Haynes is probably the only "paper" DIY repair manual source left, and typically they only publish information on older popular vehicles, where the income stream from the OEM manual is little or no interest to the OEM publisher.

(For instance, Subaru knock sensor uses an M8 bolt, but is ultra-sensitive to the distortion created by overtightening. Final torque is a small fraction of what seems appropriate.)

Lagdprice

Maybe the question could be more simply stated as: Where do service manual publishers get their info? In the example, does Ford specifically make public the original torque spec used for each and every part? Does this information have a centralized source?

I am asking about the manufacturer specific torque specs for a given year, make, model, component/part and bolt/stud (not asking about bolt grade and size standard specs).

While proprietary, the information is not that closely protected, especially on vehilces that are no longer produced by the OEM.

If there are doubts about the aftermarket publishers recycling figures, here is a late 70s Datsun factory service manual:

Jan 12, 2015 — The change in noise when the wheel is turned is usually associated with a bad wheel bearing. Over or under-tightening the hub nut is bad for the ...

2024124 — The Timken Company Wheel Bearing. W. Walmart.com. Bearings Timken 08125. $23.90. Bearings Timken 08125. U. US eBay.

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Search by Part No. allows for look-up of any SKF CR Seals Part Number that is part of the current CR Seals Handbook. Just enter the part number and click ...

200528 — There's absolutely nothing wrong with Sealed Power pistons. This is the 6th year on them and 31psi of boost and not a single problem on CAST ...

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Feb 16, 2023 — I had to drill a couple of the bolts out last time I did a rear wheel bearing. 2007 Volvo V50 T5 AWD M66 - Passion Red SOLD - 2006 Volvo S40 T5 ...

This question is somewhat related to data source ownership and legality of republishing said torque specs found in a given service manual. However, legal consequences are NOT the question itself. I'm simply looking for an explanation of the flow of information from the manufacturing line to the service manuals.

I did at a quick look find one significant torque discrepancy (almost a factor of 2). I'd guess that's because Haynes covers a span of near 10 years while the FSM I have is for a specific year. You can see if the specs get changed over the years that's hard for the condensed book to capture. (It could also be a typo of course)

About 99% of automotive fasteners are NOT critically torqued, so any discussion about bolt grade is moot - as you suggested in your question.

A bad bearing will be noisy, could lead to heat damage of other components, and could seize up or cause the wheel to break off the car, leaving the driver ...

The engineering information is addded to the OEM "repair manual" to aid technicians in replacing components. Often there are general torque rules, which apply when no torque is specifically mentioned. Specialized torque values are provided when the general rules don't apply (knock sensor, oil pan, transmission pan, timing cover, water pump, valve cover) and the desired torque is typically much lower than a blind assumption based on the general OEM rules or bolt size.

Re torque specs Haynes took the liberty of rounding ranges to a single number, eg 93-107 ft-lb in the FSM is 100 in the Haynes book.

T = torque K = standard representing 1.33 U = coefficient of friction D = diameter of the fastener P = necessary preload

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the wheel counterclockwise while gently pulling outward. Rear Hub Axle + Bearing Removal - With will be left with an axle that is exposed on both sides. Tap ...

The "original" information is derived from a collaboration between the OEM engineers, and the OE component manufacturers. So an injector hold-down torque is determined by the application, the materials, and the ultiate goal. Maybe that bolt could be a lot tighter, but not without cracking or distortion of the injector flange, crushing a seal, etc.

Aug 12, 2009 — Try not to destroy it too much, it's important that all the seals fit properly or you will get water and mud in there, your wheel bearings will die and seize.

Torque specifications are determined by the fastener being used. After engineers determine the size and strength for the application, whether the fastener is dry or lubricated, they can calculate the torque specification.

Reputable sources (e.g. Haynes, Chilton's, Alldata, etc) are paying a licensing fee to republish OEM information, or at the very least asking permission.

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Jun 4, 2018 — It was just over $400.00 to replace both front bearings. This was at an independent shop. Dealer would likely be at least $50 to 100 more.

The information flows from the OEM design engineers TO the manufacturing line AND the "repair manual" ... "electronic database". In fact, part of the "design" of the new production vehicle would be developing the tooling to tighten injector hold-down bolts to the correct values. I can't speculate on the exact timing of the information flow, but I am certain the information is not "centralized" with the possible exception of OEM manufacturing enginnering oversight.