When I was driving in to work this AM in my 79', I was on the highway and had let off the accellerator and as I started to press the gas peddle, I could here a loud and fast popping noise that sounded like something was knocking against the underbelly of the car as I was accelerating, right around the middle of the car.

I let off the gas, and then when I went to press it again the noise was gone. A couple of miles down the road, off of the highway, I hit a pothole, then when I pressed the gas I heard it again, then it went away after I let off the gas.

From earlier posts, I discovered that I am missing a rear bracket (right behind the bumper) that helped hold my driver side exhaust pipe in place. As a result of the missing bracket, sometimes I hear my tail pipe popping off my bumper. This is not the sound I have been hearing.

However; when I play with that driver side exhaust system, I can see that as a result of the missing bracket the whole thing can sway back and forth a little bit. But, I've been missing the bracket for sometime and I'm only now hearing the noise.

Anyone experience anything like this before?

P.S. the engine is working fine and this sounds more mechanical than anything else. I apologize if I put this in the wrong forum, but since I'm really not sure where the problem is I figured that this forum gets the mosts hits so I put it here. Thanks for any advice/suggestions I can get...

The first thing you should do is secure your tail pipe. Just because it did not make noise before does not mean it has not broken another bracket and now hits something else. Once you have corrected that problem you should check your catalytic converter. The older ones tend to break up inside which causes a pretty loud rattling noise.
Harald K

Do me a favor so we can cross this one off the list of possibles...reach up and grab the drive shaft to see if you've got any play in your universals.

I tried to move the drive shaft and couldn't get it to move any. However, the more I read about it, I think it must be the universal joint. The maintenance manual seemed to nail it right on the head. Once I get into into the last gear, I let off the accelerator, then when I go to accelerate again, I hear the knocking start up again.

When I was on the highway, I threw it into neutral and the sound went away. When I travel in the first two gears I have no problems, and even when I'm travelin around forty/forty-five I have no problems.

If it is the universal, how expensive and timely is the repair? Also, how long can I continue to drive with it in bad shape. That's not my plan, but I do have to work all week and it's my one and only right now.

If you grab the driveshaft near the front and rear universal joints and twist you should be able to get a perceptible movement if the u-joint is worn/damaged. If its bad enough to hear a loud banging noise I am sure you will be able to detect it, but to me it sounds like something else--maybe that loose exhaust system. If you have to replace the u-joints it is fairly simple if you have a ball joint press or a large bench vise, other wise take the new joints and drive shaft to a repair/machine shop and let them press them in. Make sure you orient the new joints crrectly or you'll get a vibration and don't overtighten the caps!

Another thing it could be is play from your pinon bearing in the rear end. As they wear it will move back & forward making a thump when you hit the gas or let off.

I went back and checked the drive shaft w/ the car in nuetral and I can twist it back and forth with ease. That's definitely not my only problem, but that must be the noise. One of my older buddy's at work thinks that my rear end is shot too. Still need to jack it up for more assessment.

Now, it's my daily driver and my only car, so should I take it to somebody for the fix, or will I save drastically by doing it myself? Keep in mind I have no sure fire way to jack it up myself but was looking into getting the ramps that you can find at the Pep Boys, etc... I know the u-joint itself isn't that much, but what kind of time frame and tooling am I looking at?

I'm beginning to think I got in a little too far over my head with this one. I certainly enjoy the El Cam and would like to own at least one for the rest of my life, but right now I have very little $, no garage, no tooling, no real mechanical know-how, no body/paint experience, and an el camino that requires all of those. Might just get a new car and set the El Cam to the side for a couple of years until I can mark some of those items off my list.

If your description is accurate, I think Harald K is on the right track. With an exhaust pipe hanging and swinging back and forth, who knows what the noise is coming from. Maybe a muffler is moving and being whacked by a u-joint? You can secure the exhaust pipe and muffler with a couple of coat hangers or mechanics wire for now to eliminate it as a problem. If its the rear end with too much play, with the car in neutral and the car on the ground, when you turn the driveshaft back and forth, you will be able to feel it and maybe hear it. It also doesn't sound to me like a u-joint. In my experience, a bad u-joint usually causes a vibration that you feel in the seat of your pants and doesn't make a "banging" noise. Good Luck.

Don't be discouraged to quickly. While u joints do go out from time to time, under normal driving they usually last quite a long time the same holds true for the rear end if it has lubricant in it and has not been abused it is probably still ok. The kind of noise you described is not usually associated with either of these parts. Like I said earlier the first thing you should consider is to secure that wondering exhaust pipe and then go from there. These cars are pretty durable and you will usually wear out the motor well before you wear out the rear end. One thing I would invest in is a good shop manual. If you check the swap meets or the inter net you can find complete shop manuals for G-body GM cars for a very reasonable price the actual factory manuals even help you diagnose different noises. If the car is still running pretty well it is easier to keep it that way, rather than to park it and resurrect it later. Besides you can learn by doing. Take your time and research things before you run out and spend money. Use the junk yards for a good part source. get to know your local car club, use the internet forums. You will be surprised at how much you can learn about these cars. One of the reasons you still see so many on the road is because they are pretty hardy and not that difficult to work on. Lastly take car of what you have until you learn more about the car nurse it along. Good luck Harald K

Everyone one on this forum was young and inexperienced and most of us had no money, no knowledge and no garage. Don't be discouraged. First of all I really think that you jumped the gun on the druveshaft and rear end. I remember that when I was an inexperienced fledgling mechanic I almost always assumed the worst instead of looking for the simpler and more obvious. Take care of that exhaust system it is more likely to cause a "banging" than a rear axle. Also get yourself a repair manual; at least get a generic manual that you can purchase at a autoparts store but prefably a factory manual (try Ebay). And lastly accept advice from your friends with a great deal of skepticism unless you know that they are related to Smokey Yunick and inheirited all his genes.

Check the Body Mounts just behind the doors. According to some of the posts here it could be that mount is shot and ratteling against the underside of the body.

Your driveshaft should have a small amount of play associated with it, taking into consideration the preload of the rear end. If the U-Joints move, not the shaft but the bearing surfaces rattle then its that if it rattles a little with movemebt in the rear yoke that is normal up to about 1/16th" or so.

U-Joints are about 1 hours work if they have never been changed from the factory. Those you have to use a torch to melt the plastic bindings installed from factory. Heat the U-Joint Trunion not the actual caps, until you see the plastic spew out the holes. Then before it cools off much knock out the caps using a 1/16th" deep socket or something about the size of the U-Joint cap and a good heavy hammer.

The new U-Joints will come with locks that snap around the inside of the cap bottom. There is a groove there. After you put the clips on use that hammer again to seat the caps/clips, A small stiff tap in the cas back and forth should do the trick.

You can get "Pre-Lubed" U-Joints or U-Joints that have a grease cert for lubrication during its life. Once you've done the job its no longer a mistery. Set the shaft on a block of wood when beating the caps out. If you have a press that makes it way easier but if not a socket will do the trick or a Brass Drift pin.

Just some thoughts.

All,

Thanks for the posts and advice. I'm gonna try not to get too discouraged. I think I'm gonna buy a new car tomorrow anyway. That isn't going to deter me from still working on the El Cam, it's just going to alleviate some of my day to day transportation issues. I was already looking at new cars, but this latest problem has hurried the process a little bit.

The friend I mentioned was looking at my car and started rocking the el cam from side to side using his foot on my rear wheels. You could hear a popping sound as the el cam started rocking. From this I think he's convinced that my wheel bearings are shot. Could that be making the noise previously mentioned?

PS I do have a Haynes Repair manual, but when I read up on the U-joint change it seemed a little advanced for me (Since currently I have no way to jack up the el cam to do the fix). Anyway, again thanks for the posts and encouragement, and once I get enough time and find a way to jack it up, I'll let you know what I figure out.

Ethan, DO NOT put your Camino on ramps & disconnect your drive shaft! This is a recipe for disaster. Invest in jack stands. If you must use ramps, make sure you chock the wheels & have a very reliable emergency brake. Disconnecting the drive shaft is like putting your car in neutral. Jon

Good advice. I remember jacking up the front end without setting the handbrake or chocking the rear wheels. The car was on a slight slope. Everything would have been ok except it was my wife's minivan which is front wheel drive. It rolled down the driveway and into the street--luckily no traffic.

You can get a decent set of cast iron jack stands and several different floor jacks are available from Harbor Freight Tools. They have retail stores now as well as catalog sales and internet sales available. I got a set of 3 ton stands for right around 15 bucks at one of the retail outlets. I bought one of their floor jacks for about 20 bucks years ago and it's still going strong. I wouldn't own a set of ramps personally, while working on the ex's car at the base hobby shop one evening, ( I was on a creeper under the car ) a guy three bays down dropped his drive shaft, no parking brake, and it rolled off the ramps hit the ex's car and it pushed me and the car across the garage. If I hadn't been on the creeper my chest would have been crushed by the wheels. Safety is everyone's business.

check your transmission mount and engine mounts(easy with two people, put it in gear and powerbrake it a little while watching for too much movement in both drive and reverse)

also check your Torque converter bolts where the converter bolts to the flywheel and if possible check the flywheel for cracks(more common than you think)

if it is not a totally metallic pop it may be gas getting past the plug and detonating in the pipe or converter..check all plug wires/rotor cap/plugs

Like someone else said, it may be the exhaust getting rubbed by a u-joint

Good Luck

I bought a new ride the day after my last post on this thread and I haven't posted since until today. I've been ashamed to come back. I haven't even started up the el cam since I got the new ride either... I feel like a cheating spouse.

Anyway, I'm just now getting back to a little surplus cash mode and the girlfriend's moving in June so I'm gonna get back to work on the El Cam. Still have the same problem I'm sure.

I'm gonna take the advice and wire up the exhaust, but as I said before, I'm sure that wasn't the problem. I may take it by a local mechanic to get their opinion on what the deal is. Anyway, I'm gonna take Harold K's advice below:

If the car is still running pretty well it is easier to keep it that way, rather than to park it and resurrect it later.

BTW, I got a 2004 Scion Xb. Funky little toaster but hey, I'm making bread...

I wouldn't own a set of ramps personally, while working on the ex's car at the base hobby shop one evening, ( I was on a creeper under the car ) a guy three bays down dropped his drive shaft, no parking brake, and it rolled off the ramps hit the ex's car and it pushed me and the car across the garage. If I hadn't been on the creeper my chest would have been crushed by the wheels

Now see I am just the opposite. I was under a car that fell off jackstands and came within about an inch of having my chest meet my backbone. I was very lucky but I won't work under a car that is just up on jackstands. I don't trust them anymore. I like Ramps, more surface area holding the car up than stands. 8O


Now as for:
Anyway, I'm just now getting back to a little surplus cash mode and the girlfriend's moving in June so I'm gonna get back to work on the El Cam. Still have the same problem I'm sure.

You actually believe that you will have both surplus cash and time to work on the car?? :D