CC Literature: 1977 Ford Noise And Vibration Diagnosis – Never Has A Dollar Been So Useful

On a snowy Sunday of late, my dad and I made our annual sojourn to a local Model A Restorers Club swap meet, which was unfortunately less well-attended by vendors this year (most likely due to the aforementioned snow).  I only came home with a couple orange parking light bulbs for the Riviera and this useful book, which was on sale for a whole American dollar.  Take that, inflation!

Click on any photo for a larger version in a new window.

There are few mechanical maladies more frustrating than those that involve NVH, the dreaded “Noise, Vibration, and Harshness.”  I can make almost anything run, but tracking down those shakes and rattles is far more esoteric, especially considering that every old car I’ve ever driven has a vibration of some sort at freeway speed.  Certainly, some will mention that their old car doesn’t shake or leak oil and always nails down 33 miles per gallon with a 440 motorhome engine and 3.91 gears.  You’re lucky.  In my experience, at the 70+ mile per hour expressway speeds I maintain to avoid getting clobbered by a wayward minivan with a trash bag covering the side window, things shimmy a bit.

That’s always been a problem, even when these cars were new.  Ford’s little handbook offers some sage advice on the theory of diagnosing problems, and it’s good common sense stuff for any mechanic.  In essence, use your experience and ask the customer questions.

Aside from the dubious pop culture interpretation of Sherlock Holmes and his attire (sorry for the nerdiness – I’m a longtime fan of Sherlock Holmes stories), Ford offers advice that many of us would be wise to follow, such as “new parts are just that…[it] does not mean they are good functioning parts.”  Advice for code scanning mechanics today: “Don’t cure the symptom and leave the cause.”  (I can hear it now: “It’s gotta be the oxygen sensor.”)

Along with a cutaway image of a Cougar XR-7 and a list of the frequencies of common vibration-causing components in cycles per second, there is a handy glossary of terms.  There are few things more frustrating when working on a car than “floating terminology,” in other words, when a manual uses several words for the same item or expects that the mechanic knows every technical term.

There are plenty of terms in the world of NVH.  (The World of NVH.  That sounds like a great Hanna-Barbera cartoon.)

The process of diagnosis begins on page 9 with the road test.  It suggests taking the customer along to get a better idea of the specific situations where a complaint occurs, along with taking notes so you’ll remember a problem later.

The best note on page 11 reminds the mechanic to not touch anything before performing a road test and a visual inspection.  Many mechanics are guilty of making assumptions based on their backlog of experience and are eager to get the job done.  That’s how one becomes simply a parts changer.  Ford recommends looking in the trunk for “unusual loads,” checking tire pressures, and noticing “bright spots where components may be rubbing against each other.”

Next, the book identifies five types of conditions in the world of NVH and the speeds where they usually occur.  “High Speed Shake” is the problem I most often see, and it is often attributable to tires (and often exacerbated by my home alignments on a sloping garage floor).  I’ve gotten better at that over time.

Ford knew that mechanics often appreciate specific directions (especially if they’re inexperienced).  Chances are, one of the dealer’s mechanics was a specialist at this sort of thing and didn’t need the handbook, but it’s a good guide for those who don’t necessarily work on NVH problems every day.  Tools such as a dial indicator aren’t found in every home garage, but they are available for a reasonable price at outlets such as Harbor Freight (don’t laugh – I’ve had mine for years).  In addition to checking for wheel and brake rotor runout, you can check ring and pinion backlash, crankshaft endplay, and much more.  It’s a gift that keeps on giving.

Here are some more actions for repairing a high-speed shake.  I’d love to have an on-car wheel balancer.

Honestly, if you’re removing the center section of your differential to repair a high-speed shake, you’re having a really bad day.

“Tip-in Moan” is a category that deals with that mooing sound one gets when one steps on the gas.  It can be as innocuous as a loose air cleaner lid or as serious as a broken engine mount.

Driveline vibrations are often caused by universal joints, but NVH is a cruel mistress and will often send you tripping down the wrong path.

Incorrect driveline angles due to worn mounts or bushings can cause vibrations.

So can your pulleys and belts.

As always, the diagnosis often takes longer than the repair, so the latter pages of the book detail how to do the actual work.

Here’s that handy dial indicator again (I even got a mini-wheel attachment for mine so I could check tire runout – I’m fun at parties).

Replacing the driveshaft would probably result from off-roading your new T-Bird.

Ah, the classic “hose clamps around the driveshaft” trick.  I’ve never done it myself, but I’ve heard it works.

Oddly, as a guy for whom a conclusion is a foregone conclusion, the lack of one in Ford’s manual is stark and troubling.  On the other hand, nobody would read it anyway, and I’m glad that someone threw this little booklet in a desk somewhere and forgot about it.

I wasn’t there, and it would be interesting to hear from those who were, but dealer training back in the “old days” seemed fairly thorough, with filmstrips, manuals, and pamphlets available for every make and model.  This concise little manual is actually very helpful for the amateur garage mechanic of today who doesn’t necessarily deal with these things more than a few times in their lives.  Who’d pass that up for a buck?

Postscript: I also have a much more thorough book that discusses the same topic but was published by General Motors in the early 1990s.  It includes some more advanced tools to find vibrations, and it discusses the science behind vibrations in much more detail (perhaps too much unnecessary detail for the average line mechanic).