Repair Information for Your Imperial's Rear End Noises and Vibrations

Imperial Homepage -> Repair -> Rear Axle -> Noises/Vibrations

Question from Quint (1953):

When I drive my 1953 Chrysler Custom Imperial, at times, when I am making a turn or a bend in the road and or I drive over a bumpy spot in the road, I hear a hollow noise, like something is rubbing against some hollow metal, like a trash can would sound if it were rubbing against metal. That's the best description of the noise that I can give. It happens intermittently, not all the time. At first I thought it might be the car bottoming out and I was in need of new shocks. I was ready to buy a set of four gas shocks but decided, after reading so much good advice on the IML, that it would be prudent for me to put this on the IML site and let you all take a shot at diagnosing the problem. Heck, maybe it isn't the shocks at all...although I'm pretty shore I have to replace the shocks anyway. Anyone have any ideas of what may be causing that noise?


From Chris:

Check your exhaust system for contact with the driveline or axle.

From Chris:

With the car cold, crawl underneath with a flashlight. Look for things that can move that are close to other things, and then look for shiny metal indicating that contact is being made. For example, where the exhaust routes over the rear axle. Or where the suspension parts approach other items. That'd be where I'd start...

From Keith:

Seems like we may share a similar problem! I will tell you what I have found and maybe it will help you. I have a '70 LeBaron that I broke two motor mounts (damn lead foot!) so I followed the advice of Car Craft magazine and fabricated a brace. It worked amazingly well = ) All was fine till I replaced my transmission mount (most of the rubber fell out). Instead of replacing the entire mount (which was not in stock) I replaced the insert (saved me some money and was in stock). Then I noticed several things at about the same time: 1) A noise that you described quite well but only when I make a hard left (damn lead foot), 2) trans mount insert shifted out of the mount, 3) Right behind the first u-joint my driveshaft is hitting the floorpan!!!! Before I replaced the trans mount I never noticed the noise so it must be that! I also noticed that my exhaust rattles on something when I am idling in drive.

From William:

If it's from the rear, it could be shock mounts (deteriorated rubber bushings) or perhaps the exhaust pipe being too close to the shock(s) as the suspension moves up and down. If, perhaps, one of the shocks has leaked out an amount of fluid, that might cause a rattle too. Might also be something like the rear door latch strikers needinig some tweaking for a tighter fit of the door(s)? Depending on the exhaust system hangers, it could be one of them that has deteriorated/failed, letting the pipe(s) drop down too far.

While you're under there, with the car safely parked and supported with sturdy jack stands, you might check the exhaust system for movement by lightly hitting it with the heel of your hand or taping on the shock absorber body with your finger or a mallet--trying to duplicate what you're hearing.

Question from Philippe (1957):

As I worked under my car today, I checked the propeller shaft angles with a homemade tool. For 2 1/2 years, I have a bad vibration, exactly between 40 and 45 mph (and another at 80 but I don't run the car often at such speed). The vibration occurs everytime I'm between the two values, if I'm in accelaration or deceleration phases. It isn't a very hard vibration but it is noticeable so I think there may be two problems (the wheels are ok):
- unbalanced propeller shaft
- problem of working angles

The FSM (and service reference books) are not very clear : I've measured the two (rear) angles, what do you think of them?

The service book says it should "not over 3°". Seems that I'm higher! I've verified that the two propeller shafts are "in line" with the "O" mark which is indeed rather not noticeable.

Should I install "tapered shims"? Where can I find them? Are these shims only a "wedge" of 2° angle ?

I think that I have an unbalanced propeller shaft condition but perhaps you have some more info?


From Brooks:

It's possible that one of the shafts is unbalanced. I know you're in France, but over here in Dallas, TX there are all kinds of places to go to get prop shafts balanced. Perhaps you have at least one around.... I know this because I own a Jeep. If you have 4-wheel drive clubs over there, they are using vehicles that constantly have to have prop shafts "made". Again, over here, those are everywhere, and very reasonable. If you can find one there, you could at least have your shafts checked for balance.

Beyond that, have you disassembled them to make sure that all the cups on all the U-joints actually feel very smooth as you rotate them with your fingers? Also, do that with the center bearing. Is it tight, or can you wiggle it around, thus changing the angles under acceleration? And is the rear transmission/engine mounting tight? Remember, it's one thing to measure the angles while you're sitting still and the motor's not running. How they behave under accelleration / decelleration could be a different situation entirely.

Beyond that, if you do have to use the shims, I believe you could (here again) get what you need from a 4-wheel drive shop and modify it to fit. Because we lift our Jeeps and things, that changes all the drive line angles. On my own Jeep, I added a 4" lift kit, and after that, I had a vibration in certain ranges and could not keep the rear U-joint in it. I had the rear u-joint changed to a constant-velocity joint (you could have that done too, at the same place that will check/balance the prop shaft) and that fixed that. Other people add shims (sold at 4-wheel drive shops) between the axle and the spring pack, as shown in the FSM references you gave. And like I said, maybe they could be modified to fit the Imperial. Or at least used as a pattern to make whatever you need.

I'd also check that front prop shaft angle really good, because it could be corrected pretty easily by adding shims under that rear engine mounting. It's possible it started out like that years ago at the factory, with shims under it, and somewhere along the way, somebody replaced the mount (or the transmission) and didn't notice that there were shims or forgot to put them back, and here you are.

Here is a link that shows pictures of the wedge-shaped shims for sale on a 4WD site. There's all kinds of other parts, but search in this page for part # 4529536 and the photos and description are above that part #. One of the shims pictured is standing on its side so you can see what it looks like.

From Paul:

If due to the drive shaft angle, this vibration will only occur at the lower speeds. This can usually be corrected by adding or removing shims between the center bearing in the drive line and its mounting point.

If there is a vibration, and there is a pile of shims in that location, the vibration will probably go away if you remove them. This has been the case with the two cars I had that did this. They were my '56 and my 1960 Custom.

The '60 did it after my father replaced the rear leaf springs with heavy duty leaves, and also added an extra leaf. Thusly, he raised the back of the car higher than its original position. That caused the out-of-alignment condition.

The '56 did it when I first bought it, but I noticed that it would go away when there were several people sitting in the back seat. When I removed the shims it smoothed out and never vibrated whether loaded or unloaded. It also had both rear axle support struts broken out, but the vibration was still there when I had them repaired.

I think that this happens because there may have been additional shims between the rear axle support struts, and their mounting points. At some time in the car's history, the struts had become broken, and the shims lost or discarded, throwing the whole thing out of wack. I have seen many Imperials where these struts were broken. I think there were shims in all three positions on the '56 models (first year of split drive line), but I think that they are mainly found under the support bearing on the newer cars.

Basically, if you raise the rear end, you have to take out some or all of the shims under the support bearing. The angle can be checked by following a procedure in the shop manual.

From Kenyon:

It is my guess that you took your car completely apart for the restoration.
If you did, then maybe you took your two driveshafts apart when you did?

If so, did you mark them and re-assemble as they were when they came off the car?

They were balanced at the factory to go together one way, and only one way as far as I know. Is it possible that you re-assembled them in a different way than originally? Is this what you mean by "being inline with the O mark"? I am assuming that this is what you're talking about, but if not would be the first thing to look at.

If it is correct, I would look at balancing wheels first, as they should be balanced anyway, and they are easy and cheap to do by comparison to the driveshaft.

I will also assume that your driveshaft bearing isolator that holds the driveshaft in a bearing in the middle is OK? Check that by pulling and pushing with light on it to inspect? Probably not that.

Follow-up from Paul:

I had a similar vibration in my '62 LeBaron last summer. It only happened at exactly 60 mph. It wasn't there below 60 or above 60. My front end man said it was the drive line and my transmission man said that it was the front end. I had the front end rebuilt, tires balanced, checked the front wheel bearings, replaced the transmission mount, u-joints, center support bearing and mount. Nothing made it go away. I didn't feel bad about doing all of that stuff to the car since it was all old and worn anyway. I did not have the drive shafts balanced. I knew that the vibration wasn't there before, so that wouldn't have changed.

It turned out that one of the radial tires had something wrong with it. It was on the right front. I still don't know what was wrong with that tire. It was not out of round, it didn't have a "bend" in it, and it was in balance. I had all four tires balanced five times. It never felt like it was only emanating from the right front of the car. Out of desperation, I bought a new set of tires, and the entire problem went away. In addition, due to the fact that I had all of that other work done, the car drives better now than it has for the whole 25 years that I have owned it.

Question from Tristan (1968):

The rear end in my '68 convertible is quite noisy, it whines on the highway from about 45 mph on up. It's a limited slip Mopar 8 3/4 out of a '67
LeBaron. I can get another rear end, but it's out of a '68 Fury, and the bolt pattern is wrong for the wheels. Also it is a non limited slip unit, and I hate to lose that feature. Is it possible to take apart the carrier, and bolt the crown gear and pinion out of another rear end into this one? or put the clutch pack from my rear end in the other carrier?


From Dick:

Tell us about the whine - when does it occur (acceleration, deceleration, float, corners etc.) Also, is there any leakage from the front seal companion flange area? Are you sure the rubber sound isolation parts are present on the spring/axle mountings. Is your trunk top well and carpeting all in good shape - noises from the rear of a convertible are often due to missing sound insulation/barriers. Maybe we can suggest a cure with less radical effort required.

As for swapping parts from one differential to another, I'd be afraid to try it (and I'm pretty brave!); they are really tricky to set up. If you have to replace it, I'd swap the whole unit intact. I'm sure you can find a replacement rear end for your car from one of the IML vendors on the list.

From Elijah:

Before you go diving into the rear end, have you eliminated the axle bearings as the source of the noise? I've had to replace the rear axle bearings on two of my Imperials in the past year (and still have one more to go!). The '70 Imperial that I bought last year had a LOT of noise from the rear, which proved to be from the axle bearings.

An easy way to test is to drive the car at a steady speed where you're getting lots of noise from the rear, and then turn the steering wheel enough to shift the weight of the car from side to side. If the noise "shifts" sides or seems to move around, it's probably axle bearings. Take someone along as an extra listener!

Replacing the axle bearings is relatively easy. There's a local machine shop where I live that will press the old bearing and seal off and press the new ones on for $25 per axle. The bearings and seals (outer and inner) are cheap. Pulling the axles is easy on '65 and newer Imperials. The only "tricky" part to re-installing is to make sure the axle shaft end play is properly set (if not, you'll soon be doing it all over again).

From Demetrios:

My '68 sedan developed a nusty gear oil leak and contaminated the right drum. I asked my local mechanic to do the job, and he did both sides (don't ask me the cost, too damn expensive). As I recall, in the limited slip rears (as on my '68) there is a little cylindrical part between the axle and the gears. It looks like some sort of a spacer. In my car, it was not there in one of the half shafts, but it was there on the other. Apparently, the rear end was worked on sometime before, and the person assembling it paid no attention to that part. When the work was finished (new seals and bearings) the car made a similar sound as you describe. It starts at about 40 mph and continues at higher speeds (well, over 90 or so you can't hear it due to the wind noise from the shot weather stripping, but I think the sound intensity drops a bit with speed). I doubt that restoring that little part is responsible for the noise. I was told that the noise has something to do with the gear adjustment, and also that it has no effect on operation of the gears. On second thought, may be restoring that little part changed the gear alignment or something. Over the years (I think this happened 2 or 3 years back) I think the noise level is slowly dropping. Or, may be you can say I got uset to it, but I drive my LeBaron most of the time lately, so I would not get used to the noise. In short, even though anoying, I do not think this is worth worrying about, and the noise will probably become less intense as the miles accumulate.

The spacer was found inside the gear housing and reinstalled. May be reinstalling the spacer changed the gear meshing somewhat and produced the noise. And as the miles accumulate, the gears readjust through break-in.

By the way, the Fury may have different gear ratio. All imps of that era had 2.94's. The Furys had either 3.23's or 2.76's as far as I know. I would not recommend the 3.23 unless you like smoking your rear tires and drag racing. The 2.76 will give you taller gearing, but I think it may be too tall for the weight of the car. You can compensate of course by using 70 series profile tires.

From Bob:

Are you sure they used the correct gear oil? There is a specific gear oil for Limited slip/ Posi rear ends. I have heard the wrong oil can cause noise.

From Paul:

When my Dad turned their 1960 over to me in 1985, he had just replaced the differential with a rebuilt unit that he paid a lot of money for. He didn't know it, but after that the car had so much rear end noise I had to turn up the radio to hear the news.

The noise was the same as what you would hear with a heavy set of snowtires only 10 times as loud. It did it all of the time. The faster you went the louder it got.

I finally found a guy in the Seattle area that did differentials for a hobby. I don't remember his name, but at the time he was well known in our area. He had a unit that he had rebuilt and gauranteed would work smoothly and quietly. I bought it, had it installed, the car was fine.

I also wanted to know what was wrong with the other one. It was a Sure Grip. He took it all apart, and said that it had new parts in it, but the gear adjustment was way off. The ring gear and the pinion gear were not meshing properly. He also found some other things, but he felt that was the cause of most of the noise. He rebuilt it and I hung on to it.

Eventually the differential in my '65 Crown went out, so that is where it is now installed. It works perfectly. It was real handy to have it all ready to put in when I needed it. Come to think of it, I may have had the one of the '65 rebuilt too, I might still have an extra one for when I need it in my '62.

Differential trouble is not uncommon. I have had to work on several of my cars over the years, including my x-brands. The one in my '81 Buick Electra completely failed at 121,000 miles.

Question from Chris (1970):

I have a '70 Imperial LeBaron w/ a moaning sound comming from the rear. I purchased it back in December w/ bias ply tires (which are still on it....but I plan on changing them in a few months). The sound becomes noticeable above 15mph and was wondering on any ideas. I'm thinking I have a bad bearing in the axle and would like to replace all of them in one shot. Any helpful hints or suggestions would be appreciated. Also, if you know of any quality vendors for parts (like a quality rebuild kit-seals and bearings) that would be great.


From Elijah:

You're probably right in your diagnosis of an axle bearing. If the sound changes as you go around a curve (i.e. seems to move from side to side), then that's definitely it. However, BEFORE you tackle this, be sure to check the fluid level of the differential -- it might simply be a bit low.

Replacing axle bearings on these cars is pretty straightforward. If you have a shop manual, follow the instructions, and you can easily do it in an afternoon. I just performed this procedure on my '70 LeBaron last summer.

The only "trick" is to make SURE that the axle shaft end play is adjusted properly, AND to be sure that the locking clip for the adjuster is installed correctly. On both my '71 and '70 Imperials, I have had rear axle bearing failures -- and on both cars, I found that someone in the past had failed to correctly adjust the end play and/or install the adjuster locking clip.

From Kenneth:

The moning is spider gears,they need replacing,its probably an 8 3/4 rear;inthat case, you replace the carrier.The carrier is pretty in expensive so go that rout.

Question from Robin (1972):

Checked the end play on my axles today and I had about .027". Pulled the right axle to check the bearing. Looks and feels ok. Will repack it and reinstall and then do the other side and reset the endplay. I have a vibration in this 72 Imperial that I cannot seem to find. The bearing race number, for general info, is Timken M201011.

Reply from Chris:

Have you checked the gear lube? It might be a set of bad tires. I just put on a new set and it took care of my "moaning in the rear."

Question from Roger (1974):

Have a vibration in rear end of my '74 Imperial. I changed the tires to new ones, checked and replaced out of the round rims/wheels, tires balanced by a very good shop and checked at another shop. Vibration starts at about 60 mph and gets worse at about 65 mph and seems to fade at 70 mph. The car has shure grip rear, any ideas or suggestions how to check this problem out?


From John:

Its possible the problem is a failing u-joint.

From Roger:

Check your wheel bearings and U-joints.

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