Rear End-Thump, Bang, Etc... fixed

[frank700]

Hi guys, I picked up an 03 10th annv. a few weeks ago. Awesome car but had a very loud thumping banging noise coming from the rear end. It happened when you engage the clutch and power was transferred to the rear end. It was loud and you could feel it through the floor.

I searched and went through all the posts on this message board about the problem. Didn't seem like there was a sure fix. I jacked the rear of the car up. I removed the stock exhaust system yesterday to install a Magnaflow. I noticed all the backlash in the driveline. Not sure how many degrees it is on the driveshaft but seems to be excessive. I moved the square metal weight around that hangs below the front of the pumpkin. It moved rather easily. It also moved the whole pumpkin. I looked at the rubber bushing that are on the front of the pumpkin and noticed it was easy to create space between the rubber and the metal that is sandwitched on the front of the pumpkin. I am speaking about the two bolts that go straight up and hold the front of the pumpkin and the square weight hanger. I attempted to tighten these two bolts. They were as tight as they could be. So I needed something to shim theses bushings that are to soft and worn out.

I went to the hardware store and purchased two 3/4 inch washers. $2.60. I took a grinder and cut a slit out of the washer so I would be able to hammer it in between were the rubber meets the aluminum on the housing. I rotated the pumpkin forward to create the space needed to begin to insert the washer. I hammered one washer in on each side. They fit well. Finished exhaust.

Test time.
Started car put it in first gear. Nothing. I went forward and reverse. Nothing. Went out for a 15 mile drive. Not a sound. So long story short because of the rubber mounting bushing on the front of the differential being wore out and probably to soft is causing to much play, slack causing the noise. I know it may be hard to understand without pictures. Sorry. But this is no doubt causing some of the noise related problems in these cars. Hope this is of some help.

Take care

 

[hinds04]

awesome you were able to fix it on your own. I not sure which ones your talking about but maybe look into replacing with bushings made for it. Where are you located in IL

 

[vetteeatinsnake]

Well the heat exchanger just got bumped down to #2 on my list, that noise drives me crazy! Nice job man!

 

[Jimmysidecarr]

Pinion bushings.(the two eyelets on the front of the diff housing and Aluminum bushings closest to the pinion flange pictured below)

These are the ones that without a doubt, get the hottest and by now just about every IRS Cobra out there has probably got worn out, looser than ever bushings.

OP's solution is obviously the low buck version, and hopefully his pinion angle is OK.

Not only do they clunk but they also contribute to wheel hop.

Here is the solution I used.:-D http://fulltiltboogieracing.com/

 

[frank700]

I will try to explain the exact location. If you are underneath your car. Move the square solid weight that hangs just below the differential front to back. That weight is hanging from a metal hanger. Follow that hanger up to where it is mounted. Those are the rubber bushings I'm talking about. Lots of play there. Not good. Need to eliminate that. I inserted a metal washer to make up for the increased tolerances. $2.60 and problem is gone. And I didn't have to drop the differential. If I knew this was going to work ahead of time I would have taken pics. It's pretty easy to do. Easier to do if mufflers aren't in the way.
Push the metal weight towards the back of the car. You will see the space created in the bushings. Insert washer with the staight cut in it between the bushing that is just below the aluminum of the differential. The cut is so as you hit it into place it will allow it to seat without taking the bolt out. Take a ballpeen and hammer hit it in. I am not worried about the washer falling out. It has alot of surface area and the rubber bushing is pushing it up into the aluminum of the differential. I will check on it. But if they were to fall out the worst that could happen is the noise comes back. Pinion angle change is minimal. I didn't loosen the bolt. Just made up for the excessive play.

I'm still amazed that's all it took for what seemed to be a bigger more involved problem.

Frank

 

[GoatSlayer]

Pinion bushings.(the two eyelets on the front of the diff housing and Aluminum bushings closest to the pinion flange pictured below)

These are the ones that without a doubt, get the hottest and by now just about every IRS Cobra out there has probably got worn out, looser than ever bushings.

OP's solution is obviously the low buck version, and hopefully his pinion angle is OK.

Not only do they clunk but they also contribute to wheel hop.

Here is the solution I used.:-D Full Tilt Boogie Racing

What are those strips of metal on your IRS brace, and what are they for? Mine doesnt have them:shrug:

 

[benulis55]

they're the axle ID tags. they are on the bolts from the factory on every pumpkin, he installed the brace and kept the ID tags visible

 

[97StangSVT]

I just bought my 04 Cobra last week from a dealer and it only had 6,700 miles on it. They also were experiencing the same problem and they thought it was the entire center section needing replaced. So they ordered a new one, along with bushings. They replaced the bushings first and it fixed the problem, so they returned the center section. In doing this, they gave me $1400 off the car since they didn't have to replace the center section!

 

[frank700]

LMAO! The same thing happened to me. I put it up on the lift before I bought it. Looked it over. They didn't want to touch the car or fix it. So I bought the car. Got a huge deal on it. Car is mint but they thought it had a major rear end problem. It's an amazing car!

 

[pdm]

Wow. I'm amazed at how experienced people are fooled into thinking that diff problems can transfer that kind of noise into the cabin.

I've been rock crawling for a lot of years and have seen every kink of bust, break, rip, tear, crack, grenade you can think of, and only one thing causes "the clunk" - mounts/bushings

EDIT: OP, congrats on the insight and the fix!

 

[Jimmysidecarr]

they're the axle ID tags. they are on the bolts from the factory on every pumpkin, he installed the brace and kept the ID tags visible

:rockon::beer::thumbsup:

 

[testorossa1989]

Having the same issue it sounds with the drive shaft banging. Going to try what you said this weekend. GOOD THREAD!

 

[ac427cobra]

Hi guys, I picked up an 03 10th annv. a few weeks ago. Awesome car but had a very loud thumping banging noise coming from the rear end. It happened when you engage the clutch and power was transferred to the rear end. It was loud and you could feel it through the floor.

I searched and went through all the posts on this message board about the problem. Didn't seem like there was a sure fix. I jacked the rear of the car up. I removed the stock exhaust system yesterday to install a Magnaflow. I noticed all the backlash in the driveline. Not sure how many degrees it is on the driveshaft but seems to be excessive. I moved the square metal weight around that hangs below the front of the pumpkin. It moved rather easily. It also moved the whole pumpkin. I looked at the rubber bushing that are on the front of the pumpkin and noticed it was easy to create space between the rubber and the metal that is sandwitched on the front of the pumpkin. I am speaking about the two bolts that go straight up and hold the front of the pumpkin and the square weight hanger. I attempted to tighten these two bolts. They were as tight as they could be. So I needed something to shim theses bushings that are to soft and worn out.

I went to the hardware store and purchased two 3/4 inch washers. $2.60. I took a grinder and cut a slit out of the washer so I would be able to hammer it in between were the rubber meets the aluminum on the housing. I rotated the pumpkin forward to create the space needed to begin to insert the washer. I hammered one washer in on each side. They fit well. Finished exhaust.

Test time.
Started car put it in first gear. Nothing. I went forward and reverse. Nothing. Went out for a 15 mile drive. Not a sound. So long story short because of the rubber mounting bushing on the front of the differential being wore out and probably to soft is causing to much play, slack causing the noise. I know it may be hard to understand without pictures. Sorry. But this is no doubt causing some of the noise related problems in these cars. Hope this is of some help.

Take care

OP:

Instead of fixing the problem, you just masked the symptoms with a band-aid.

Shoot me a PM when you're ready for the real fix that's been track tested for durability!

:thumbsup::coolman::beer:

 

[QuickV8]

i'm gonna try this.

someone mentioned a clunking noise. i had a clunking noise a few times but i figured it was my axle nut? could it have been something else?

 

[QuickV8]

can you post the direct link to the fulltiltboogie product.