B58 crankhub and timing guide

The B58 kills the crankhub as a separate part. There is no bolt-on hub like the N54/N55/S55 — the vibration damper (with the reluctor for the crank sensor) bolts directly to the crank nose with torque-to-yield bolts, and the chain sprocket drives through its own path. If you came here looking for the N54-style "crankhub slip" job, the honest answer is that the B58 factory data doesn't describe one; what it describes is a damper bolt set that is renewed every time it's touched, and a chain drive that was redesigned for the B58TU. Here are the real numbers.

Damper-to-crank bolts

The damper job, factory shape

1. 01Battery negative off (12V-system warnings throughout), underbody protection out, right front-end strut off — the document notes driving without the strut brace is not permitted, so it goes back on with new screws.
2. 02Counter the crank: position the holder (counter support) and fasten with its screw, slide the counter support toward the flywheel, and turn the engine at the vibration damper until the tool's gearing engages the flywheel ring gear, then tighten the bolt. That locks the crank through the damper you're about to remove.
3. 03Pull the damper bolts, lift the damper off.
4. 04The front radial shaft seal gets replaced whenever the damper is removed — it's an explicit Additional Technical Information note in the procedure, not an option. Install dry: do not touch the sealing lip, do not oil it; the seal goes on with the install tool (sleeve set `11 8 800`), and the damper goes back on with the factory fitting aid (silhouette-foil tool, B48/B58).
5. 05Clean the damper's sealing surface, hand-start the new bolts, torque to 40 Nm + 120°.

Chain tensioner

The B58 timing chain tensioner is a genuinely accessible job — no engine removal:

Front-end strut and intake silencer housing out, tensioner unbolts with conventional tools. Have a cloth ready — a small amount of oil follows it out. If reusing the tensioner, drain the oil chamber on a level surface, slow compression, twice, and catch what comes out.

Timing chains — the engine-out reality

The chain replacement document (11 31 052, "Replacing both timing chains") is an engine-out, assembly-stand job: engine support arm bolted to the stand at 130 Nm (95.9 lb-ft), engine fixture at 105 Nm (77.4 lb-ft), cylinder head, oil sump, and rear timing case all part of the teardown. The torque rows that matter once you're there:

What changed in the B58TU — the factory's own words

The B58TU functional description documents a full chain-drive redesign, and it's the most citable "why" in this whole engine family's timing story:

• The two-piece chain drive became a **one-piece chain drive** — the deflection via the intermediate shaft to the upper timing chain and the second timing chain were eliminated.
• **8 mm sleeve-type chains** are used as timing chains.
• Tooth counts changed with the omitted intermediate ratio: crankshaft sprocket 23 teeth, VANOS adjusters 46 teeth each.
• The oil pump/vacuum pump still runs its own drive chain off the crankshaft, now upstream of the timing chain.

None of that is tuning-forum lore — it's the engine description document, stating what the TU bought and why the two jobs aren't the same job.

VANOS work

The adjuster and central-valve jobs carry their own torque rows:

Special tools worth knowing by name: wrench socket 2450487 for the VANOS adjuster, adapter 2469138 for the VANOS central valve, gauge 2358122 to secure the camshaft at TDC, locating stud 2288380 to lock the crankshaft at TDC, gauge 2420824 to position the high-pressure pump to the crankshaft, and the counter support 0496595 that holds the flywheel for damper-bolt work.

Coverage notes

Coverage verdict, honestly: damper, tensioner, adjusters, and VANOS procedures are complete with full torque tables, and the B58TU description documents the chain-drive redesign. But the chain replacement itself is written as an engine-out assembly-stand job — there is no in-car chain procedure in this data for the B58, and we won't pretend one exists. There are also no failure-mileage statistics in the factory docs; the tensioner's accessibility and the TU redesign are the facts, and anything more specific is someone's guess.

Every number traces to the ISTA ids in the sources; the complete procedures live in ISTA.