How To Diagnose and Repair Noises and Vibrations Associated With Your Imperial's Driveshaft


Imperial Home Page -> Repair -> U-Joints & Driveshaft -> Noises

Tip from Brad:

After a recent transmission rebuild, I encountered a driveline vibration severe enough to make the ashtray bounce up and down at certain speeds; 30, 40, 60 mph.

I found the cause yesterday.

I suspected the rear u-joint and decided it needed closer inspection. When I got the rear of the car up on jack stands, I felt around the u-joint and noticed it felt like it wasn't centered in the yoke. I pulled the retainers and found this to be the case. But why had it slipped? some point in the past, someone failed to install the C-clips on the bearing caps! The driveshaft caps had them, but the yoke caps were missing.

I'm sure my transmission friend didn't pull them (C-clips) to get the driveshaft out, (they were caked with OLD grease) but I'm a little dismayed he didn't remark on this when he put the thing back together.

Anyway, I had to buy a new u-joint to get the clips. $8.00 at Autozone. I pushed the clips on, bolted it back and drove out for a test. Vibration at all previously noted speeds, GONE!

Silky smooth ride now, except for braking at low speed. I plan to turn the rotors next.

Question from Joe:

My problem is lately the 1st and 2nd gears have a large shudder feeling under power. There is also a weird sound emanating from below like a slipping sprag/tooth thing. Kind of a raspy sound.  When I mash it the trans shudders violently like it's coming off the mount that I just replaced. When someone looks underneath while under power the driveline isn't vibrating at all. Are the bands catching and letting go in a violent succession while under high torque loading? What do you think. Fluid is new. Doesn't smell burnt. Did the trustworthy 727 give it up for burnouts with a 5,600lb Imp?


From Tony:

It sounds just like my '61 coupe just before I replaced the Universal Joints. They're cheap, common and did the trick for me!

From Gary:

The 727 Torqueflite when left in drive does not use any band engagement in low gear. The sprague clutch does the job. That is why there is no engine braking in 1st gear when the selector is left in drive. When you move the selector to 1st, you engage the low/reverse band and it locks the 1st gear planetary unit and provides engine braking in first gear. If you get the shudder under full throttle while in drive, the problem is most likely the sprague clutch (overrunning clutch assembly). If it doesn't shudder when the selector is placed in 1st, then the sprague clutch is bad. >From what you have described, I would suspect that the car has weak rear springs and under hard acceleration, the rear axle is "wrapping up" and changing the drive line angle and causing the shudder. A tight rear u-joint will also render a similar symptom. At break away, the torque at the end the the drive shaft is considerable. Engine output + torque converter + transmission ratio somewhere around 2000 ft lbs.

From Kne:

A visual inspection of the U-joints should tell you if they are your problem--good call Tony--if there is no physical problems that you can see, grab a hold of the driveshaft (of course the car is off and the parking brake is applied) and twist it back and forth observing the U-Joint. Another simple test is to come to a complete stop on a level road, apply the brake lightly (just enough so that you don't move at idle, but not enough to prevent you from feeling what happen upon shifting).

Put the car in neutral and if you have been going forward shift into reverse (vice-versa if need be) upon shifting if you hear or feel or both a clunking sound, chances are that one or both u's are bad. In either case, always replace U-Joints in pairs, that is to say both, even if there is only one bad one. The addition of a new U coupled with a bad will only shorten the life of the older one, rapidly I might add. Besides, it really is easier to replace both, after all, the driveshaft has to be removed, might as well remove it once.

I seriously doubt that the ole '727' has given up, they are just about bullet-proof! I have jammed a 727 into reverse doing 80mph and did nothing but change directions of travel.

The Charger doesn't seem to have a problem from what you tell me, sounds like she's running about as good as she was built. What you are describing sounds like (unless there has been work done that your not talking about) not a transmission converter problem but a rear end. Depending on what size your Charger has determines what kind of hole shot you will get.

I use to drag race a 1965 Ply Belvedere with a 425 wedge that had a stock 323, great overall, but not for the strip. Changed to a top end gear and experienced exactly what you are, seemed slow out of the blocks but after 2nd, jumped like a jack-rabbit. To determine exactly what rear axle you have, crawl under and check for a small tag that is bolted to the pig (ring and pinion housing), it is usually on the back but could be on the front. Just a bit of trivia about my '65, in 1967 $ 68 I ran on the Detroit Dragway Dragstrip and turned 12.005 in the 1/4, Stock class. That was the fun days, before all the big money made it impossible for the backyard mechanic to have weekend fun!!!

Question from John (1956):

Just put the drive shaft back in my '56 S'Hampton, complete with new u-joints and center support. Santa Fe Auto Machine did an excellent job.

Now, here's the rub. The obvious drive shaft vibration and associated noises are gone, indicating that the shaft indeed wanted attention. But there is still a very pronounced vibration on acceleration at about 20 to 25 mph. It mostly goes away at higher speeds, but is still noticeable. I thought perhaps the problem was with the engine somehow, but when the tranny is put into neutral at speed, there is no change in the frequency of the vibration. Could it be the wheels, or the rear axle, or even the differential? I notice a pronounced "clank" when put into gear, both forward and reverse. Since the drive shaft has just been refurbished, I rule out that angle. What could be the source of my continued "vibra-bed" on wheels?

Reply from Mike:

Even though the driveshaft has been rebuilt recently, I wouldn't assume that the U-joint angles are correct. You might read up on the subject from a Chrysler Master Service Conference booklet we've posted on the club's website here.

In fact, on Page 10, Chrysler states, "When testing an Imperial (two-piece shaft), experience indicates that a vibration between 15 and 20 m.p.h. is apt to be caused by prop shaft misalignment (incorrect working angle), rather than shaft unbalance. But if the vibration comes in at speeds above 28 m.p.h., chances are its caused by an unbalanced condition."

Here's the direct link to that page.

Follow-up from John:

Thanks for the steer to the Chrysler Master Service Conference booklet page posted. I'll look into the working angle, and that may be just the problem. Years ago, I ordered a set of leaf springs and had them installed. They lift the rear end up, and the car sits high at the rear. After reading the repair pages on the subject, all the indicators point to a wrong working angle. I'll see if I can get the springs re-arched and bring the angle to specs.

It may be a while before I can get the car to Albuquerque, but I'll let the club know what comes of the fix when it happens.

Question from Jay (1962):

One problem that I have yet to solve is driveshaft vibration in our '62 4-door. About a week ago I received a newly rebuilt center carrier support from The Damper Doctor in Redding, CA. Few days later I got around to pulling the driveshaft out of the car. Ready to install the new mount? NOPE! The inner diameter of the new bearing was about 1/4 inch TOO LARGE!

My old bearing was fine, but I was looking forward to a fresh and completely new carrier assembly. I pressed the new bearing out and the old bearing into the the rebuilt mount. Put it all back together and....

The 100 pound woodpecker on "take-off" was silenced! (those of you with worn carrier mounds know what I'm talking bout). But now I had a VERY irritating vibration an nearly every speed above 40 mph.

The very first time I had the driveshaft out of this Imperial, I noticed that it was balanced. I had scratched some marks at various disconnection points to help me line everything back up EXACTLY as it was originally. This time around I had not paid attention to the scratch marks.

A few days later, I pulled the driveshaft out to line up everything the right way. I remembered discussions on the IML about the importance of the driveshaft alignment (which is adjusted using shims between the carrier mount and the frame) and this alignment's effect on vibration. I set the shims as they were with my previous mount (4 shims) and took t for a test drive.

The vibration was reduced, but still there anywhere above 40mph.

The next scene under the car didn't involve driveshaft removal (thankfully) but merely removing shims in order to try another alignment to see if it was any better. This time around I used two (2) shims.

The two shims netted better results. Vibrations now were *only* at 35, 60 & 85 mph respectively. This is the configuration that I am at today. I can now drive the car at constant speeds without too much irritation if I cruise in the "no-vibration" speed zones.

Does anybody have any suggestions on how I can go about setting the proper driveshaft angle correctly? I don't have any levels for that "special" tool that the FSM is always suggesting to use. I know that the gas tank needs to be full, supported by the wheels or suspension, and the car basically empty of passengers and cargo/luggage.


From Bob:

In the FSM for a '66 (and yours should be the same) there is no mention of shims or "special tool" for the two-piece Imperial driveshaft - that stuff applies only to the Chrysler one-piece driveshaft. The previous discussions on the IML were NOT correct. However, the procedures for servicing (replacing, cleaning, lubing) the u-joints are fairly detailed and seem to require some care. I'll defer, of course, to someone with exact '62 experience, but I'd guess your problem is not shimming or alignment.

Clarification from Chris:

Actually, there was a design change in 1965 on Imperial 2-piece driveshafts that allowed the elimination of adjusting shims used in the original 1957-64 design. In 1965 two constant velocity joints were added to the rear half of the driveshaft which meant the driveshaft angle was no longer critical and shims no longer used

From Dick:

You are barking up the right tree, but I'm not sure the result you want is ever going to fall into your hands by this sort of trial and error. My advice is to take the car to a "Driveline Specialties" franchisee in your area and let the professionals do it.

I almost never advise an owner to let someone else work on your car, but in this one area, I change my tune. The pros have ways of making things right, which include very fine adjustments on the positions of your transmission, engine and differential housing mountings which do wonders, especially on cars with center bearing supports.

Driveline Specialties have completely cured this type of vibration in my 47 Packard Limousine, my 55 and 56 Patricians, and my (now departed) 62 Continental and 69 LeBaron - all by simply optimizing all those mounting positions simultaneously.

They will probably start out by spin balancing your driveline components, and making sure the phasing is right at all 3 u-joint positions. Then they will measure and correct the angles that the centerline of the crankshaft/transmission and differential/pinion axes form. Then they will position the center support to lie exactly on that centerline.

Of course you can do all this yourself, but you need pretty accurate angle measuring hardware, and a lot of experience to get it right on the first try. Don't forget that no position of the center support bearing is correct if the engine/transmission is not aimed perfectly at the pinion axis, and this means not only vertically but horizontally. When the cars are put together at the factory, all of these things are set with precision; but the shim and bolt positions are disturbed over the years with each major service operation on the car, until by the time the cars are in our hands, we are basically starting from scratch.

You should have the car loaded as you would drive it most of the time, not to the maximum, unless you want it optimized for maximum loads only. (Can't resist a small plug for the Packard "Torsion Level" suspension here - which guarantees that the body is always in exactly the same position re: the wheels, regardless of load!).

From Loren:

If you don't know when your U-joints were last replaced, I suggest you spend $35.00 and get three new ones.

The back U-joint unbolts with small brackets that hold two of the caps in place. Disconnect the center drive line support and unbolt the front of the driveline ahead of the front U-joint at the back of the transmission.

I used a metal scribe to mark the connections but found the front connection to be a one way bolt pattern on my '64.

U-joints need to be pressed out after you remove the "C" clips located just at the inside face of the yokes. I used a standard "C" clamp from my wood shop to apply the pressure and two wrench sockets. One is smaller than the U-joint cap to press through the yoke. The other larger than the U-joint cap to provide a pocket for the cap to slip out of the yoke.

Use the small wrench socket and "C" clamp to press the new U-joints back into the yokes. Be careful when installing the new ones not to displace any of the needle bearings and lubricate the new U-joints before running them in the car. They are shipped packed with enough grease to preserve them but not enough to lubricate them for road use.

You may need a needle valve to install grease in the U-joints because of the restriction of the yoke. Needle valves for a standard grease gun are available at any auto parts store, as are the U-joints.

I also suggest you restore your drive line shims to the number you found in place when you first disassembled it. Without the proper tools to measure the drive line angle where it meets the differential, your best bet would be to leave it as you found it.

From Norm:

As important as the carrier height, or perhaps more so, is the phasing of the driveshaft joints in relation to one another. That means that the u joints( cv joints) should be alternated 90 degrees in order to allow them to cancel out vibrations. If you have not assembled them so that each ( front, middle, back) is at a 90 degree variation, you will get vibrations. You must always mark and observe the original assembly sequence and re-attach in exactly the same way. If you attach them that way and you still get vibration, take your driveshaft to be rebalanced because it is possible to reassemble the shaft in correct phase, but not in the same way that the factory did-and that is what the balance is based on.

Question from Don (1963):

My 64 Crown FDHT has been vibrating heavily on initial acceleration from a stop-more obvious on hard take-off. I decided to replace the driveshaft support and it's support bearing. I sent a spare to Damper Doctor and a very nice solid rubber support was returned on schedule and at the price quoted by Damper Dr. This week I installed the reconditioned driveshaft support (the one I removed from the car was literally in shreds!) with a new bearing from NAPA and 3 new U-joints, also from NAPA. When I took Nancy (64 Crown) for it's maiden voyage the vibration was much worse and for longer duration.

On the old driveshaft support once I was above a rolling speed there was no more vibration but with the new driveshaft support with bearing and U-joints up to about 35 MPH I can only feather the accelerator to in crease speed. If I try anything above a SLIGHT change of speed the whole car vibrates and resonates violently. Did I miss something or do something wrong? Is there a driveshaft alignment or installation that is unique to this style of driveshaft? Are the 2 halves of the driveshaft matched and/or balanced where they must be joined exactly so? Are the shims between the driveshaft support and the metal cross member supposed to be there with a new driveshaft support?


From Dan:

Check the engine mounts and the tranny mount.

From Kerry:

Regarding your severe vibration. While I do not know the specifics of your driveline, it could be that your "u-joints" are out of phase. Some drivelines allow you to pull the u-joint off and rotate it. U-joints should always be a 90% to each other. For instance. If the U-joint on the back of the trans is vertical, the front one on the center bearing should be horizontal and the rear vertical and the differential of course would be horizontal. Also make sure your carrier is securely bolted down. I did some work on my Chevy PU and forgot to tighten the center carrier bolts. As it started to move around, I saw the same symptoms you describe.

From PEN:

First, check your left motor mount. If that is ok, then proceed to check your rear axle control struts and bushings. If they are neither one broken, check for broken rear springs. At this age, the rear leaf springs need to be replaced anyway, and sagging springs affect driveshaft angularity. With the struts, sagging springs cause the axle to tilt upwards. Most likely is a broken control strut. But otherwise, you should be able to compensate for sagging springs by adding shims under the center hanger bearing. Chrysler had special tools to adjust driveshaft angularity, but if anyone still knows how to do that, or has the tools, they would be the ones to help you.

From Brad:

If you find sagging springs are the cause of the vibration, know that I had my '62 300 leaf springs re-arched with a new leaf added for additional support, new clamps, centering bolt and new bushings, $75.00. I didn't think that was terribly expensive to assure a level ride. It's possibly stiffer and just a tad higher than I wanted but it's difficult to predict, sometimes re-arched springs settle so I had them increase the arch by 1 inch. Of course, you may still want to go with the shims to fix sagging springs.

Follow-up from Bob:

I had exactly the same thing done to my '66 with the same results - a little higher, but maybe now settling down 1/8" a year! Great ride and "attitude" improvement. It cost me a little more (LA area) but the shop owner told me he'd install any shocks I brought in, included in the price, so for about $280 I had new shocks and much improved rear springs. The shop was Hollywood Spring & Axle.

From Dick:

I don't know what went wrong, but I think you should drive the car S L O W L Y to the nearest professional driveline service outfit, and let them straighten things out for you. The is at least one Nationwide chain out here, called "Driveline Service" who are very professional. They have bailed me out a few times. Check your Yellow Pages.

Follow-up from Don:

Someone suggested that I read the factory service manual and right there in the driveshaft section it explains how to refit the driveshaft and I did it just like the FSM says except..................there IS an alignment procedure! There is a notch on the rear shaft that is intended to match up with a "dot" on the front shaft. Once again I have learned "When all else fails-Read directions!" Thanks again to all from your assistance and looks like I'll have to pull the D/S again. Live and learn.

Follow-up from Don:

Today I removed the infamous driveshaft from my 64 Crown and aligned the keyway on the front driveshaft to the "Circle" on the yoke portion of the rear driveshaft. Took it for a ride and drove like a dream -OOPS- like an Imperial should. What a difference following directions will do! There is still a small subtle vibration/sensation on hard acceleration but I noticed the right rear axle control strut is broken and just hanging there; I guess that's next to fix! Once again thanks for all the feedback and especially for the reminder to read the FSM.

Question from Greg (1966):


Where are the shims located? On the body side or the axle? I changed rear springs and had a hard time getting the torque bars back together. Maybe they need a shim adjustment. How you set them?


Reply from Norm:


The shims are located between the chassis and the forward bracket that is attached to the chassis by 4 bolts.  The way you would adjust for angularity is by measuring the driveshaft angularity and then adjusting via the use of wedges in the springs between the spring pad on the axle and the spring itself. If the use of the wedges pushed the torque arm too far away from the chassis to connect, then you would need to shim them. NOTE: Some cars do not have either of them as the angularity is in compliance without their use. This is all explained very thoroughly in the FSM.

Question from Clay (1967):

How would I tell if I had a bad U-joint or a broken motor mount?  My '67 has a very loud clunk every time I shift it into reverse. It is always quiet though when it is shifted back into drive. The noise seems to be getting worse, to the point that I don't really want to back it up until I figure out what is wrong. I was told this could be the passenger side motor mount that has broken. Can you visually check motor mounts?


From Bob:

Sounds like a u-joint to me. Put the car up on a hoist if available and get the pressure off the wheels. Reach up and grab the driveshaft and twist from side to side. With that much noise there shouldn't be no problem seeing the bad knuckle. It will slop around and wobble. Also look for the rusty colored liquid coming from the joint. Another good indication the u-joint is shot.

From Dick:

Can you have someone shift it into reverse while you squat down alongside the car and see where the noise comes from? If it appears to come from the driveshaft, feel the driveshaft ends for side to side and up to down play when the car is in neutral, engine off. Any play over 1/16 inch means you have a bad u-joint, bearing, or spline in your driveline. Take the car to your local Driveline Service outfit, and bring money. Hope it isn't a rear bearing in the transmission, or the pinion bearing in the differential, but this is the least likely.

If all this seems OK, is your idle speed real high?  A clank from the driveline when engaging reverse is a age old MOPAR problem, the usual cure is to reduce the idle speed, if nothing is wrong with the u-joints.

Passenger side motor mounts are in compression when the engine is pulling in a forward gear, and the driver's side are being stretched. The driver's side is the one that usually fails. If you had a bad motor mount on either side, you would see the motor lift from the frame when you hold the car with the brake and run up some RPM with the car in gear. If you see the motor move more than 1/2 inch or so when you just drop it into gear at idle, I would put the car up on a lift and inspect the motor mounts for separation. I think your problem is more likely in the driveline, however.

Question from Pete (1970):

I can't go above 85 before I get a severe driveline vibration. I've replaces engine/tranny mounts and all 4 u-joints. No difference. Tried putting the driveshaft 180 degrees out-of-phase. Nadda. I think its the rear end. Its getting kind of noisy (I notice it at low speeds). I have to find a local vendor that works on sure-grip units, but no luck so far.


From Paul:

You can also have the driveshaft checked to make sure it's not bent. Other possibilities, bent rim, tire bubble (where the tread starts to separate from the carcass), and front end alignment. The rear end noise could be the outer axle bearings. Locking differentials tend to act up more when cornering than in a straight line. (In my experience, I could be wrong) There's an additive you can get for posi type rear ends. It's about a pint, I don't remember the name, but it eliminate the squawking, squealing, and horrible shrill noises that my 1976 Dodge Power Wagon was making. Your local auto parts store will have it. Just tell them you want some posi lube.

From Hubert:

I don't think that the rear end could make such vibration at 85 mph,  did you try to have the wheels balanced?

Question from Chuck (1981-1983):


I purchased "Beauty", an '81 Light Auburn Metallic Imperial a month ago and during the drive home of almost a 1000 miles, the car had a strong vibration throughout the speed range and was very noticeable at speeds of 65-75 MPH. The day after arriving home I took it to our local tire store and had all four wheels balanced. This was a definite help to my problem and around town and at speeds of 35-55 is fairly smooth. I do notice vibration, however, at speeds above 65....its noticeable in the seats and steering wheel. Could it be the drive shaft? What are the symptoms of drive shaft unbalance? What else could be affecting the ride? The tires are Goodyear Double Eagles.




From Dick:


It is very likely a bent driveshaft or worn U-joints. Either way, look in your phone book for the nearest "Driveline Services" franchisee, and let them sort it out for you.. If there is no problem with the driveline, you may have one or more out of round tires (balancing them won't help), or possibly an out of balance engine/converter. Duplicate the RPM at which the vibration occurs with the car out of gear (stopped), see if you can get the same vibration. If you do, it's an engine/converter balance problem.


One other source, if the vibration only starts after driving long enough to get the rotors hot, is grabbing disc pads. After driving a few miles, feel the wheels to see if you find one noticeably hotter than the other.


From Matt:


When you took the car to have the wheels balanced , did you have them check for belt separation on the tires? Had a friend with a a separated belt in one of the front tires and it behaved very much like you describe. Replaced the offending rubber and all was well.


From ??:


I had a rear brake shoe cause exactly this situation. They had adjusted themselves too close to the drum. I backed it off a bit and it's been fine ever since.


From Norm:


It could be the driveshaft either out of balance or out of phase. Could also be a rim(s) that has excessive run-out or is otherwise out of kilter-maybe slightly off center. Certain front end components ( tie rod ends) have the capacity to induce a vibration as well. Jack the car up and take a look at each tire as you spin it by hand: is it lumpy, does it wobble, is there a high and low contact pattern? Is one of your disc pads hanging up an rubbing against the rotor with excessive force? Rear brakes over adjusted? 


From Kne:


The vibration can be caused by the rubber inside the drive shaft coming loose. The drive shaft on the loder cars were tubes that had a rubber liner to dampen vibrations.


From John:


Could be a bad u-joint or poorly installed one. I had a 77 NYB with that problem.


From Paul:


I recently bought my '75 Newport (Feb 2001) and it had a strong pull to the right as well as a knock from the left front. I figured the knock was bearings so I bought new ones but they didn't fit and I also discovered a loose race (bad rotor). An easy fix for my rotor was to take one from my '78 Newport (derelict) which produced a HEAVY vibration above 45MPH (enough to keep me under 45). I've kept driving it this way (slowly) while making preparations to fix it (taking the spindle from the '78 and buying new ball joints) and also needing front tires. The day I decided to look at tires I got them, then discovering that I had different width rims (5 1/2 on the left, 7 on the right) which I was told could cause a pull so ........ I told them to hold off on the alignment (I decided that was part of the problem) until I could return with another 7" rim I knew I had ..................... WHAT A DIFFERENCE!!!!! Just the tires eliminated the vibration and the pull (though it still had a very slight pull) --- I got my rim, had them swap the tires (the 7" had an old one that is now on the 5 1/2 for a spare), and only needed a slight toe adjustment. Though my Newport is RWD (aren't the 80's Imps FWD?) definitely check your tires first.

This page last updated October 31, 2003.  Send us your feedback, and come join the Imperial Mailing List - Online Car Club