Chasing down a small high speed vibration

[MLCstag]

Hi all,

I'm trying to track down too small issues that may or may not be related. I first noticed it on a trip to Switzerland last year when doing >65mph. A relatively small vibration could be felt throughout the Stag coming from the floor. The vibration appeared more pronounced when decelerating or at constant speed as powering through 65mph it is generally better.

Later in the same trip I started to hear a 'thump, thump' sound again only very quietly, maybe two times a second at about 40mph. This could have been there all along or it may have been new.

Just been on another trip to the South West from Chester and the vibration is still there so driving tends to be at 65 max, except when occasionally overtaking. I would now like to track down the offending fault and look forward to some higher speed causing.

To start, I've been under the car and checked for play on the prop shaft to quill shaft joint and all feels ok. The drive shafts however have play and my lack of experience cannot decide if this is 'normal backlash' or a fault as both are similar. I do however suspect they are not in good shape. The movement in the driveshaft is difficult to locate and it looks like either the sliding joint (i.e. splines worn?) or the inner UJ. There may also be some tiny movement in the axel inner shaft but my eyes are getting too old to see that clearly.

I have a short video clip (if it uploads) that kind of portrays the play in the driveshaft as a sound. Any thoughts please on the likely cause of the vibrations and the play in the driveshafts.

https://youtu.be/cN3Fdr7-Wmg

Many thanks
Brian

[Paul Roberts]

I suspect the UJ's are slightly worn and possibly dry.

[milothedog]

Hi all,

I'm trying to track down too small issues that may or may not be related. I first noticed it on a trip to Switzerland last year when doing >65mph. A relatively small vibration could be felt throughout the Stag coming from the floor. The vibration appeared more pronounced when decelerating or at constant speed as powering through 65mph it is generally better.

Later in the same trip I started to hear a 'thump, thump' sound again only very quietly, maybe two times a second at about 40mph. This could have been there all along or it may have been new.

Just been on another trip to the South West from Chester and the vibration is still there so driving tends to be at 65 max, except when occasionally overtaking. I would now like to track down the offending fault and look forward to some higher speed causing.

To start, I've been under the car and checked for play on the prop shaft to quill shaft joint and all feels ok. The drive shafts however have play and my lack of experience cannot decide if this is 'normal backlash' or a fault as both are similar. I do however suspect they are not in good shape. The movement in the driveshaft is difficult to locate and it looks like either the sliding joint (i.e. splines worn?) or the inner UJ. There may also be some tiny movement in the axel inner shaft but my eyes are getting too old to see that clearly.

I have a short video clip (if it uploads) that kind of portrays the play in the driveshaft as a sound. Any thoughts please on the likely cause of the vibrations and the play in the driveshafts.

https://youtu.be/cN3Fdr7-Wmg

Many thanks
Brian

You have something very wrong there Brian, you should not have movement that makes such noises? Disconnect each shaft at the diff output flanges and see if you can isolate the cause of movement and noise.

Ian..

[MLCstag]

Thanks Paul/Ian I'll start dismantling at the diff end and take it from there. I take it the drive shafts should have no discernible movement then?

[milothedog]

Thanks Paul/Ian I'll start dismantling at the diff end and take it from there.

I take it the drive shafts should have no discernible movement then?

Correct, you may have some play / lash (A small amount) in the diff but the shaft Uj's and splines shouldn't

[MLCstag]

Ian, drive shafts disconnected from diff and found all the play is in the splines, guess they are US and I need replacements?

Whats the thoughts on refurbished driveshafts, aren't they likely to have worn splines too. My Stag has only covered 43000 and they are probably deceased! Do you think this wear would cause a vibration? Sorry for the barrage of questions.

Brian

[milothedog]

Ian, drive shafts disconnected from diff and found all the play is in the splines, guess they are US and I need replacements?

Whats the thoughts on refurbished driveshafts, aren't they likely to have worn splines too. My Stag has only covered 43000 and they are probably deceased! Do you think this wear would cause a vibration? Sorry for the barrage of questions.

Brian

It's catch 22 really Brian. they are worn so could be the cause but until you replace them you won't know if they were the problem or it's something else

If you have the shafts with circlip UJ's then Paddocks will sell you just the 2 sliding parts. (£85 + Vat each) and if you have them apart you best to fit new UJ's. So your looking at about £250 for parts. This is assuming your rear wheel bearings are still OK. If not your aswell to fit complete reconditioned shafts (Best part of £400 a pair ) but then again if you have Peened UJ's you'll probably have to do that anyway.

Or if your feeling really flushed there are always the CV type at a grand a pair

Ian.

Ian.

[Andrew S]

If you have a really good friend, he will swap his over for yours so you can test and then you will know and if the same, grease up the splines and put up with any play. The main point is eliminate the vibration. It doesn't take long to swap them over

[MLCstag]

If you have a really good friend, he will swap his over for yours so you can test and then you will know and if the same, grease up the splines and put up with any play. The main point is eliminate the vibration. It doesn't take long to swap them over

Like the idea Andrew. Anyone near Chester got a spare pair I may borrow?