www.chirpthird.com: "Hammering" noise after rear suspension upgrade

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Posted by poSSum (Member # 119) on :

I've installed the following parts:
* G2 poly/rod end LCA's and Panhard
* BMR Torque Arm
* BMR Bolt-on LCA Relocate Brackets
* SLP 1LE Tranny mount
on my '99 SS vert. It already had BMR STB and SFC's. and the '01 SLP OE Bilstein Suspension.

The setup works great, totally eliminated the axle hop I was experiencing. However, at autoX, when accellerating hard in a right hand curve I get a "hammering" sound ... like a rubber mallet bouncing quickly ... coming from the rear.

It doesn't seem to affect handling, and I haven't been able to find any signs of contact.

Any ideas of what I should look for?

Posted by 2002Z4CSS (Member # 1393) on :

Possible exhaust system moving around or even the parking brake cables contacting the floor.Have you checked the trans mount for being loose or broken?

[ 19 July 2002: Message edited by: 2002Z4CSS ]

Posted by poSSum (Member # 119) on :

quote:
Originally posted by 2002Z4CSS:
Possible exhaust system moving around or even the parking brake cables contacting the floor.Have you checked the trans mount for bieng loose or broken?

Thanks! I'll check those items. I replaced the tranny mount with a 1LE mount but I'll check it again anyway.

Posted by OBSSD (Member # 1258) on :

Jounce bumpers maybe? I think I remember hearing about that happening in the road race/autocross forum on LS1.com.

Posted by poSSum (Member # 119) on :

ttt

one more try.

Posted by SS3756 (Member # 601) on :

Check the torque on the LCA's. I had a banging noise as well, but went away when I torqued the LCA right.

Posted by DaddySS (Member # 848) on :

I'm voting for tranny mount issue. I was trying to think of why on RH and not LH turns, and what would cause a rapid hammering as opposed to a random banging. The best guess is the the rapid banging has to do with drive shaft - torque flex from acceleration in turns etc. - so that's where I'd look.

Posted by MaryandRalph (Member # 244) on :

Hey poSSum, did you ever find out what was causing this?

Posted by poSSum (Member # 119) on :

quote:
Originally posted by MaryandRalph:
Hey poSSum, did you ever find out what was causing this?

No ... still collecting ideas so that when I make the time to lift the car and get under there I can check a number of things. And even then, I won't know until after the next autoX as I'm not prepared to make the type of maneuvers required to trigger the noise on the street.

Posted by Xsta Z 28 (Member # 740) on :

Art,

I replied over at LS1Tech, in regards to the pinion angle set the right way. I had mine rotated the wrong way and the rear passenger spring would rub the panhard mount.

But I also thought of these:

Are the LCA's tight?
Is the exhaust pipe hitting the panhard? (Mine did)
Is the exhaust pipe hitting the heat sheild? (Mine does)
Are the shocks tight?
Are the spring silencers installed? (Rubber donuts)

I know some are very elementary, and that you probably have checked, hope these help. Good Luck!

Posted by poSSum (Member # 119) on :

I hope I found it .... the Torque Arm was bottoming on the driver's side of the tunnel ... I ground some material off of it to see if that fixes it and set a note off the Brett to see if he has any ideas.

Does everyone with BMR Torque Arms have two sets of mounting holes on them?

Posted by Xsta Z 28 (Member # 740) on :

quote:
Originally posted by poSSum:

Does everyone with BMR Torque Arms have two sets of mounting holes on them?

Where it mounts to the rear axle??? NOPE

Posted by Xsta Z 28 (Member # 740) on :

Art, my torque arm looks just like this one, it is even silver!

[ 25 July 2002, 04:59 PM: Message edited by: Xsta Z 28 ]

Posted by poSSum (Member # 119) on :

**Update**

The bit of grinding I did on the torque arm didn't solve anything [Frown]

BMR's response so far hasn't been all that encouraging either.

quote:
We have had a few guys encounter this before. On cars that have a lower ride height the tunnel must be "massaged" to create proper clearance, or as you stated, the bracket can be ground on( we prefer the first method as it does not affect the car) to create more clearance.

I'm not prepared to accept that the OE Bilstein suspension qualifies as a "lowered ride height" nor would I consider it acceptable that a part doesn't work through the normal suspension travel range ... especially if it's not highlighted in the sales or installation documentation.

Posted by Xsta Z 28 (Member # 740) on :

Art,

You have mail. Hopefully it won't get kicked back, there are quite a few files of pictures.

Bad news: My BMR Torque Arm has been hitting the tunnel of my Convertible, and that is with just regular driving! [Frown]

My Torque Arm mounts exactly as shown on BMR's site:

Hope the info helps, let me know if you need more!

Andy

[ 03. August 2002, 10:13 AM: Message edited by: Xsta Z 28 ]

Posted by Hawkeye (Member # 88) on :

Checked mine yesterday for Art, mine has some minor rubbing as well. The arm itself has some paing worn off from hitting on the side of the tunnel, and the bracket has been hitting the floor of the tunnel.

I have Bilstein OE, never auto crossed, just street driving and the occaisional 1/4 mile launch. [Frown]

Art advised that Brett said to beat on the tunnel with a mallet and piece of wood, not sure about that, I think I may grind the bracket first.

Posted by poSSum (Member # 119) on :

Thanks Andy and Brian.

I've added to my collection of hammers and will work on clearancing the tunnel Monday. I got some great instructions from Tim so it shouldn't be any problem.

quote:
Just so you know...A true hot rodder would "clearance" the tunnel with a hammer (brick, rock, crowbar, chunk of 4x4, you know whatever it takes)...a true hot rodder would clearance 7or 8 locations (this would occur for a number of reasons...firstly, the first blow would be fairly focused however it would be done while lying on your back in very cramped quarters while bashing your knuckles into the driveshaft and torque arm simultaneausly and with dirt and rust shale falling into your eyes thereby requiring the balance of the blows to be done with eyes shut (your no dumby afterall) or because it was done without looking at the actual location of the "clearance" issue thereby requiring multiple "clearance" areas before finding the actual point of contact OK you are a dumby)). Then...40 years from now, a lucky restorer will trip on your car and decide to restore it. He/she will not believe the amount of butchery (I mean clearancing with surgical precision) that was done to the car. (I know this because I'm rodstoring an ex-racecar).

Posted by OLD GUY (Member # 221) on :

Nah, just get cha some FogHat.

OG

Posted by poSSum (Member # 119) on :

Now I know that the holes are drilled the same as everyone elses and I can use the arm if I go to a Ford 9" (not likely).

I relieved the tunnel a little and also moved the rear end about an 1/8" to the right. AutoX next Tuesday ... we'll see if it helped.

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