Hi Guys. Got an interesting one for you. It’s kind of a long read but this is a problem I’ve been living with for years so spare a thought for poor old me hahahahah
I'm on a few other local (Canadian) Forums but this one seems to be the most active one right now so thought I'd try you guys to share my pain and perhaps somebody will say "Oooh, I had that problem - it was.....". Nobody else has a clue.

So first the car itself...
2006 GT. 45,000Km so 28,000 miles.
Loved and cossetted since new (I'm original owner). Up until Covid I used it on various road courses, (NEVER BEEN DOWN A DRAG STRIP) perhaps 4 or 5 track days a year. It's set up for that perfectly within the limitations of being able to drive it to events. Seen rain less than 10 times, stored on a ramp and looks like new underneath. Never been hit or bumped, not an oil drip or spec of rust.
Full Ford Racing Track pack suspension, watts linkage, Gran Turismo brakes, trailing arms, blah blah blah.


About me... Long history of cars and road course racing from shifter carts thru sedans in Europe and I ran Nascar Whelen Short track late models when I got to Canada for a few years. I've run cars and I built them. I don't say that to "be that guy" but only to show you that I kinda "know what I'm doing" with this stuff although I'm always listening and learning LOL

OK so if you drove the car blind folded you'd simply think it's new, it’s that nice. If ever it needed anything, it got it. I've had to have it professionally certified a few times prior to being able to run with some "more enthusiastic and serious" track day groups and every time the mechanic shakes his head at the car. Things I have changed for preventative-maintenance have been brakes, control arms, diff pack, fluids and recently I changed the clutch out for a Mcleod.

So then, what could possibly be wrong in the Garden? For a long while there's been a clunking under the car which was always random and pretty much impossible to replicate on demand. Now I'm talking about for like 5 years! But this was when I was still tracking it and having the safety done on it and the thing always ran like a champ, ZERO handling issues. In fact on track the thing never clunked at all, it was only ever at low speed, perhaps pulling away from a Red light (Not John Force style, I mean Granny style).

It kinda pissed me off that it did it but at the same time there wasn’t anything clearly wrong and it’s not like it ever created a real problem for me. It went and stopped as well as I could ever want, straight and true. It was just a tedious noise…

During Covid I decided to rein back the track day action and part of that process was to make the car more enjoyable to drive on the road. The first thing I did was to pull off the Watts linkage because even though it was the single best thing I did to the car in terms of handling, it employed solid heim joints and mounted straight to the frame so was a bit “twitchy” on the road over train tracks, pot holes, normal cheap road maintenance type stuff. At the same time I was actually fairly confident it was the source of the ‘clunk’.

Well, it made no difference to the clunk. Of course, why would it? I’m really not that lucky.

So since then, which was a couple of years ago, I’ve randomly changed suspension components in a lazy bid to kill the clunk. I’ll try to remember what I’ve done: Full grease and lube – multiple times / Lower control arms / Sway bar drop links front and rear / Trailing arms / Third link / Full nut/bolt release and re-torque multiple times
I’m sure there’s more and of course, nothing I removed was worn out or even remotely tired anyway.

So we come to more recently, this Summer. There’s a particular parking lot I use for work which has a slight uphill entry lane. I don’t use the Mustang as a Daily Driver but this year I took it a few times to work on a nice day. Now, when I turn off the road to go into the parking area and ‘bump up’ the lowered curbing, I go annoyingly slowly and my approach is like 45 degrees. We all do that of course, to minimize the chance of scuffing the front lip etc. I turn LEFT into the lot so my front left touches the little bump first – CLUNK!! Then the right front hits the bump and silence. Next up is the left rear and as soon as that touches the bump – CLUNK! So now I can finally replicate the clunk at least. I had a friend stand by the car to identify where exactly the noise is coming from and all he could say was “Holy F*** that’s loud”.

In the car it’s impossible to say where the noise is coming from. Passengers always say it’s 100% on his side whilst I’m 100% sure it’s on the driver’s side LOL The other day I went up the little ramp (VERY slowly by the way) and it literally felt like somebody had hit the floor with a hammer, I felt the sharp concussion on my seat.

Somebody said, and I agree, that altering the diagonal loading is causing a component to react violently instead of smoothly taking it in its stride – BUT which one!?!?!?! In my experience the louder the noise the easier it is to see where it came from plus there’ll be other indicators in the driving. But I have no witness marks anywhere and the bloody thing still drives like a new car ! Normal and track driving on all types and quality of roads no clunking. Random low speed diagonal loading – clunk.

Somebody MUST have fought this exact thing before.

HELP !!!!!!

 

I'd start by going over all the suspension and drivetrain bolts and tightening everything up. Other than that, check the center bearing on the driveshaft as well as the exhaust system. Something might be loose and hitting.