*BANG* coming from the rear of the car - thoughts???

[DMage]

Of course we have a car show coming up this weekend and after some evening work with Morpheus we fixed up my clutch master and slave, as well as the brake booster line. Took the car for a spin and was greeted with a loud BANG noise from the rear of the car. Pulled over, nothings loose, wheels are on tight, shook the car every which way we could - nothing seemed wrong. Checked engine mounts and they look good - engine was hot but tried shifting it and it didn't budge.

Noise is loud, startling even. Its random - happens at a cruising 35mph, seems to happen more when going around corners or over bumps. Doesn't happen when shifting.

Suspension was replaced within the past two years with DMCH shocks, DMC Europe front springs. Thought it might have been a blown shock but doesn't make sense from the noise and randomness when we heard it.

Our thoughts were a CV joint had gone bad, or a bad wheel bearing. Any other ideas?

Was going to jack up the rear tomorrow and spin the wheels to see if I can reproduce anything.

[mluder]

Are all your tools accounted for?

Steven

[DMC3165]

Is the bang accompanied by a jerking or lurching? If it is it might be the differential? Could also be yor TABS. Mine sometimes makes a mild thud. But its been checked and rechecked so I'm content to live with it.

[WelmoedJ]

Check the supports of the gearbox.
Perhaps one is broken, though that usually is noticed by unability of using some of the gears (of a manual).
In my car the left support broke resulting in no 3rd, 4th and 5th gear.

Don't know if yours is a manual or auto.

[jmettee]

Was this a single bang (one occurrence) or is it repeatable? If repeatable, most concerning would be a broken TAB. I drove for a short distance at speed after mine broke (about 35MPH to stop in 100 feet or so). A broken TAB would mean 1 of your rear wheels is not firmly held in place & the rear of the car would feel "soft" - it would wobble & sway.

[DMage]

No lurching or jerking. Was just under the car last night and no broken mounts. The bang happened once prior to last nights work on my last trip home with the car previously, and I had assumed it was just a pothole. Tabs have been replaced with Tobys tabs.

[Morpheus]

It has no rhyme or reason, and most of the time it was 2 bangs in succession. While under the car last night, I noticed that the CV joints closest to the wheels were semi-moist. Also, to my knowledge, his rear wheel bearings are OEM.

[David T]

Can you make it repeat and under what conditions? Is it a mechanical noise? This is really difficult to help with. Check the mounts on all of the shocks. Check the sway bar brackets and mounts. Check the lug nuts. Could it be the motor backfiring? Can it be something moving around in the truck?
David Teitelbaum

[DMCMW Dave]

It has no rhyme or reason, and most of the time it was 2 bangs in succession. While under the car last night, I noticed that the CV joints closest to the wheels were semi-moist. Also, to my knowledge, his rear wheel bearings are OEM.

Is it happening when you change direction, i.e. turn left or right for the first time after the opposite direction? Rear wheel bearing shifting in the carrier is a pretty common complaint.

[DeLorean]

Are all the frame to body bolts tight?

[Morpheus]

Is it happening when you change direction, i.e. turn left or right for the first time after the opposite direction? Rear wheel bearing shifting in the carrier is a pretty common complaint.

We were driving straight when it happened most of the time. We drove around a parking lot making sharp turns and, while we heard a few clunks, it wasn't the same sound as the very loud BANG BANG we heard while driving normally.

[DMage]

Can you make it repeat and under what conditions? Is it a mechanical noise? This is really difficult to help with. Check the mounts on all of the shocks. Check the sway bar brackets and mounts. Check the lug nuts. Could it be the motor backfiring? Can it be something moving around in the truck?
David Teitelbaum

Rear shock mount nuts are in there and double lock nut secured. Rear shock mount to lower arm is secure. Lugs were tight, checked that in the parking lot. Noise is coming from rear so not sure how the front sway would impact it. Trunk was empty. Could it be a backfire? I guess its possible, but the engine idles perfectly and has for the past 7 years I've owned the car. Still has the mixture plug sealed. The only difference recently of things I have done to the car are replacing the gas with non-ethanol 91 grade gas. Would that have an impact on a backfire? I wouldn't think so. This sounds more like a mechanical / metal bang then it does like an explosion.


Is it happening when you change direction, i.e. turn left or right for the first time after the opposite direction? Rear wheel bearing shifting in the carrier is a pretty common complaint.

I've heard that noise before, and this is much louder and more random.


Are all the frame to body bolts tight?

I can check them, but we did push and move the car every way we could and had no movement.


We were driving straight when it happened most of the time. We drove around a parking lot making sharp turns and, while we heard a few clunks, it wasn't the same sound as the very loud BANG BANG we heard while driving normally.

And when we left the parking lot I was cruising in 3rd gear at 35mph and it did it. We were going on a slight left gradual curve at the time.

[Evildeli]

. Could it be a backfire? I guess its possible, but the engine idles perfectly and has for the past 7 years I've owned the car. Still has the mixture plug sealed. The only difference recently of things I have done to the car are replacing the gas with non-ethanol 91 grade gas. Would that have an impact on a backfire? I wouldn't think so. This sounds more like a mechanical / metal bang then it does like an explosion.



When I start my D up, I usually let it run idle at least 6-10 minutes before driving. If I rev the engine before the 3 minutes marks, most times I'll get a misfire pop. However I never get that pop after the 6-10 mark. You said the engine was hot, so I would guess it's not backfire. Just my guess though.

[Ryan King]

My vote is on a CV Joint

[stevedmc]

This is one of the benefits of being single and having no kids. When my car makes dangerous sounding noises I just keep driving. If/When I die, it doesn't really matter.

In all seriousness though, I would check your TABs and all the other stuff everyone is mentioning. TABs were my biggest fear when I got my car, and upon inspection I found one had rusted in place and was bending. At the time I had a girlfriend and it really would have sucked to have had something bad happen while she was in the car.

[David T]

You could try jacking up the rear tires and running the car in gear while you carefully go looking for the source of the noise. It *could* be a C/V joint. At this point it can't hurt to pull the half-shafts, disassemble them, lube them and replace the boots. Make sure all of the bolts in both half-shaft to output flanges are in tight. Check the oil in the transaxle. If it is a backfire you might notice a momentary loss of power in the gas pedal.
David Teitelbaum

[DMage]

Thanks. Going to give that a shot tomorrow night as well as crawl all around under the car again - but being just under there yesterday for the slave replacement, nothing really stood out.

Oil in the tranny should be good, replaced it several years ago and my case has no leaks.

Another thing, not sure if its helpful - I've had a noise for the past few years (car doesn't get out much - maybe 1500 miles in the past two years) in the rear of the car on the highway. Sounded like brake pad clatter, and went away when tapping on the brakes, but it was definitely RPM related. Was a noticeable but quieter clicking noise. I did several things to try to stop the brake pads from clattering but maybe it wasn't the issue and is related to this?

[DMCMW Dave]

It's a hard one to spot but I've seen trailing arm bushings fail and do this. You need to remove the trailing arm bolts and check the bushings.

[DMage]

It's a hard one to spot but I've seen trailing arm bushings fail and do this. You need to remove the trailing arm bolts and check the bushings.

Can do, will check tomorrow, thanks for the idea. That makes sense as I assume it would bang around in the frame if the bushing went. Should be easy to get the Toby Tabs out.

[DMage]

Wanted to wrap back around to this - the issue was discovered after poking around under the car for several hours on Friday. The upper bushing on the DMCH drivers rear shock split in half and was sitting wedged between the frame and the pontoon. The shock must have been rolling around in the hole and banging back and fourth. Luckily there was less than 2 miles put on the car since hearing the noise and just driving it around the neighborhood, so I imagine any damage is minimal to the shock or the frame. Talked to Stephen at the Celebration show on Saturday and will get a new bushing sent out sometime this week.

[EdFerri]

Just to throw this out there..... Do you have any loose tools in the small compartment behind the drivers seat?

[DMage]

Just to throw this out there..... Do you have any loose tools in the small compartment behind the drivers seat?


Wanted to wrap back around to this - the issue was discovered after poking around under the car for several hours on Friday. The upper bushing on the DMCH drivers rear shock split in half and was sitting wedged between the frame and the pontoon. The shock must have been rolling around in the hole and banging back and fourth. Luckily there was less than 2 miles put on the car since hearing the noise and just driving it around the neighborhood, so I imagine any damage is minimal to the shock or the frame. Talked to Stephen at the Celebration show on Saturday and will get a new bushing sent out sometime this week.

See prior post.

[EdFerri]

Damn bushings....!
Glad you got it all figured out!

[DMage]

Damn bushings....!
Glad you got it all figured out!

Me too! Damn bushings is right! Torqued em down to spec but from the looks of it the bushing wasn't seated straight and may not have had the full lip in the hole. :(