deviation to crankshaft outside tolerance, and 130F20, the exhaust-side equivalent. They come off the DME with ISTA or another BMW-capable tool. Confirm them on your own car; do not self-diagnose off a code in an article.

1. 01
   Pull full fault memoryISTA on the DME with freeze-frame data. Hard and repeatable points at mechanical timing; intermittent points at VANOS or a sensor.
2. 02
   Rule out the cheaper causesSludged VANOS solenoids, a stretched chain, worn guides, a bled-down tensioner, a failing cam sensor, and low oil pressure at the VANOS units.
3. 03
   Mechanically verify the timingCrank locked at TDC with BMW tool 11 0 300, then try to fit camshaft tool 11 4 280. If it will not seat, the engine is out of time. Never rotate the engine with the locking pin installed.
4. 04
   Find where it movedChain stretch can also put the cams out. Confirmation means the front timing cover off, burnished faces, factory witness marks out of line, and tensioner and guide wear measured.
5. 05
   Check for valve contact before quotingCompression and ideally leak-down on all six. Even numbers mean it was caught early. A low cylinder means bent valves and a quote that moves by five figures.

Nobody can reliably catch a slip beforehand. One UK shop claims it can spot prior bolt movement on a diagnostic laptop, but we could not establish what that check reads. Treat a pre-failure inspection on a factory hub as unproven, and do not pay for one on a claim alone.

#What the repair involves

The engine does not have to come out, and a lot of people assume it does. Drilled solutions are normally done on an engine brace with the front subframe dropped and the oil pan off. Some shops pull it anyway; ask which you are quoted. Once parts are here, plan on about two working days for a non-drilled hub and three or more for a drilled one.

Drilling a hardened forged crank nose means capturing every chip, and with the pan off you can verify that instead of hoping. Non-drilled spline hubs normally leave the pan in, which is why their labor is lower, unless chain-guide debris turns up. Then the pan comes off, the job moves to the higher figure, and we call you first.

1. 01
   Document, strip and lockTiming recorded. Bumper, coolers, accessory drive, pulley and cam cover off; cams locked with 11 4 280, crank with 11 0 300, chain pre-tensioned with 11 9 340.
2. 02
   Brace and dropEngine brace in, subframe down, pan off. Drilled solutions, or a spline job that turns up debris.
3. 03
   Remove the hub stackCentral bolt out with the hub held from the front on a holding tool, never on the timing pins. Crank nose inspected for fretting and scoring.
4. 04
   Drill, if requiredThrough the supplied guide with carbide bits, every chip captured. Expect to consume bits.
5. 05
   Reassemble and re-timeNew single-use central bolt to the ISTA specification, timing verified, oil primed before first start, alignment once the subframe is back.

Which hub, and what a capture plate does

Spline-lock, pinned and keyed hubs all lock the stack to the crank mechanically; only pinned and keyed hubs drill it. A capture plate just stops the central bolt backing out. Sold alone as the crank hub fix, ask what it does about the friction joint. The answer is nothing. Paired with a spline-lock hub it belongs: Vargas Turbo Technologies, whose SplineLock is the best-known part here, specifies its hubs to run with its bolt capture, and our estimate includes it.

Both styles have been reported failing when machining was poor: cracked material at a keyway relief, runout and seal leaks from an inaccurate spline, a hub softer than the crank it locks to. Ask what the part is made of, how it is finished and how many the maker has sold. The original hub does not go back on; BMW treats these parts as single use once disturbed.

Part numbers

Timing chain sprocket

Genuine BMW 11317502180

Oil pump and HPFP drive sprocket

Genuine BMW 11418091535, Crank Sprocket With Grip Disk

Central collar screw

Genuine BMW 11217614270, M18x1.5x108, single use

Crank pulley bolts

Genuine BMW 11237575488, M8x20, grade 10.9

Central bolt torque

Not published here. The figure circulating online comes from an aftermarket installer, not BMW. Use the ISTA specification for your chassis.

Before ordering

Part numbers supersede. Confirm every one against your VIN.

#What an S55 crank hub fix costs

These are estimates for an independent European specialist, not a dealer and not a quote; call for current pricing. Diagnosis runs 1.5 to 3 hours for the ISTA scan, mechanical timing check and compression test, and it is quoted before we start.

You will also see spline-lock installs advertised at $1,750 to $2,600, and drilled installs well under our figure. From a shop doing them regularly, that is a legitimate option. On a cheap drilled quote, ask whether the subframe and pan come out and how chips are captured. That is where the hours go.

• Drilled versus not drilled. It decides whether the subframe and pan come out, which is most of the labor.
• Valve contact. The five-figure fork, and why compression comes before the quote.
• A scored crank nose. Bad enough and a new hub will not seat, which puts the crankshaft on the table. Other shops report this; nobody knows how often.
• The chain and rod bearings while it is apart. A chain kit adds roughly $500 to $900 in parts and two to four hours; rod bearings roughly $400 to $700 and six to nine hours. Done later, each pays for the same teardown twice.
• Front-end alignment after the subframe goes back.

We are in Melissa, serving McKinney, Prosper, Frisco, Allen and Plano. Every visit includes a free 49-point inspection, a written quote before anything is touched, and a 24-month/24,000-mile warranty. Wherever you go, ask whether they verify timing with the factory locking tools and run compression before quoting.