Clunking sounds and nose diagnosis - Learn how to diagnose driveline noises!

I have read many threads here and out on the net in general from people with early model Ford F150's that have this mysterious "clunking" sound when people accelerate or feather into and out of the throttle.  I have read so many of them, that I had to take a few minutes to address some of the silly ideas I have read that people say causes this problem.  What silly ideas you ask?

That's just what old Ford trucks sound like!  

There are so many moving parts in the driveline, they are bound to make some noise!  

It's just the way old Ford Trucks sound!  Its natural!  

I disagree vehemently!  

Noises like this were not designed into your truck!  That is not to say that design flaws or particular types of suspensions systems are more prone to problems, but to figure out what is causing the problem, one needs to really understand suspension and drive line systems and know how to replicate and diagnose the noise.  HOWEVER, chasing down a noise in a chassis system with a lot of moving parts and wear items requires taking a global overview of the vehicle your working with.  Case in point:

85 bullnose is clunking on acceleration and while tipping into and out of the throttle.  a VERY common problem we read about ALL THE TIME!  

It only has 45K and clearly had a snow plow on it at some point.  Why is this important?  That vehicle has been thrown from drive to reverse about a million times and I can almost GUARINTEE, the driver did NOT wait for the truck to come to a complete stop when he/she did it!  How did I know it had a snow plow on it?  At only 45K the steering Colom and gear shifter is sloppy as hell and there are "witness marks" for snow plow brackets on the frame and bumper brackets.  There are also holes drilled in the dash where they mounted the lift controls and a hole in the firewall which the control cable went through (which is also why the floorboards right below the hole are rotted to death because some mental defective did not grommet or seal the cable to the firewall and water has been coming in for years!).

Most people with half a brain know to check the motor mounts and trans mounts first and foremost as these ALWAYS fail over time!  Once those are eliminated, than what?

Many people are pulling their phone out and heading for Google right about now!  

You read that it is likely the rear axle assembly the driveshaft, the transfer case, bla bla bla.....

Ya slide down, grab the pinion, start slopping it side to side and assume....THAT MUST BE IT!  This pinion has about a half inch of slop, so lets just drop a grand rebuilding the 3rd member!  Once you get the 3rd member on the floor, the backlash in the ring and pinion is likely just fine!  The slop is the collective wear of the ring and pinion, axle splines, and side gear assemblies and axle bearings.  Unless you are replacing EVERYTHING except the case of the carrier, it will be nice and tight for about a thousand miles and than....you will have a quarter inch of slop again!  That's just the way the Ford 9" is! You put a new ring and pinion and carrier and bearings, and axles and axle bearings and it is much tighter, It probably needed that stuff, but after dropping a G on the rear axle, the FU&*ING NOISE IS STILL THERE!  

You read that it is the Transfer case chain!  

Sure, these things are known for stretching these things, but just like the axle, these parts are BATHING IN OIL!  Unless that transfer case chain is about to break through the case, it is highly unlikely that this is going to cause this kind of resounding "CLUNK."

You read that it is the drive shaft slip yokes being dry or the rubbers on the mid-bearing are hammered.

Problem is.....not all F trucks have a slip yoke built into the driveshaft or a 2 piece drive shaft!  This is certainly a possibility on a 2 piece driveshaft with a slip yoke, a double cardan u joint, but my Bullnose has a one piece shaft with no slip yoke and it just clunks like hell!  

Than, the most overlooked problem found these old Ford F150's....THESE THINGS



In Particular, THESE THINGS:



As you can see, the bracket that is supposed to keep the leaf springs bundled together has been beaten open partially and now, the springs are going to clunk and thunk every time you apply torque to the rear axle.  If the plastic spacer is still between the leaf's, the sound is more of a "dead clunk" where if the plastic isolator is pounded out of the spring, it is more of a clacking sound.  

Of course, if you put it in gear from a stand still it is going to clunk.  But if you keep your foot on the brake, put it in gear it is going to clunk initially, but when you take it out of gear, keep your foot on the brake, and than, put it back in gear, the rear axle stays "loaded" so.....NO CLUNK most of the time!  

Ok,  Ok,  so how do you fix it?  Ideally...if it has gotten that bad in the first place, buy some new springs!  If your looking to do it on the cheap, you can crush down the bracket and take some of that slop out of it and replace the plastic insulators, but that repair is not going to last.  Besides that, there are several of these between the spring leaf's and on both sides, and they are ALL beat to hell!  It is VERY common to have the rear drivers side go first!  This is why it is a good thing to to have a very trained ear for listening to noises to determine their geography, or have access to a remote chassis ear to home in on what reagan  of the chassis is making the noise.  

Can other problems cause clunking noises?  Sure!  

Can a single noise be a collection of loose or worn things in the chassis or drive line?  Sure!  

Can noise be transmitted from its origin, through other parts to somewhere else?  Sure!  

But isolating a noise like this takes patience and common sense.  Everyone can create or re-create the noise, but there are MANY modes of operation which must be tested first!  What is a mode of operation?

Everyone knows these:

Acceleration
Deceleration

Some people know these:

Acceleration while turning right or left
Braking
Break torque in forward and in reverse
Driving the truck in 2 and 4 wheel drive
Take each drive shaft out and try to replicate.
Putting it in drive and reverse with the brakes on.
Put some poor bastard under the car while you try to accidentally run him/her over!  

Fewer people know these:

Feathering the throttle at different speeds
Throttle tip in from a roll in a low gear
Throttle tip in from a high gear
Engagement of transmission during "Kick down" for those who have a kickdown
Engagement of torque converter lock up clutch (high gear cruise while just putting enough pressure on the brake pedal to turn the brake lights on and off, thus engaging and disengaging the TCC).
Trying to do ANY of this stuff without causing an accident or creating a road race incident with the mental defective behind you who cant understand why your pumping your brakes at 60 mph on the freeway in the left lane!  In other words, DONT BE A DUMBASS while your doing this stuff!  

Moving on........................

You must FEEL with your hands on the wheel, feet on the floor and on each pedal!  

Knowing how to "jostle" a vehicle while looking for noises is a real talent just like trying to hoist a vehicle and replicate the problem, but many times, these things wont help because the vehicle needs to be moving and/or have weight on the drive line with the suspension or drivetrain loaded.  

Ok, so if you made it this far, your either saying "WELL DUAH!"  or you are totally annoyed because I write like I talk, or you are intrigued enough to really LEARN HOW TO BE AN AWESOME TECHNICIAN and diagnose a problem as opposed to listening to people who know less than you do and being a parts changer or an artillery master in loading the parts cannon, read a little further!  If you are the third person, you probably figured out that I teach technicians this stuff all the time for a living!  I have some advice for you in learning how to DIAGNOSE problems like this.  

Looking at forums is useful, but like Identifix, all your doing is looking at other peoples "ranking" of how frequently something happens and how THEY fixed it.  It can save you time, but often is misleading, convolutes the issue, and above all else, your listening to people who know less than you do about YOUR vehicle!  

I wont even mention how aggravating it is to seemingly find a thread where someone posts your EXACT PROBLEM, and it starts off with 3 people all saying they have the SAME problem and than, by the 5th response people are talking about completely different issues on totally different cars or trucks!  Than, the other problem is that sometimes people do such a horrible job of describing what the problem or response is, you have no idea what they are saying...than there is those folks who write SO MUCH that you lose interest because it was not written in a twitter format and most people under the age of 40 cant handle reading anything more than 280 characters!  Of course, most idiots cant sit still long enough to read anything and are just looking for a quick answer and could care less about learning how to properly diagnose anything!  

Instead of trying to find your exact problem seek advice on how to DIAGNOSE YOUR PROBLEM!  

Instead of just looking for "Clunk in rear of 85 F150"  Try "Diagnosing chassis noise issues."  

OK, I will stop now!  Ask questions if you have them!  Haters can cite my spelling or grammar issues if that is what makes you feel good!  You awesome and outstanding people can feel free to add your bits of wisdom and information.  

I was just board and killing some time this morning and thought I would sound off!  My parts just showed up from the store, so I have to go get back to work! L OL!!!!!!

Wow!  I can't get my head around all of that in one go, but have gone through it bit by bit and it does make sense.

However, there are some noises that Ford trucks make when new.  For instance, back in '72 I bought a new F250 and going from Drive to Reverse there was a clunk.  In fact, all the trucks I test drove had the same clunk.  My truck never got worse during the time I had it, and I've heard that same clunk from many Ford trucks since - and all of them had the C6.  I've come to expect it.

I believe that sound is due to slack in the whole of the driveline and is then essentially amplified by the hollow driveshaft.  And the reason I said "C6" is that an auto is quick to go from one direction to another, and the C6 is the auto that was used in all of these trucks I've driven.

But that doesn't take away from anything you said.  You are right, it takes a lot of detective work to figure out what the problems are.  Both noting what conditions bring on the sound as well as a close inspection of the truck.  And you have a bunch of good ideas on how to do that.  

LOL!  Jake, I had a good time reading at your thread!

Personally, I like Big Brother’s sounds.  The road, the wind, the mechanics…. Modern vehicles are so quite that they don’t distinguish from our living rooms.

In my young years, I was piloting Cessna 150.  THAT’S a LOT of noise.  Nothing to see with an old Ford.

For those who dream about riding their old F-Trucks as if they were designed in 2022, I suggest a Crash Helmets kit, with mikes and headphones.  You can quietly discuss with you passenger, and distress about trying to find all those rattles origin.

Awesome idea on the helmet and microphone!  Believe me, it is ALL coming back to me!  

In addition to my 85 4x4, I used to have an 84 250 2WD and a 78 Bronco.  Both the Bronco and the 85 have all the same driveline clunks and thunks as the Bronco.  The 250 had it's own special noise signatures, but not nearly as much as the 4x4's.  I had to laugh though.  The Bronco had a cast iron 904 transfer case which was gear to gear. Very little noise compared to the New Process 208 with its sloppy chain clacking around down there!  It was just kind of interesting that this was the first thing I noticed when I first drove this 85. It works great, so I aint touching it!  On the good side, the Pickup vibrates so much less because of the longer driveshafts and the lack of those pesky double cardan U joints!  

There are a bunch of reasons why these trucks are destined to just make these noises and a person would have to undertake a full time job trying to continually iron out the issues over and over again.  You stamp out one problem, another one just pops it's head up!  I say "problem" but you know what I mean.  

One of my things at the dealership and in my training classes is NVH.  It is amazing what a VMM can do as it applies to NVH and how far Ford has come in helping technicians in finding and eliminating NVH.  There are just so many inherent design issues all together in these trucks, that there really is no reason to fight it......

They make noise!  LOL!!!!  

When I disconnected the drive shaft and started moving the pinion, it moved about a half inch.  As I took each component out of the axle and got the carrier on the floor, .012" of backlash in the pinion.  Pinion gears and axle splines made up the rest.  Now you just watch, I am building out a new center with new axles and bearings throughout, it is going to be tighter than a nats butt, one trip hauling the race car to the dragstrip and it is going to be right back where it was when I started!  LOL!!! That's just how it is!  Sure, I could slap an 8.8 in there and quiet it up some, but that 9" and cockroaches will be the only things left standing after a nuclear blast!  Noisy...but STRONG and RELYABLE!  

It has been a lot of years since I have driven around in one of these older Ford trucks on a regular basis.  I spend so much time teaching new techs how to locate and eliminate NVH and just kind of lost touch with the joy of having a good old school pick up truck.  I suppose it is going to take me a minute or two to reconnect with my roots guys, be patient with me!  In the mean time, I love to teach, I love to share and I LOVE A CHALLANGE! I just hate to see people struggling with 2 things....noises they cannot find a reason for, and BAD INFORMATION on the internet on how to find them!  That is why I love this forum!  There are a lot of heavy discussions and exchanges of ideas!  I have learned a lot!  

One thing I am going to suggest though.....I don't know how large the tires are on your guys trucks, but consider finding someone to do a road force balance on the wheel/tire assemblies.  If I could put my finger on the one single thing that made a HUGE difference in how this old truck goes down the road, that would be right up there!  If you are not familiar with the process, check it out:

https://www.autotrainingcentre.com/blog/road-force-balancing-explained-auto-mechanics/

My BEST tire, when first doing the road force balance was 45 lbs.  They are now all under 15 and the difference was night and day!  It takes a LOT of stress off of the wheel bearings and suspension as well.  These trucks are notoriously good at absorbing these road force vibrations, but believe me, they manifest themselves in ways we rarely notice until we get them under control, but that is a story for another day!  

I hadn't heard of road force balancing.  That's an interesting read.

I'm getting new tires, Falken WildPeak A/T3W's in 285/75R16, on Big Blue on Tuesday.  But unfortunately the little shop that is mounting and balancing them doesn't have that kind of equipment.  On the other hand, the tires that are on the truck are so bad that it is going to seem like I have a new truck when the new tires go on.