Propshaft Balancing

[Ian Vincent]

My TR3a is pretty smooth up to about 60 mph but above that it becomes a bit rough which becomes annoying.  It doesn't appear to be engine related because the engine will cheerfully rev up to 4500 and beyond without exhibiting any distress and anyway when I rebuilt it a couple of years ago I had all the rotating parts along with the clutch and flywheel assembly balanced by a reputable engineering shop.  I also don't think its the wheels as they have been balanced.

The only thing I can think of is the propshaft.  Although the UJs are good, (I replaced them when I rebuilt the car), and the arrows on the sliding joint are properly lined up, I have no way of checking if the thing is properly balanced.

What is the collective wisdom of the forum on the need to balance the propshaft and to what extent might that be where my vibration/roughness is coming from?  Any other suggestions gratefully received.

Oh - and if I just went down the simple route of buying a new propshaft from Moss (current cost circa £180) does that come fully balanced?

Rgds Ian

Edited January 12, 2023 by Ian Vincent

[stuart]

Proptech make really good props with much uprated Hardy spicers and are what I fit. https://gb.kompass.com/c/proptech-ltd/gb82467406/

They dont have a website so talk to them direct.

Stuart.

[Kevo_6]

+1 for Proptech. I had my prop shaft reconditioned and balanced plus I bought their uprated driveshafts. Totally recommend them.

[keith1948]

Hi Ian

Take your old pro-shaft to Proptech and they will take a quick look at it and tell you if it can be balanced or not. I have done that and they said it was too worn so a new one was required. Didn't have the funds at the time though for a new one so put old one back on the car. I did fit their uprated drive shafts though and they were excellent.

Keith

[Richardtr3a]

I had my propshaft balanced by Propshaft service in Feltham  . They eliminated the vibration and they finished the job while I went to Moss and back., where I bought a new nut and bolt set. This helps with the balancing and is safer than using the old bolts again. This kept the petrol costs in control.

It is a great answer to an irritating problem

Richard & B

[Charlie D]

1 hour ago, Ian Vincent said:

...I also don't think its the wheels as they have been balanced...

Ian,

Having suffered from vibration problems myself I have spent ages looking through old threads and it seems to be a VERY common problem, almost always around the 60 MPH mark.

There also seem to be 101 possible causes/fixes.

Bob has mentioned he had success by balancing his rear drums. (Something most people would probably never think of.)

I also thought that the problem could not be due to wheel balance, because I had four new tyres fitted and had the wheels balanced by a local reputable tyre firm.

When I made myself a wheel balancer I checked my supposed balanced wheels and found them all to be out. Using my crude machine I rebalanced and, while the result was not 100% perfect, it did make a vast amount of difference.

Maybe worth taking your wheels to a different tyre fitter and see what they think.

Charlie

[Andy Moltu]

Dave Mac in Coventry are also a good option for propshaft balancing/ replacement.

I was also shocked how much vibration shedding a balance weight off a rear wheel made. Not the first thing you check after less than 1000 miles on new tyres that had been balanced at fitting.

[Nigel Triumph]

5 minutes ago, Andy Moltu said:

Dave Mac in Coventry are also a good option for propshaft balancing/ replacement.

+1

I've also used Dave Mac, and am completely satisfied with the new prop they made for my Scimitar.

Nigel

[Ian Vincent]

Thks all, plenty to think about there. 

Rgds Ian

[John Morrison]

Ian, 

get up to your optimum vibration speed and on a clear road knock the car into neutral,

if the vibration goes or changes, then suspect the prop, if not them suspect something rotating.

John

[Lebro]

But the prop will still be rotating in neutral !

Bob

[John Morrison]

But not driven 

John

[Z320]

I’m with Bob, rotating (and driven by the rear axle)

Edited January 13, 2023 by Z320

[Charlie D]

As I mentioned earlier, this is a problem which seems to crop up quite often, but there never seems to be a decisive answer.

I have to admit that, to a certain extent, I’m with John.
Yes, the propshaft is drive even when in neutral, but as Marco says, this time it is driven by the rear axle, not by the engine. I have a feeling that that fact could well alter the “Vibration-ness” of the propshaft.

How and why, I don’t know. Play that only manifests itself when driven by the engine end? Maybe. But the fact it is driven from a different end could possibly make a noticable difference.

Charlie

[John Morrison]

Done this more than once, 'To prove a point'

Many years ago I worked for Michelin as a sales rep, but with an interest in teh technical side if things.

It was often the case that if a vehicle had a problem, easiest thing to do was blame the tyres, 'They do that sometimes sir' said the dealer!

The only way often to refute this was to show the customer the actual problem - hence getting involved.

Driving a rear wheel drive car up to a speed that induced vibration, and then putting the car into neutral, often proved the point that the issue was drivetrain.

From Ians point what has he got to lose? this is simple and free. Simply removing the propshaft and taking it somewhere will I'm sure get it rebalanced at a cost of time and dosh.

On a mates car, even before my Michelin days, we once solved vibration on a pals car with two Jubilee clips, mounted opposite each other, and by trial and error, one fixed we moved the other in relation to the first to make the balance acceptable - happy days playing with old cars, - and they still are!

John.

[Bfg]

51 minutes ago, Charlie D said:

As I mentioned earlier, this is a problem which seems to crop up quite often, but there never seems to be a decisive answer.

I have to admit that, to a certain extent, I’m with John.
Yes, the propshaft is drive even when in neutral, but as Marco says, this time it is driven by the rear axle, not by the engine. I have a feeling that that fact could well alter the “Vibration-ness” of the propshaft.

How and why, I don’t know. Play that only manifests itself when driven by the engine end? Maybe. But the fact it is driven from a different end could possibly make a noticable difference.

Charlie

Correct..

Driven from the engine - gearbox the drive / prop shaft is under load and twisting, so any out of alignment (due to play or poor location of the UJ bearings) would manifest.  Whereas when the shaft is driven from the diff, when in neutral or clutch disengaged - the gearbox end is free wheeling and so the torque to induce twisting is not there.  Coasting in gear would induce reverse torque in the shaft.

Pete

[boxofbits]

1 hour ago, John Morrison said:

Done this more than once, 'To prove a point'

Many years ago I worked for Michelin as a sales rep, but with an interest in teh technical side if things.

It was often the case that if a vehicle had a problem, easiest thing to do was blame the tyres, 'They do that sometimes sir' said the dealer!

The only way often to refute this was to show the customer the actual problem - hence getting involved.

Driving a rear wheel drive car up to a speed that induced vibration, and then putting the car into neutral, often proved the point that the issue was drivetrain.

From Ians point what has he got to lose? this is simple and free. Simply removing the propshaft and taking it somewhere will I'm sure get it rebalanced at a cost of time and dosh.

On a mates car, even before my Michelin days, we once solved vibration on a pals car with two Jubilee clips, mounted opposite each other, and by trial and error, one fixed we moved the other in relation to the first to make the balance acceptable - happy days playing with old cars, - and they still are!

John.

I get you’re meaning, but it would not necessarily be the propshaft, and by putting two opposing weights randomly in place at opposite ends might mean that by adjusting the position of the second clip you are only partially balancing out the unbalancing effect of the first.

Also the propshaft is probably the most perceptible part of the drivetrain being so long and lanky to ‘feel’ vibration, and could act as an amplifier for a much more ‘indiscernible’ or visually obscured vibration such as the start of a break-up or wear in a gearbox, main-shaft or differential bearing. So it is conceivable that you could ‘balance out’ a vibration which belongs to another failing component.

Why would you assume that a propshaft that has delivered say 80,000 miles of trouble free motoring would suddenly start to vibrate, assuming of course that the joints were intact and the original balance weight was in place? So why would the answer be to hang weights on it?

[Z320]

Hi John,

reading all this again I‘m still with Bob.

But I‘m also with you! The issue has 3 aspects.

Ian should do the test you advised him and reported here.

Ciao, Marco 

 

 

Edited January 14, 2023 by Z320

[Ian Vincent]

Once we get a day when it isn’t pouring with rain I will be doing John‘s test and reporting back. 

Rgds Ian

[barkerwilliams]

I have had very good experience of propshaft repairs and balance  in Bristol,

https://h-j-chard-engineering.business.site/

Alan

[Ian Vincent]

16 hours ago, barkerwilliams said:

I have had very good experience of propshaft repairs and balance  in Bristol,

https://h-j-chard-engineering.business.site/

Alan

Hi Alan and thks for the suggestion. I did look at this company but of the 9 reviews they have on Google, four say don’t touch them with a barge pole and four say they are excellent with  the odd one out giving them only three stars. So on that basis I sought the collective wisdom of the forum. 

I was planning to do the JM test this morning but last night on the way back from a night out I saw that the gritting lorries were out spreading so I’ll give it a miss for now. I don’t mind rain but see no need to drench the car in salt if I don’t have to.

Rgds Ian

[Z320]

Hi Ian,

rainy and windy weather here, time for a post.

You wrote your u joints are good and you suppose your propshaft is bad balanced, based on this I'm with Bob for case #1:

Your poor balanced probshaft is fast spinning (under load), you have vibrations and act like John suggested.

Nock in neutral, probshaft is still fast spinning (without load) and you still have the vibrations because it is poor balanced.

You give it to a workshop and he balances it fast spinning and without laod. Like on the car with the gb knocked in N.

Problem solved.

Based on own experience I'm also with John, supposing your u joints are indeed sligntly worn for case #2:

The yokes on our TRs are both angled and even a slighty worn u joint is causing vibrations, more under more load.

The joint is buckeling (correct engl. terminus?) over a mechanic resistance back and forth.

You act like John suggested and nock in neutral, the vibrations disappear = u joint worn.

This problem you can't balanced and you even don't notice this by balancing, because a propshaft ist balanced

with the u joints straight (not angled, not moving at all) AND not under load.

Case #3 is the not homogeneos movement of angled u joints. This can be set to neutral by 4 measures:

- forks of the propshaft in the same orientation

- both u joints angled the same ammount, the gb / diff shaft in Z orientation (TR4A-6) or W orientation (solid axle)

- difference of angle less than 0.25° (from a technical dokumentation of a propshaft producer)

- angle the probshaft less to gb AND diff (you can't change his on your TR)

BUT most importend: as also stated above it can be also something different!

Ciao, Marco

Edited January 15, 2023 by Z320

[Richardtr3a]

That is a very good answer. Well done Marco 

[Andy Moltu]

In my experience propshaft  balancers will want to replace the UJs as part of the process. No point doing the job with a worn or failing joint.

[Z320]

Sadly he did in my case because it was really only slightly worn…

The issue was to make a new one from a MX5 (gb end) and TR (diff end) propshaft, both already used.

To order a new one from Dave Mac (highly recommended) is expensive in these post Brexit days....

Edited January 19, 2023 by Z320
Post, not pre