new exhaust issues - clunk/contact issue

[Gary Northcutt]

Sorry if this has been asked before. I have a 2005 Mustang Gt. All new suspension, Lowered 1.5" All new Borla cat back exhaust, Professionally installed. My question is, every time I hit a bump the exhaust scrubs/clunks the underside of the trunk area. I have taken it back twice now to have it adjusted and it still clunks. all new hangers and bushings were replaced also. would having it lowered be the issue?

 

[stkjock]

are you certain the clunk is the exhaust hitting?

when the car was lowered, did you use adjustable LCA or UCA and was the pinion angle adjusted?

stock driveshaft?

 

[JC SSP]

Hmmm... Car does look pretty low.

I initially thought it was Panhard bar, but now I am thinking its the exhaust hitting the rear brace...

Have them put the car up on a supported rack (alignment rack) where the body is resting fully on the tires. Bounce the rear end of the car (trunk, bumper, etc.) and have someone underneath look to see where its hitting... There should be a rubbing or scrubbing mark somewhere...

Here are some pics of my 05' rear passenger suspension. The exhaust is nowhere near the Panhard bar, but it does come close to the brace. I am only 1" lowered and never bottomed out.

 

[Gary Northcutt]

Honestly I don't believe they are adjustable. I don't believe it's the Panhard bar. It is a stock driveshaft. I'm just going to have to get it on the lift and be there when they look at it.

 

[GlassTop09]

Honestly I don't believe they are adjustable. I don't believe it's the Panhard bar. It is a stock driveshaft. I'm just going to have to get it on the lift and be there when they look at it.

Hmmm... Car does look pretty low.

I initially thought it was Panhard bar, but now I am thinking its the exhaust hitting the rear brace...

Have them put the car up on a supported rack (alignment rack) where the body is resting fully on the tires. Bounce the rear end of the car (trunk, bumper, etc.) and have someone underneath look to see where its hitting... There should be a rubbing or scrubbing mark somewhere...

Here are some pics of my 05' rear passenger suspension. The exhaust is nowhere near the Panhard bar, but it does come close to the brace. I am only 1" lowered and never bottomed out.

View attachment 88253 View attachment 88254

Hi Gary Northcutt,
What JC SSP posted about was not the panhard bar itself.....but the panhard bar BRACE which mounts just above the panhard bar in which the exhaust piping can get very close to it, depending on the design of an aftermarket PHB brace installed to replace the OEM unit.....

Question.....did you have shop replace the OEM FoMoCo panhard bar brace w\ an aftermarket part that was made out of 1" x 2" metal tubing (like BMR....or the PHB brace design JC SSP is showing in the pictures he posted) along w\ installation of an adjustable panhard bar?

I ask this as I have had this EXACT experience happen to me some yrs back right after I initially replaced my rear axle suspension components w\ a full BMR package (both LCA's, adjustable UCA\UCA mount assembly, adjustable PHB & PHB brace). What I discovered was that the exhaust piping clearance was reduced by the oversized design of the BMR PHB brace (had 1\4" clearance when exhaust was cold but when engine was running & heated up exhaust, the exhaust piping will "expand" meaning it would grow & close up the 1\4" clearance gap.....tis why the rear exhaust hangers use a rod slid thru a rubber hanger....allows the exhaust to grow\shrink from heat cycling) & start striking the oversized BMR PHB brace when going over any type of bump causing the clunking noise at rear of car you're describing. I eventually permanently fixed my issue by removing the BMR aftermarket unit & reinstalling an OEM '14 MY FoMoCo S197 PHB brace, which was smaller in dimension w\ a much better stamping design to increase rigidity BUT it also was designed to mount lower in relation to exhaust piping (had 1 1\8" clearance w\ cold exhaust piping) for adequate hot exhaust pipe clearance vs the BMR aftermarket part.

So what JC SSP is posting about has merit because I've been there, went thru it.

You might want to check for this..................

Hope this helps.

 

[Gary Northcutt]

Thanks everyone for the advice. My thought of it being the exhaust was because all my suspension work was done prior to the new exhaust, then after the new exhaust I started hearing the clunk and rubbing. I have taken the car back to the shop, and they have adjusted, but nothing seems to work. I will look at the brackets and where they come in contact with the pipe, this next week.

 

[Laga]

With the new exhaust, check the hangers, one might be misaligned and not touching correctly. The hanger may need to be bent. This is quite common.