prop shaft out of balance - uni joints tired?

bandito

bandito

New Member
Hello,

the cause of the drone, the resonance at about 45 Mph,
is an unbalanced prop shaft, says another mechanic.

What is the cure for that?
Is it advisable to buy a used shaft and universal joints?
Which new universal joints will fit?

Can the prop shaft be balanced, i.e. like a wheel, by applying weights?

Sigh. ???
 
Bandito,
if the propshaft has been un-coupled at some time it may have been put back 180° out.
Try unbolting , turning it 180° and retightening bolts.
I hope this is the answer as it's easy to accomplish and for no outlay.
This is what harveyp6 means I presume.
Regards, John.
 
No that's not what I mean, the sliding joint needs to be assembled in the correct position. On the front and rear sections are arrow markings that need to be in alignment. Pairs of joints need to be "in phase" for the wont of a better expression.
 
You can have prop shafts balanced, the usually spot weld small weight plates to the sides to balance them, you should find your shaft has one attached somewhere.

Its quite common to have a shaft shortened / lenghtened for custom installs etc.. usually requiring a re-balance.

Have a look in the yellow pages for a prop shaft specialist, they do exist !
 
After the prop shaft has been balanced and properly installed, and the drone still exists, will you be able to find that mechanic?

Dick West
 
Good point! I noticed he didn't offer to get the problem sorted, just, that's what it is mate, now off you go! That's what I call REAL confidence in your diagnosis! :D
 
Hmm.

An unbalanced propshaft is seriously unlikely unless there has been a very specific event to cause it. The most obvious is grounding the car on something solid VERY HEAVILY. Getting the propshafty alignment wrong requires first that you take the prop off and then dismantle the spline joint. Both are unlikely to occour unless there is some other major problem. I presume you'd know about these if they happened during your ownership.

Has the drone started recently or has it been there since you've hasd the car? (if the latter then we can't rule out the mis - assembly or bad thump theories - but they are still unlikely!)

Most likely propshaft induced drone would be UJ's defective - they don't have to be loose, they can be dry seized as well. Replacement UJ's come up regularely on e bay for not a lot of money. Get your tame mechanic to fit them as penance!

On the same theme you need to check all other road speed related issues. First off, gearbox tailshaft bearing - unlikely to survive long without progressing to puddle of oil stage. Then there are the half shaft uj's, wheel bearings and perhaps something in the diff.

If you need hints on how to check these and what sort of noises they make then post again and this can be expanded.

MIght help as well if you can describe your drone a little more specifically (mmm opportunities for a really silly post here I think).

Best of luck

Chris
 
Ok Chris,

You started this. The drone is not at all existing up to about 37 Mph.
Then a rumble sets in. When the rear view mirror was not as tight as it is now,
the picture got all blurry and torn out from top right to bottom left.
Closer to 45 mph, the mirror started to rotate and the drone is full on.
If you were going down hill and pop the clutch now, she really takes off
and the gas pedal starts to wave at you from the bottom right, ah well , you know where the blimming gas pedal is. Going through 55 mph the car calms down
i.e.the amplitude of the resonance sort of diminshes.
It sounds roughly like this:

mmmooooohhrruddududdududuuduuududududuuuuuuurrrmmmbaaaaahhhmoejh..

other observations by previous mechanics:
after test driving in town, under 45mph
what does he want? all is ok! Had her on the ramp, moved all the bits and found no excessive play" 35£ down the hatch.

another: I don't know, mate, seems ok to me!

the latest:
gearbox end bearing has slight play, no wonder with that violent shake!
shouldn't drive, really. UJs and propshaft want replacing.
Don't bother with second hand parts, you want want to keep her, don't you?

He is going to inquire and will come up with a price tomorrow.
On top, the water pump and the clutch slave cylinder had it.
Where does it all end?

How much are new UJ and a propshaft?

Thanks for your kind words!
One day, all will be good! :cool:
 
Hi bandito,very brave of you to attempt to describe a noise/drone over cyberspace, full marks for trying!
Personally I would suggest forget using an ordinary garage. Put your efforts into finding someone who has P6 experience, and preferrably a lot of it! The ordinary run-of-the-mill mechanic just won't know what he's looking for. All they will do is guess and charge you for the privelidge!
I would also approach the problem from a slightly different angle. Find as many things that are faulty and so therefore need replacement anyway, and work your way thru them and see what makes an improvement.If things don't help, at least they needed replacing anyway.
Thats where the P6 experience comes in,they should know where to look and what to look for.
trying to diagnose things on the forum is OK, but there's no substitute for having the car in front of you.
Keep trying and you'll get there in the end!
 
hi bandito,
i should have a look at your rubber bushes on your gearbox mounting, if they are split/perished etc that will cause vibration.

ianp6man
 
sounds like the rear hub bearing has a flat spot,i've found that after a car has been stood idle for any length of time (usually sat in a garage for a couple of years)the bearing outer race develops small ridges,...hermione had been parked in a garage for 11 years, one owner 34000 mls,about 2 months after i bought her a similar noise you describe appeared,( i thought it might be a U/J,) turned out to be N/S/R hub bearing......replaced the bearing and the noise vanished: :)
 
What.
just replacing rear wheel bearings cured the drone?

My car (un-named so far, will wait until the kids are back from hols)
has been laid up for 18 years, so that may well be similar.

Thanks!
Bernd.
 
Yeah, don't discount the rear wheel bearings. Our Mk2 Escort was one owner from new, genuine 39,000 miles when we got it. One of the rear wheel bearings had failed due to the car being sat in a carport for 4 years! :D
 
easy way to check it, ... chock the front wheels (made mine from old offcuts of railway sleepers),jack up one side using the lower link arm,(release handbrake transmission in neutral,).....now the naughty bit, you need a second operator to sit in car,start engine and put it into 2nd gear or drive for auto's,the wheel that is off the ground will start to turn,(dont rev the engine use idle),any bearing roughness will show itself as a high pitched whirring noise,repeat this procedure with the opposite side.....18years you say ???,think that i would look at replacing all wheel bearings,...grease cant be up to much !!! :p
 
HI Bandito

Sorry to have started you on this and then not replied - I've been away for a few days.

Wow, that rumble sounds spectacular! I had concerns that it was going to be neareer to a drone or a vibration - you can never tell usually until you hear it yourself - peoples perceptions and descriptions vary so much.

First comment is that it definitely sounds prop shaft or immediate vicinity. BUT if the car has been off the road stood for 18 years there are a raft of things I would change as a matter of course. Prop shaft UJ's would be amongst these! So would all wheel bearings!

I don't want to sound prescriptive or discouraging, but I would regard initial forrays as an opportunity to understand what's wrong with the car(!).

I'd of course be changing the tyres (just the age related deterioration of the rubber is enough to reder them dangerously susceptible to sidewall explosion). That might help here as a reallt big flat spot or distortion in a tyre could sound approaching this.

I'd also want to renew all rubber in the braking system, ie master cylinder seals, servo seals, all caliper seals and the flexible hoses as well as the brake fluid (bound to have swallowed a lot of water so now prone to boiling under severe load).

Then theres all the UJ's (incl the half shafts) and wheel bearings.

I'd also be keen to have changed oil seals with exposure to the outside world eg diff output and input shafts seals and the gearbox tailshaft seal. Then there'd be things like the fan belt and the water pump.

sorry if that's daunting but I'd regard all those as consummables in this context!

We've done all this work on my NADA import that's being reconstructed for Thailand and it is astonishing the internal state of things like the wheel bearings and the uj's once removed which showed no obvious external distress!

If after the tyres, uj's and wheel bearings the problem persists (and I'm 95% sure it won't) then my next port of call would be to ring up one of the specialist such as Red Rovers or Joseph Wilson's for a replacement prop from a scrap car.

Hope that helps

Chris
 
Hi, no one has mentioned the harmonic damper fitted to the casing extension to the rear differential.

Is this in position and are the rubber bushes in a sound condition?

I have never driven a car where this has been missing, so I do not know what it would sound like, but it was installed to damp out the drone of the mechanical noise to the rear differential. But if the harmonic damper was missing it would not look obvious that it was so, i.e. no broken fixings, rustly holes and the like!

Anyway, check that it is still there and if it was missing I would imagine that its reinstatement would affect only the sound not the vibration, which must be something else, like those items everyone has previously mentioned.

Good luck.

Gary
 
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