Vibrating Stag - Whatcha Reckon?

[ChasR]

It is time to deal with this vibration. Whilst the Stag runs nicely and makes a lovely noise it does have one issue. Taking the car above 50MPH is near impossible with its vibrations.

I would say they probably start at around 30-35MPH from the rear when accelerating (slightly vibrating) before sounding and getting more intense at 50MPH. Pushing beyond 50MPH will result with the vibration taking over the car. To play it safe I stick below 50MPH (but of course this puts the car out of action for any long trip). Just before 50MPH arrives the diff will also whine. Once the car is warmed up it will also clonk quite a bit when going from drive into reverse or vice versa but it is fine if you go from drive to neutral to drive as well as if you perform the same procedure in reverse. A friend of mine called it the Intercity Stag LOL.

Compared a knackered inner CV on a driveshaft (I have experienced this twice on a MkIV Escort and a Mk3 Mondeo) I would say the frequency of the vibrations is quite a bit higher.

I have had the wheels checked and rebalanced, the propshaft looks to be brand new and I am told was made by a well renowned prop company near me (www.davemacprops.com). The UJs are in great conditon on the prop. It does have an aluminium toothed disc at the front (for a speedo) which is part of the front of the prop that is spigoted (however it does not come off the front of the prop). The joints also look to be in phase and as far as I can tell the rear driveshafts do not seem to be binding. Below is a link showing the disc:



One thing I will say is that the diff does leak oil via the front diff seal (in between the front nosecone and the front face of the diff), with the diff last time taking around 0.2 litres to bring it to the correct level. The car has also been converted to a ZF 4HP22 auto 'box which has been reconditioned along with the torque converter by www.drivertransmissions.co.uk . Moreover, 4 of the wheel nuts are steel with the rest being aluminium nuts (the latter are no longer available) but I was told it should not affect the vibrations. Currently each wheel has one steel nut.

I was going to take it to Vibration Free (anyone here used them?) before I start testing props and buying other drivetrain components in an effort to locate the problem but what do you think is the issue?

[Ratdat]

If each wheel has only one steel nut that wouldn't be good for balance. I'd put either all four steel nuts on one wheel or two diagonally opposite on two wheels.

[bortaf]

One steel nut wont make a vibration that bad, my cortina has those huge locking nuts with the sleave over them and a key to remove, they weigh twice what a normal nut does and I get no vibrations up to 110 (tested at brunters on a classic ford shoot).
Have you tried running the car up in air and looking for any wobbles ?, last year I had a Mk3 cortina in with similar and after running it up in the air found
A - the gearbox was not level
B - 2 of the 4 wheels wheer buckled and
C - 2 of the tyres where flat spotted from standing too long, the easy way to get rid of teh tyre issue for a while to test the rest was to over inflate them to 50 PSi to get them round again, that alowd the wheel and gearbox issue to take over and be spotted.
Obv you will have more problems with not having a solid rear axle but it need to be tested with weight on the car and teh wheels NOT drooping which may cause you a problem ? sorry not up on stag rear ends it's been a few years since I was under one

If the diff is leaking oil it's either the seal aloan or the bearing has gone and the movement is alowing the leak only way to tell is give it a dam good wiggle preferably with the prop off, as to the prop I allways thought the U/Js needed to be out of phase to stop vibrations ? but if you say he's a good propman I guess it must be right any chance of some pics we can actually see something rather than a dark who knows what? mayby up on ramps to get a decent angle shot ??

[Ratdat]

Stag is a semi trailing arm setup.

[ChasR]

I shall get some pics for Friday . The disc is a tricky thing to photo since the gearbox crossmember lives directly below it but I shall give it another go . I already tried the tyre trick (They are meant to have 25PSi in the front and 29 in the rear. I took them up to 40PSI (sidewalls say a max of 44PSI tops) with no difference.

When the prop was taken off to move the car initially the quillshaft (connects to the diff via the nosecone) had no play present. But I guess the state of the diff cannot be known from checking the quillshaft.

The other thing is that the rear has a slight amount of positive camber present with different springs fitted to the front and rear. Whether would cause a vibration issue I do not know. Whilst I wish to buy springs all round I would like to know what springs I need (when lowering a Stag, camber brackets are required to prevent the car from being lowered with negative camber being present; I suspect I may have these brackets with stock springs on the rear since it rides about 15mm higher than the front too).

I guess I had to have an awkward issue to deal with LOL.

[bortaf]

I know where your coming from mate
i know cortinas pretty well and i was at it every eve for 3 weeks, swapping parts out and road testing ect prop, wheels, tyres, bearings, discs, hubs, stub axles ect and it it turned out the "new" wheels were not actually new and all 4 had some form of buckle (2 needed 130 grams to balence ) compouned by the new tyres that were 2 years old and had been standing (show car) a lot in a garage and the box needed lowering, good luck with it all anyhoo hopefully it wont be too bad

[Dez]

have you checked gearbox tailshaft angle and diff nose angle, and how they relate to each other?

[cheggers]

WRT your leak from the diff, before you start replacing seals, make sure the breather's not blocked. It's a bit of a faff but can be done with the diff in situ - It should be on top of the diff, just to the drivers side of centre.

[andyf]

It might possibly be flat spotted tyres if it has been stood for a while?

[vitesseefi]

Ah..... vibrating Triumphs. Fought this fight a few times with Heralds and Vitesses.

Many good suggestions already. These days I tend not to mess about, but just support the rear of the car firmly on axle stands with the rear wheels well off the ground (chock the front wheels as well) and run it up to speed. With the drivetrain unloaded the vibes are usually even worse. Assuming the vibration hasn't already vanished proving the problem is at the front (never happened to me) start by taking the rear wheels off. Make a difference? No? Disconnect the driveshafts at the diff end (make sure they hang well away from the diff flanges) and try again. Still at it? Yes? It's prop-related then, which seems most likely from your description so far.

Could be:
- Simply out of balance
- Worn joint with free play
- A joint which is tight in one axis (new or old)
- Sliding spline worn out
- Sliding spline incorrectly assembled with joints out of phase (that really rattles your fillings).
- Worn bush/bearing at gearbox output end or diff input.
- UJ trunnion (at either end) flange incorrectly made with holes not concentric with spigot (I kid you not - my PI had one almost 2mm out!)
- Gearbox/diff centreline angles not correct.

FWIW, both my Herald and Vitesse have had to have their propshafts balanced on the car with jubilee clips as even new propshafts built and balanced by reputable companies (and rebalanced on one occasion) have vibrated badly when fitted. This could be a result of gearbox centreline angles being wrong though as neither had standard gearbox installs.

In your case I'd add that speedo trigger wheel to the suspect list. If the two sides are not machined concentric that'll cause shake....

Good luck

Nick

[RetroWarwicK]

were the wheels "dynamically" balanced which runs the wheel/tyre up to motorway speed? most tyre places use ones that spin up to about 20-30mph

Warringtons in warwick have a dynamic balancer

based on what vitesseefi said, I reckon it is the prop and the prop/diff angles because the you've only just had the box back in. its all been disturbed and new props don't mean they are perfectly balanced. I'd chedk those components before looks at other stuff which in theory should not have altered.

[ChasR]

I did consider the balancing aspect but both of my Pugs come with centreless wheels (as most GTi owners know they are meant to be notoriously hard to balance), both of which are balanced very well (so much that the cars drove vastly different when they went onto new tyres). I guess the car may have slipped the net.

Bar Vibration Free in Oxford, does anyone know of any other prop balancing firms in Warwickshire bar Dave Mac Props? The prop angle shall be getting checked out tomorrow. Would the rear wheels being on a positive camber throw out the UJs (but then again a number of Stags/2000/2500s run negative with lowered springs with the same suspension setup....).

[bortaf]

Dec 4, 2011 0:23:59 GMT ChasR said:

I did consider the balancing aspect but both of my Pugs come with centreless wheels (as most GTi owners know they are meant to be notoriously hard to balance), both of which are balanced very well (so much that the cars drove vastly different when they went onto new tyres). I guess the car may have slipped the net.

Bar Vibration Free in Oxford, does anyone know of any other prop balancing firms in Warwickshire bar Dave Mac Props? The prop angle shall be getting checked out tomorrow. Would the rear wheels being on a positive camber throw out the UJs (but then again a number of Stags/2000/2500s run negative with lowered springs with the same suspension setup....).

the 1.6 pug wheelasaint had to balence you just need a hub converter for the machine and bolt em on like you do on a car, if the tyre shop don't have one go elsewhere

I don't know wnough about stags to comment on the rear set up but certain angles are worse cos as the car accelorates and the rear angles change some go further into the "non wobble or safe zone" where as if your already out the other side of that zone it only gets worse

[ChasR]

I have been checking a couple of things out today .

The flange angles are a little different to the 'box and diff. But then the engine is at the right angle (Stag engines came with a 7 degree tilt going backwards from the factory) so surely that must have been an issue with a stock gearbox too. I guess I shall have to investigate that aspect.

After checking the driveline play alot of the play is in the diff... It seems to develop more play once the car has warmed up too :S.

[les509]

Do you have positive camber on the rear because the sliding splines are seized on the driveshafts? Have had that before on Triumph 2000s - obv same set up as your Stag

[ChasR]

I can bounce the rear of the car up and down and as far as I can tell the camber does change on the wheel to become positive. On the road it does not seem to suffer from the 'Stag twitch' either.

However the diff nose and gearbox output shaft angles do not line up so I shall be trying to rectify that first.

[Kyle67]

Only 2 things I can add, a twisted tyre or the diff. One of my old Triumphs used to do the same, whined like hell and nasty vibration until one day it spat it's diff. Replaced it with a secondhand one and everything was cured.

[ChasR]

A small update here.

Since last time, I identified a slight amount of play in the output/gearbox flange after a specialist took a look at it (I plan to tighten that), and I changed a few things:

• Gearbox crossmember bushes (they were missing/distorted)
  
• Gearbox mounts (they had be bodged into place and went soft/distorted)
  
• New gearbox bracket made up (as said, the mounting bushes were simply drilled into the crossmember last time and forced to bend in wierd ways)
  
• New wheels with correct diameter tyres (205/60R15 vs. 185/70R14 (Originals were 185R14).
  

And the result....

It still vibrates. It is now however near enough a smooth and serene experience up to 55-60MPH (smoother than before), making the car more usable. Whilst it still vibrates, it may be less, and you can still hear the drumming/vibrating sound.

The other day, Rob (Hoopsontoast) and I took the gear selector off from inside so we could see the gearbox and front of the propshaft. The propshaft was not vibrating at all and nor was the gearbox wobbling about (bar when the car went over bumps).

One thing we did notice was that the trigger wheel was causing the propshaft to run 1/2-1mm out of true. I did try to remove this trigger wheel from the prop before but it appears to have been forced on (I shall have to drop the exhaust and put a hub puller onto it) Whilst I can appreciate it would cause a vibration surely it would not cause the severe drumming vibration from the rear of the car to eventually take over the entire car.

Whilst I want to get the prop balanced I can appreciate it is not a cheap exercise and the fact that my prop looks near enough brand new with perfect UJs.

I do love cars sometimes...

[andyborris]

Here's a little one, try using the steel wheel nuts to locate the wheel on the hub. The sleeve nuts aren't very good at getting the wheel "central" on the hub, do each wheel in turn.

Unless you've swapped to steel nuts all round!

[ChasR]

The new wheels take different nuts (radius nuts).

However, my dad was following me today and reckons that the left wheel was shimmying slightly. I know after doing some research on the car that my car had a wheel fall off it on the left hand side due to the wheel nuts being inadequately tightened by a previous owner. Whether it may have bent the hub is worrying me (they are crazy money for a hub ).

Someone did say to try putting the handbrake up gently when the vibration occurs. There was no vibration present.

For those wanting the rear suspension layout, this should give you a good idea






The diff backplate forms part of the rear subframe as does the diff.