These days, you cannot assume anything about parts quality, because there is so much garbage on the market.
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| thump, then thunderous vibration in the rear https://slantsix.org/forum/viewtopic.php?t=25911 |
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| Author: | vames [ Mon Nov 19, 2007 4:38 am ] |
| Post subject: | thump, then thunderous vibration in the rear |
Hi. The title says it all. I was on the Taconic expressway last night in my 72 Dart. All of a sudden heard a thud in the rear of the car, then felt like I was driving on a massive rumble strip. The car was able to limp to the next exit. The rumble was really strong over about 25 mph - happens in neutral, drive, or whatever. Suspension seems to be fine. Didn't seem to be any rock or bump that I hit. I'd think it was a u-joint. I had them replaced about 1000 miles ago and maybe a defective one? But I grabbed the driveshaft and gave it some firm shaking and it didn't seem to be loose. However, it was night and I didn't get to definitively examine it. Does anybody know if these symptoms could be pointing to anything else? Failed rear end? Wheel bearings? Axle? Thanks in advance, vames |
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| Author: | slantasaurus [ Mon Nov 19, 2007 4:57 am ] |
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Have either of the rear tires been patched/plugged ??? I've had and seen tires that have had flat repairs break the belts and buldge in one or more spots. It's like driving a basketball that is being dribbled. |
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| Author: | Charrlie_S [ Mon Nov 19, 2007 5:05 am ] |
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Tires don't even have to be repaired. I have had several tires get a ply seperation. It is actually fairly common in the florida heat, if the tires don't get much milage on them. Check the tires for a bulge. |
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| Author: | vames [ Mon Nov 19, 2007 5:28 am ] |
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Thanks. I gave the tires a lquick look last night and they seemed good. The vibration is higher frequency than a tire would suggest, and not necessarily bumpy like a tire failure would suggest. It's also non-existent till I get to about 15-20 mph. That all said, I can't rule the tires out until I give it a closer look. My biggest concern right now is to see if anybody has ever had a rear-end failure occur with these symptoms. That, of course is my biggest fear. Or could something fail in the rear brake that makes it do this? The car's at a shop right now - will call them later. I usually do my own diagnosis, but it's like 50 miles away and I won't be able to make it up there till wednesday, so I might as well have the guy take a look. |
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| Author: | SlantSixDan [ Mon Nov 19, 2007 7:57 am ] |
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Two questions: 1) Were you carrying much of any load in the trunk? 2) Is the rear axle's pinion snubber plate still present? |
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| Author: | vames [ Mon Nov 19, 2007 8:30 am ] |
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1) No load in the trunk. Ride height in the back (and therefore, drive shaft angle) is quite normal. The leaf springs were replaced in the mid-1980's. There are air shocks, but very little pressure in them because the springs maintain proper ride height. 2) Have to admit I don't know what the pinion snubber plate is. It was pretty dark out there and other than the lack of apparent driveshaft play/rattle (which I can't be entirely sure of since it was in park) I didn't feel anything abnormal. Could a busted plate lead to this sort of problem? If so, is it a big fix or a small fix. Much as I hate it, I think I'm in the hands of the shop on this one. Good news is that it was a small independent shop, and when I spoke to the guy on the phone this morning, he sounded like he was in his 50's and said he's entirely comfortable with these old cars. Plus its originally from California and doesn't have any rust, so hopefully fixing one problem won't expose a bunch of major other problems. Fingers crossed, and I'll post the problem as soon as I get a diagnosis. |
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| Author: | vames [ Mon Nov 19, 2007 11:52 am ] |
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Ack. It was indeed a busted U-Joint in the driveshaft. Just spoke to the guy and he said he took care of it and will charge me $55. Not bad at all. Funny thing is that I just had the freaking mobil station around the corner from me put new u-joints in. I feel like they at least owe me an oil change or something for this trouble. -sv |
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| Author: | SlantSixDan [ Mon Nov 19, 2007 12:07 pm ] |
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These days, you cannot assume anything about parts quality, because there is so much garbage on the market.
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| Author: | dank10fenny [ Mon Nov 19, 2007 1:29 pm ] |
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i had a $#!+ ujoint fail on me, wow, what fun that is. feels like the cars about to vibrate apart. |
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| Author: | thomasj6604 [ Tue Nov 20, 2007 7:26 pm ] |
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My friend and I put both u-joints in my 1979 225 2wd pickup when we replaced the clutch about a month ago. I now have a driveshaft vibration I did not have before. The new u-joints appear centered in the yokes properly. Could the new "bolt packets" that were installed with the new u-joints throw the driveshaft balance off enough to cause a severe vibration? Also the rear tires have good tread, but are cupped and sidewall weatherchecked.Any thoughts appreciated. THANKS!! |
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| Author: | vames [ Wed Nov 21, 2007 6:35 am ] |
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Could very well be your driveshaft. Depends on the frequency and intensity.On the frequency side, an out of balance drive shaft might not vibrate enough to feel it until it hits a certain speed. With a tire, you'd probably start hearing/feeling a thud....thud......thud...... even at very low speeds. On the intensity side, since tires are on the other side of the springs and shocks from you, you'd likely hear a tire defect to a greater extent than you feel it. With a driveshaft, it's going to be like having a giant vibrator - especially because it's on your side of the springs and shocks. You can probably pull the shaft and have it balanced at a good shop for fairly cheap. You should always check your tires if you have any doubts about them anyway. |
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| Author: | vames [ Wed Nov 21, 2007 11:04 am ] |
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Also, did you bang your new u-joints in with a hammer? Could you have bent something when you did? Could you have trapped one of the pin bearings under the cap? That cap would then sit a bit off the u-joint, and that particular junction might have more friction than the others, which again could cause a vibration. Could it just be that the two parts of the shaft are now 90-degrees off from how they used to be, and a old balance job on the shaft is now out of whack? I once changed u-joints on my old cadillac and had all three of these problems. |
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| Author: | Dusty Desks [ Wed Nov 21, 2007 6:53 pm ] |
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Ditto on Vames comment about pounding u-joints in with a hammer. Anybody who doesn't have an arbor press or hydraulic press isn't equipped to replace u-joints. Our local Chrysler-Plymouth authorized service department pounded 'em in with a hammer on our '66 Chrysler, and going back for new u-joints became a sick annual ritual which only ended when my dad gave the car away to a charity for the tax deduction. |
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