Hi all, as some of you are aware I just finished overhauling my steering and suspension. I have been working out kinks since the initial test drive. Good news is that shortening the sway bar end links and fabricating lowering blocks for the sway bar chassis mount has eliminated the interference between the sway bar and chassis. Later on I am actually going to add on to the spacers to get more proper end link geometry.

Aside from that, there are now two things left on the list of issues. It seems that one of my lower control arm spherical bearings is faulty, and ORP is sending me a new one (free of course, thanks John). The way I discovered this was during a post-drive inspection I was tightening all hardware and when I torqued on the passenger side strut rod nuts I heard a quiet clicking sound. It took a moment for me to isolate where the sound was coming from, because the movement was so little it wasn't visible anywere. By putting one hand on the lower control arm and lower c.a. mount I was able to determine that the lower control arm was moving in/outboard.

What I am posting about today is this issue: During suspension travel while driving I kept hearing this odd sound, from the drivers seat it sounded like something bumping. When I slid underneath the car and lifted/pushed down on suspension I found that the sound is the inner fenderwell between the shock tower and the radiator support flexing and unflexing. Makes that warble warble sound of flexing sheetmetal.
I have a few questions for ya'll, 1) Anyone ever experience this? 2) What is causing this? 3) Easiest way of making it go away?

The unibody is straight and there is no damage to the cars body anywhere, it was just fully checked at a frame shop. Is the monte carlo bar involved in creating this sound? I was thinking of drilling two holes across the area that's flexing, and on the wheel well side install some aluminum bar to stiffen things up. However this sounds so cheesy I am hoping I don't have to drill holes just for this...

Awaiting suggestions...

 

Hmmmm.. I have a clank.. maybe the same noise on a hard left turn going up my driveway. You may have just figured it out for me.

 

Yea it had me worried because it sounded kinda loud when driving. Shows how much body flex these cars have I guess. In the (far) future I know I will do the boss chassis mod and get some sort of cage in the car. I am still not sure what I want to do, but someone suggested coating the underside in something to make the metal less prone to flexing. I couldn't think of anything that would work.

 

It sounds to me like you've got something in a bind if it's oil-canning that section of your fenderwell. A monte carlo bar won't cause this if everything that is suppose to be is square.

That is an odd spot that shouldn't be under any undue strain running down the road.
Cobbling a brace together would be masking the problem.
Pictures?

 

fastback: I checked all the steering and suspension parts after assembly for any bind, there was zero. Obviously once the sway bar was installed that changed things. There's really nothing to show in pictures, the metal is not bent/crushed or anything like that, it simply shifts from convex to concave causing the warbling/bump sound. I also agree this is a strange spot to experience this, I am unfamiliar with the term oil-canning.
This is what I was thinking of, but it doesn't make sense. Now that I am running stiffer springs and shocks in the front of the car, even with the monte carlo brace installed, perhaps flex is occurring in either the shock towers or the inner fenderwells since they're connected. This seems highly unlikely since this happens when I move suspension by hand with car on the ground. I just can't think of anything that makes any sense... Maybe the 1.5" arm drop is putting pressure on a part of the shock tower thats flexing?
I will tell you what though, I am going to re-tighten the monte carlo hardware and check all fender bolts and radiator support bolts and see if this makes a difference. Also I will check the crossmembers. I don't think it will make a difference but its worth trying. This is a peculiar issue for sure...

 

"Oil-canning" describes your flexing fenderwell..you know, like the bottom of the Tin Mans oil can or the roof of a fastback.


Does the fenderwell flex if you disconnect the sway bar?

 

I will have to check on that... How could the sway bar cause this?

 

Just trying to figure out where the bind is. You mentioned that your sway bar geometry wasn't right so I'm trying to cut the legs off the elephant & whittle the problem down.

When did this flexing issue start? What was the last thing you did before you noticed the problem?

I think I'd start loosening things up one at a time and retesting and try to find at what point the flexing stops.

 

The upper portion of the end link and sway bar come very close to the subframe up front. You may need to shorten your end links. The sway bar end links can be shortened easily and are inexpensive. Are you using polyurethane anywhere up front? Poly does not flex, thus causes other thinks to break loose. Sounds crazy, did you have a couple of spot welds break loose where the apron and radiator support come together? if not, I'd be looking at the end links as your problem.

 

I agree with Groho. You are stiffening your suspension without stiffening the chassis itself is what it sounds like to me. Cars flex at their weakest point when you start to stiffen things up (fatter sway bars, stiffer bushings, more support overall). In this case, you may need to reinforce that part of the frame since older mustangs were never that stiff from the factory.

Start from the bottom though and work your way through it. Fix your suspension geometry. Test for the problem. If it still exists, reinforce the area that is flexing, readjust your suspension if needed after stiffening the area that's flexing.