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MG MGB Technical - A rhythmic, quick thumping

A rhythmic, quick thumping starts at 30 mph, continues up to 60 mph, then wind sound too loud to hear…
Sounds like from rear right section/area of auto. Brakes checked, all hoses replaced and bleed. U-joints feel good. Tires new, tracks straight, no pulling when braking; sound has been constant, although sometimes stops for a few seconds when accelerating from 40>50 on freeway; no ill effects for first 600 miles of US1 coast route trip. Motor mounts/trans mount/bushings/gaiters need replaced, dry rotted. Brake boost needs rebuild also. I’m on the road from LA to Seattle with “latest” ebay purchase (buying tools/parts as needed, along the way). Motor runs very strong and tranny works great. Advise on the possible source so I can inspect/fix…–California Dream’in LE
Joe Walck

Seems like a buy. I'm always pleased to see an MGB in use when I'm in the USA. Does this noise vary with road speed? It sounds like a tire (over there, we use tyres here) new doesnt mean good. If it follows that wheel around the car if you move it, thars a bit of a clue
Stan Best

The noise is constant, and might speed up little at higher speeds. Once in a while it stops, but only for 5 to 10 sec. I will swap from rear to front tires today. I did see that the lead weight on the left front wheel was rubbing/hitting the ball joint as the tire rotated, but that was changed/moved so as not to hit...however sound continued.
This is my 5th B, also have owned/restored 3 TD's and also have my perfect A. I enjoy buying/driving/fixing/and then passing on to the next owner, and I have owed MGs for over 45 yrs., always leaving them better than I found them, never a complaint from the buyer as I always sold for a fair price for the work and condition of the car. I usually have sold even on my investment...minus my labor...as it should be...
'79 MGB LE

Joe Walck

Last time I has something like this it was a loose Rally plaque! I wonder if its a mudflap or part of a the hood or tonneau cover flapping?
I took all the wheels off, checked to Hardy spicers etc etc. A bit embarrasing when I tracked it down
Stan Best

... every child needs one (perhaps not).

If it doesn't change with speed it can't really be anything that's rotating i.e. wheels etc.
PaulH Solihull

I suspect that it might be the transmission mounts. They have probably deteriorated to the point that the transmission is hitting the floor, while under load. RAY
rjm RAY

This thread was discussed on 29/07/2011

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