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Thread: Thumping vibration in front end under acceleration.

  1. #1

    Thumping vibration in front end under acceleration.

    89 Spirit ES, 2.5 Turbo, 523.

    I just did a 2500 mile cross country run in my Spirit, and the car ran fine. But towards the end of the trip, I began to notice a thumping vibration in the front end, only when under acceleration, like a tire was WAY out of balance or out of round. But it feels more like it is in the drivetrain because the whole front of the car shakes a bit.

    And now that I have gotten here and the car is mostly unloaded, I drive around and notice it even more now. Under cruise and coast there is no vibration, but when accelerating it starts.

    Any idea what it might be? A CV joint binding up? The outer right joint has its boot torn up a lot and there probably isn't much grease in there. I recently dropped the transmission out to change the clutch, I wonder if I somehow reinstalled it not in the same position (passenger motor mount was never touched), and now the axles are not properly centered and one is bottoming out a bit?

    Any ideas?

  2. #2
    Supporting Member II Turbo Mopar Contributor Shadowjake's Avatar
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    Re: Thumping vibration in front end under acceleration.

    I'm 99% sure it is one of your axles. I had the same problem in my SRT4. Mine was cased by a bad wheel bearing with too much play. Inside the CV joint, one of the tripod nubs was cracked and binding under torque. Under cruise, it's fine, but when it is under pressure, it is pinching/binding as it tries to rotate.

    Just replacing the boot and regreasing the joint won't solve the problem if it is the same as mine was. You might want to just get a new/rebuilt axle. They are only like 50 bucks for the whole half shaft.
    Jake Bauer
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  3. #3
    turbo addict slasky's Avatar
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    Re: Thumping vibration in front end under acceleration.

    sounds like a bad axle
    SDAC member
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  4. #4

    Re: Thumping vibration in front end under acceleration.

    I was thinking the same thing. The vibration feels like the car is shaking side to side.

    I already know the right outer cv joint boot is torn open and that is probably the bad one. Since it is a 1 piece axle, I can go to the local junkyard and grab another one and try it out.

    I had changed the left side wheel bearing assembly to a bolt-in style a few months ago, if changing the axle doesn't fix it I can just swap in the whole bolt-in bearing assembly on the right side, or do it along with the axle job. Might as well.

  5. #5

    Re: Thumping vibration in front end under acceleration.

    I have changed the passenger side axle (one piece axle type) twice now, for good used ones a friend had laying around. And the same thing happens each time. The vibration will mostly (but not entirely) go away for a few days, then in the next few days it starts getting worse again. And after a week or 2 it is thumping as bad as it was in the first place. Only under acceleration, and the harder I accelerate, the harder it thumps. and jerks the front of the car side to side. The wheel bearings are out of a 40,000 mile Shadow 2.5 TBI, (I did a full bolt-in wheel bearing swap) so I seriously doubt they are bad. I also did an alignment on it, it doesn't pull going down the road or when braking and there is no abnormal tire wear.

    I think I should try changing the drivers side axle. I didn't think it was bad, its boots don't leak, but you never know. I have driven the car 63,000 miles, so I know it has at least that many miles on it, and probably quite a few more.

    It is possible that both of those replacement axles were bad, but I've been driving TD's for 8 years, and this is the first time I have ever seen or heard of this problem.

  6. #6
    Hybrid booster
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    Re: Thumping vibration in front end under acceleration.

    possibly bad front engine mount, take a look (check the side also if front is shot). it can be either or both the mount insert (rubber/urethane piece), or the bracket - early brackets had a weak spot near the block where they could fracture and eventually fail - later brackets had a gusset to fix this. what will happen under acceleration is the engine will shift position enough to stress the axles. if you don't catch it early enough, you can snap an axle driving on it.

  7. #7
    Visit www.boostbutton.com... Turbo Mopar Vendor ShelGame's Avatar
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    Re: Thumping vibration in front end under acceleration.

    I had a bad tie rod do something similar. Check your tie rods ends, too...

    Rob Lloyd
    '89 Daytona C/S

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  8. #8
    Supporting Member II Turbo Mopar Contributor
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    Re: Thumping vibration in front end under acceleration.

    I have had this same issue when I had mismatched CV shafts. The parts store kept getting the same style in stock which didn't match what I had on the other side. One had a stamped steel innder joint while the other was a cast iron joint; the inner boots were also different. Once I had the same style inner joint all was well with the world.

  9. #9

    Re: Thumping vibration in front end under acceleration.

    I'll look at those things. The mismatched CV joint styles never occured to me, I'll check that too. Thanks.

  10. #10
    Hybrid booster
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    Re: Thumping vibration in front end under acceleration.

    Definatly look into the Engine mounts. I had a bunch of weird noises and when I replaced all the mounts it raised the passengerside of the engine about 3/4" and the driverside about 1/4". Obviously there was some axle misalignment

  11. #11
    Hybrid booster
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    Re: Thumping vibration in front end under acceleration.

    I had a similar problem. My car was driving great, everything was how I like it. My axle boots were dieing so I swapped axles. After that a similar problem to what you described developed. After alot of messing around found that the front struts were weak (car didn't act like it had bad struts) but after replacing front struts problem went away. So wheel must have been bouncing when accelerating. For me I also had trouble if I made fast right turns...wheel would bounce.

  12. #12
    Hybrid booster
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    Re: Thumping vibration in front end under acceleration.

    My father's Daytona Z is doing the same thing, I took it for State inspection adnd on the way in i had a loud thumping noise in the front end under medium - heavy acceleration. The strange part is on the way home the noise/thumping went away and the car feels fine now, I just informed my dad of the issue and suggested an axle replacement. I suggested an axle because turning while hitting the gas seemed to make it even worse and the axles are original.

  13. #13

    Re: Thumping vibration in front end under acceleration.

    I was under the hood looking at stuff, and I noticed the pasenger side motor mount is shot. The stud has pushed through the rubber, so it has dropped down until the 2 metal parts of the mount touched. So the passenger side of the motor is definitely low. I'm looking for a good mount for it now and will change it and measure how much it raises up.

  14. #14
    Hybrid booster Turbo Mopar Contributor
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    Re: Thumping vibration in front end under acceleration.

    May sound dumb but are the lugnust torqued? I just fixed a buddy's thumb under acceleration by torquing his lug nuts. He was lucky I found it, we suspect his ex.
    KO,
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  15. #15
    Moderator Turbo Mopar Staff Vigo's Avatar
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    Re: Thumping vibration in front end under acceleration.

    Hehehe, i might be one of the few people with enough experience to discern a loose wheel from a bad axle..

    But i agree with pretty much everyone and say the problem is still coming from an axle. Now, its possible it's actually being caused by the motor being low on that side. I would replace the mount first, especially since the one on that side is like $11! And make sure not to put it in upside down!

    Dont push the red button.You hear me?

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  16. #16
    Hybrid booster
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    Re: Thumping vibration in front end under acceleration.

    Ive had a bad mount cause my axle to thump against the K-frame which caused my lug nuts to break loose. I somehow made it to work where i was able to tighten my lugs, replace the axle and engine mount. Not a fun experience but im glad i survived it so I could share it with you

  17. #17

    Re: Thumping vibration in front end under acceleration.

    I got a new mount from the local Advance Auto Parts. $12.71 including tax.

    Not only was the stud pushed through the rubber on the old mount, it seems it was UPSIDE DOWN all this time for the last 3 years from the previous owner! The solid side of the rubber was on top! I put my new mount in the same way, and was it was nearly metal on metal again and thought "that can't be right", so I took it back out, flipped it over, and raised the motor a good 1/2" at least!

    That reduced but didn't entirely eliminate the thumping.

    Tonight I took out the front mount and I have it filled with RTV now. I'll let it cure overnight and reinstall it in the morning. The stud wasn't ripped loose in the front mount, but I could flex it around with my thumb by pushing on it, so it probably flexes too much under acceleration.

    I should have gotten one of those solid adjustable TU rear transmission mounts a while back when I had the chance.

    We'll see what difference filling the front mount makes.

  18. #18
    Moderator Turbo Mopar Staff Vigo's Avatar
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    Re: Thumping vibration in front end under acceleration.

    Hooray, a statement i made was relevant!

    Glad to hear the progress, keep it up.

    Dont push the red button.You hear me?

    Got a 1.7 VW-motor 79-82 2-dr L-body for sale? Or want to trade it for one of my cars? PM me.

  19. #19

    Re: Thumping vibration in front end under acceleration.

    The RTV filled front mount didn't make any difference. Tomorrow I'm going to take off the 32mm axle nuts, put the car back on its wheels, and check to see if one axle is bottoming out. I may need to shift the engine/transmision to one side or the other. Running out of ideas here!
    Last edited by Tim; 07-07-2011 at 11:02 PM.

  20. #20
    Moderator Turbo Mopar Staff Vigo's Avatar
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    Re: Thumping vibration in front end under acceleration.

    I think you're on the right track. If that doesnt do it id be looking at another axle.

    Dont push the red button.You hear me?

    Got a 1.7 VW-motor 79-82 2-dr L-body for sale? Or want to trade it for one of my cars? PM me.

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