[edm]

Have 1993 Cab Tiptronic.

 

1) After an hour or so driving , I hear a thumping in the rear bottom , The shocks are new . Any suggestions. 

 

2) had changed the wheels from 16" to 17" , the 17" was worse as far as thumping, switch it back to 16" , only happens after an hour of driving.

 

3) HELP PLEASE....

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[ampegboy1]

Is the exhaust hitting something once it has warmed up and expanded? I recall reading about that happening to someone. It would explain why the noise takes time to start and probably why it starts around the same time each time. If it is, you may find marks on the surrounding bodywork to indicate where it's hitting. The 16" wheels would have more tyre to absorb the bumps in the road, which could explain why the noise was worse with the 17s.

 

Michael

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[MCL968]

Yes on the exhaust expansion. I had the same problem, turned out to be the Cuban food I had for lunch.

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[ds968]

That was my post on " what's that noise " -  only when the car is driven for at least 45 min to 1 hour and everything back there from wheels, to the diff , to the exhaust is really hot, I hear a rumble on sharp right hand turns and when taking off from a  stop going uphill . I thought it might have been the exhaust touching something but the consensus seems to be the wheel bearing. However, it was never a " thump ", which you're describing..     

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[RS Barn]

Track cars which turn right more often than left, always seem to have left rear wheel bearing go first. This condition can start as a rumble then progress to a thump.

I have also had CV shafts make funny noises. I've seen grease get hard and cause noise in the bearings. 

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[edm]

Thanks to all that replied, it is definitely a thump , going in a straight line, car was never on a track. I have an appointment with my mechanic in 2 weeks. Anything else i should advise him to look for?

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[94SilverCab]

Track cars which turn right more often than left, always seem to have left rear wheel bearing go first. This condition can start as a rumble then progress to a thump.

I have also had CV shafts make funny noises. I've seen grease get hard and cause noise in the bearings. 

 

Hey! Look who's back Welcome!

 

Pete and Max in the same week, be-still my heart.

 

Keep an eye on your post count, you are dangerously approaching the Magic Post 968

 

Jay

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[flash]

is the thumping rhythmic?

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[968workaholic]

Does the noise increase/ decrease with speed? How about when turning, any change from left to right? If it was worse with the 17" wheels I would lean towards a wheel bearing, but more information on conditions when is happening are needed

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[flash]

i would not assume that the wheels had anything to do with the issues.  it could easily be a coincidence.

 

again, i think the key question is if it is rhythmic or more random.  if it is not rhythmic, i would eliminate anything rotational.

 

if not rhythmic, then is it affected by throttle (i.e. on throttle / off throttle)?

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[MCL968]

Good question, Flash. I would ask how new the engine mounts are as well.

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[edm]

Sorry it took so long to reply,

 

1) the thumping noise is more audible after 45 minutes driving,seems to only happen when hitting bumps or potholes.

 

2) engine mounts are brand new, shocks are new as well ( OEM ), maybe 1 shock went bad???

 

3) Noise doesn't  increase or decrease with speed, again , only when hitting bumps or potholes.

 

4) if not rhythmic, then is it affected by throttle (i.e. on throttle / off throttle)?, ....throttle on/off not affected.

 

5) I may ask him to take down the trans to see if that is what is hitting the under side, is this a waste of time. Please advise.Thanks

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[968workaholic]

 Check that the shock mounting hardware is tight, did the noise start after the replacement?

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[edm]

first thing I checked, all good..cannot remember when this issue started.

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[az968]

You did check the trunk to make sure the spare was bolted down and the tools secured, right?

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[968workaholic]

Hmmm, sway bar end links good? How about the giant weight in the rr quarter? As mentioned above check the spare tire too if you haven't already 

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[ds968]

+ 1 on what Bob ( az ) posted , especially if it ONLY happens when you go over a bump or pothole on the road .

Oh yeah, and the rear sway bar bushings ..

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[edm]

Took everything out of the trunk ( spare tire, tools ) nothing left and still continues to happen, Thank for suggesting to check  the rear sway bar bushings . I will have my mechanic look into it. Thanks again to all that replied. I have had this beautiful car for 14 years ( 2nd owner ) and let me tell you I babied this car and would hate to part ways with it after all I put into it. It's a good thing that I have an understanding Wife. Too many memories in this car. I used this car to teach all my 3 boys to drive. That alone will prevent me from selling the car.

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[az968]

oh, yeah. way too many reasons to keep the car. just don't drive over potholes and it will be like new!

Pete (RS Barn) had a couple of good suggestions for your mechanic to also look at.  Mysterious bumps in the night are hard to trace down.

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[968workaholic]

Just make sure you drive it for 45 minutes before you get to your mechanic for them to check it out

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