Whump!

#1
Hi, I've a 1966 2000 P6 (28k miles) and am wondering if anyone has come across this before.

If I change gear from 1st to 2nd nice and sedately all is good. No issues

If I change gear from 1st to 2nd too enthusiastically, I hear a 'whump' sound which seems to come from the rear.

It's not a bang, nor knock, nor squeal, nor whine. The closest I can come to describing it is the noise of something dropping on to your pillow

Handling is fine; car drives fine; gearbox and gear changes all good. Would like to know what this is and get it resolved. The De Dion tube will be coming off shortly to have the gaiter replaced so maybe that might shed light on issue?

Many thanks.
 

chrisw

Well-Known Member
#3
Work your way around the mounts on the back end when the de dion is out, but as has been said, the mount on the nose of the final drive is a good place to start
 
#4
Thanks both for this. If it is the mount on the nose of the final drive, is it something straightforward to remedy? Is it dangerous to leave over a long time? I've had the car a year and the noise has been there all that time
 
#5
A straight forward fix (if it was the front mount). It will making a lot more noise before any sort of big failure occurs. But it could be several things back there.

Yours
Vern
 

jp928

Well-Known Member
#6
As Vern says, it could be any or all the rear mounting rubbers. the diff nose one is pretty easy to do. there are 2 sizes of bushes listed for the diff mounting bracket, so you need to check which type you have there. on my car (suspect done 214k kms) the nearside rubber was visibly hanging lower through the body, and cracked, but the offside rubber was in very good condition. Replacing these 2 is a bit more difficult as you have to support the diff and having a helper will make doing up the mounting bolts easier. And there is the panhard rod to the body and its rubbers to check.
 
#7
Start by checking that the bolts holding the front differential mount at the end of the torque tube are all tight. There should be three sets, The main (long) bolt through the mount and tube side; The two small bolts holding the mount to the little cross member and the two bolts holding said cross member to the chassis. The Whump noise is probably due to the tube jumping up during the gear change. Gentle changing gives less of a shock loading and the tubes inertia slows its movement (so no whump).

PS the long bolt on the earlier cars dropped down from the top with nut on the bottom. This is good because if the nut comes off you don't lose the bolt....unlike later cars.
 
#8
Thanks for that Mike. If the bolts were loose might that cause some resonance in the cabin at a certain speed? Getting a bit of that on acceleration - sometimes. When cruising at 60 cabin is nice and quiet
 
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