Hub carrier vibration - please help!!!

[makepeace]

I have been trying to track down a vibration in the rear that starts at about 70 km/h. The previous owner mentioned that there was a vibration that fits the description which started after he had the propshaft UJs replaced.

Today, I thought I would start there and try and do a DIY balance of the propshaft (hose clamp method), but after getting the car jacked up, wheels off and running up to the vibration speed, I didn't find any issues with the propshaft at all!

I jacked the car underneath the hub carriers to ensure the correct driveline.

What I did find was that the hub carriers are rocking in and out on their axle. Looking at the driveshafts, it seems like the inboard side is fine - at the brake drums I can't really see any deflection, but if I look at the hub carrier side there is serious deflection, which matches what I think I feel on the road perfectly. It seems to be both sides, but the right is far worse.

Please see the video below - hope it's clear.

https://youtu.be/PgpInx-amTY

A photo of the rear just in case anything jumps out.

Could this just be worn UJs or does it look like something more untoward like bent driveshafts or suspension components? Where should I start with this? Appreciate any thoughts.

Edited January 15, 2022 by makepeace

[Straker]

If you’ve still got the elite up on jacks I’d recommend repeating the test with some white dots on the shaft, UJ & hub, hub carrier which will help highlight the source.

whilst you’ve got it up on jacks it’s worth fabricating a dif brace from some U shaped steel channel.

Edited January 15, 2022 by Straker
Poor spelling!

[EXCEL V8]

I'd probably start by swapping the driveshafts over to see if the oscillation follows the drive shaft.  While the drive shafts are off you can check that the u/js are correctly spaced within the yokes - make sure all the circlips are there!  If the "centres" are still clean at each end of the main drive shaft you could get someone to run them up on a lathe between centres to see how straight they look.  The inboard end looks quite stable in its rotation.

Pete

[makepeace]

Thanks for the suggestions all. I can't understand how it could be a bent driveshaft - seems a bit extreme. Will follow the route of swapping things around and noting differences. Also want to try and rotate the hub yoke and see if that does anything. I'll also replace the UJs and wheel bearings while I'm fiddling around with this issue.

I have a question on the hub bearing arrangement which I will ask in the other thread.

[black eclat]

Also check for excessive endfloat on the diff output shafts.

[Dunc]

I've got this on mine Michael - sounds like you may have prior experience?

What is the cause? Is it the output shaft bearing that fails causing the movement? I see Mike and Co at Lotusbits offering new output shafts with the bearing pressed on, which looks like a whole lot more fun than swapping out my diff.

I was between London and Edinburgh and thought it was a failing UJ and limped in at 3am. Inspection showed the driveshaft was fine but the pass side diff stud had snapped, which I think allowed the suspension to act as a slide hammer on the side of the diff for 100 or so miles. I cut the seized stud out with a recip hacksaw. I've put it all back together, but now have waaaay to much in and out play on the passenger side output shaft, and an interesting noise when I turn right.

what's the likely cause?

[EXCEL V8]

There should be no axial movement of the diff output shaft.  The bearing is held in place in the diff casing by shimming the flange to get the correct nip.  However, if the bearing is failing there may well be some axial movement.

Pete

[Dunc]

Thanks Pete - something is not right as I have about half an inch of in and out play. I have another diff kindly donated by Roddy M, but obviously fitting is a pain. Swapping a new shaft in is probably worth trying before I pull the entire back end of the car off to swap the diff out.

[EXCEL V8]

If you have that kind of movement something has gone seriously wrong - the diff will be full of all kinds or debris.  I'd bite the bullet rather than letting it eat itself.

Pete

[Dunc]

Yes, If I elect to at least try swapping an output shaft, I will pop the rear cover off and clean it all out to see if there is any swarf. I probably will end up fitting a new diff as its a 4.1:1 so the legs are a bit short for 8 cylinders, but I know I will have to cut out the stud on the drivers side and that it will fight me every step of the way.

[EXCEL V8]

JB Sports Engineering - the Morgan specialists - have all sorts of ratios available for the HA7.  £1400 per set.

Pete

[Dunc]

LOL - they do.....

Billy also has one of my diffs that he was supposed to build with an LSD and a fancy ratio... After phoning him every month for a year and a half to check on progress - I gave up, figuring if he has progressed it, he will call me.

Never heard from him again.

[makepeace]

Hi Pete, I posted a question in the bearing thread on the whether the hub should be clamped to the stub axle via the bearing arrangement, rather than floating on the splines. Would appreciate if you could have a look? 

 

 

[EXCEL V8]

Hi Jono - sorry, I saw that and meant to reply! 🙄 - brain the size of an ant theses days!  The hub doesn't float on the splines - it's pulled up hard against the bearing inner race.  In fact it's this that keeps the bearing in one piece - otherwise the two halves would wander apart (it's effectively two angular contact bearings in one outer race).  If your hub is loose then the bearing halves are as well.  I have seen in the past - probably poor assembly - where the inner face of the hub has disintegrated just behind the oil seal.  If that has happened to yours that would also account for why your outer drive shaft is wobbling - the two parts of the bearing have moved apart.

Pete

[makepeace]

Hooray! Thanks for that Pete - that seems to be the problem then! Would make a lot of sense. And I'm a little bit terrified now that I took a 1 hr drive on the weekend!

So in terms of the disintegration of the hub, what I am looking for is that the inner boss of the hub (face perpendicular to the stub axle) contacts and squeezes the inner bearing race? I've got the driveshafts off. Will take some pictures later and I can show you what I'm working with.