Vibrations under acceleration

Hi Guys,

yesterday at Knockhill I discovered a new problem.
My car vibrates very strongly under full throttle.
The vibration seems to be coming from the rear, as if it was a very out of balance wheel (or both), is stronger the more throttle I give, happens between 55 and 100 MPH (with a peak at 60 and 90) and dissappears when I release he throttle (even if at 60 and at full chat).

Now the car was perfect the last time I drove it, and the only difference is that I had it at the Lotus dealer in Aberdeen for service, where they coincidentally found a broke CV boot and booked the car the following week to change it.
I didn’t drive the car meanwhile, and from my house to the dealer I don’t do 60 or 90. Even less full throttle.
Now, I’m going to call them of course tomorrow, but since I have no idea where can this come from, wanted to check the collective knowledge first.
Obviously they assembled someting wrong, but… what?

Wheel balance is out of the question because on partial throttle or coasting there is no vibration.

What could it be?



Sounds really like a CV problem to me … Possibly the inner one …

Hate to say so, but I agree…

They do say that if the gaiter gets cracked the joint is much more likely to fail…


I think its consitant with at least starting with the CV… its pretty much the obvious starting point given that they have been in there. I think you are right in that it doesn’t sound like wheel balance (which would be there if on or off throttle)

Anyone know how to do any kind of preliminary check to prove?? jack-the car up, engine off, in gear and manipulate the rear wheels to look for play ?? or grinding?? AndyD? Phil? da Edwardz?

pretty sure the garage will sort it out tho’

Andy, what do you mena the inner one?
Isn’t ther only one on the left and one on the right?

And then the car was perfect when I took it there, albeit with a grease leak from the CV boot.
I would guess that they would have to repair any damage if it was caused by them assembling it wrong, not?

And Mike(L) you mean that the CV boot leaked becasue of a crack? but then the symptom would have been there even before, right?

And Rox, there is no strange or grinding noise, just the vibration.

Hmm, I would have to assume this never happened to anybody here?

My understanding is that the gaiter can ‘perish’ and loses its elasticity, which leads to cracking / splitting. and then both loss of the lubricant, and possibly ingress of dirt / dust / gravel pieces, so the joint quickly dies from the effects of lubricant loss and accelerated wear…

I see, but when they noticed the broken boot, they said the joint was still fine, since it had just happened.
They even said that I could drive it for a few days until they got the boot, but I garaged it and didn’t use it.

I hope it’s something easy to fix…


There are two joints on the driveshaft - the outer CV and the Inner CV ( the one that goes in the gearbox).

My experience with high power/torque Minis was that a vibration under acceleration, that went away when you lifted, was the inner joint shagged … and I changed a few

I worked out the inner “pot” joints were crap and used the far more agricultural Hardy Spicer type joint …

I know they may have not touched that, but if they pulled the shaft out or let it droop when they changed the outer boot they may have caused a ball to drop out.

Thanks Andy, that kind of experience is what I was looking for.
Now, I’ll have to try convincing them that they should be responsible for that…



Just a thought … you have checked engine mounts haven’t you ? You know, grabbed the engine and tried to rock it ?

Yep, even put on the handbrake and on 1st gera and reverse while easing the clutch abit to see if it would move but not.
Couln’t be the mounts.

I had a nasty vibration after about 1000 miles when the driveshaft broke! Lotus said it was the first on an Exige and down to a faulty bearing.



How did you get on with this today??

I have a few quid running on AndyD being bang-on sotospeak

Don’t remind me.

Told all the symptoms to the dealer and told him precisely that the vibration happens between 60 and 90 only if at FULL throttle.
They said they would not think the CV boot was badly installed, but would check it out.
He called me in the afternoon and told me the car was ready.

good! I said, what did you find?

but what did you do?
-revised it all well!

did you dive it to reproduce the vibration?
-yes, and no vibration

Did you drive between 60 and 90 at full throttle?
-no, we can’t brake the speed limit, so droive it nicely around town.

But I told you !!!

They didn’t want to believe it was the inner CV and didn’t disassemble the thing, just went for a SLOW ride!!!

AAARRRRGGGHHHH !!! How can people be soooo stooooopid!!!

Told him I would not take the car back and would go there to drive the car to show them.
He agreed and now let’s see what happens tomorrow.

That was the Lotus dealer, problem originated by the Lotus dealer.
That was my safest option.
As soon as this is over it’s another mechanic, non-Lotus for me.
Will try Bob Duncan.


He doesn’t have to break the speed limit at 60mph on full throttle!!!

This kinda stuff is just plain annoying I have had the same many times… drive 70 miles to the dealer, give specific info about a grumble and then go back to collect the car only to find … well… they couldn’t find anything… errmmm do these guys actually LISTEN to what we say?

grump !!.. hope you get it sorted tho’ and hope they are big enough to own up if they have damaged the CV.


Went there today and took the guy for a drive.
Showed him exactly what happened.
He suggested that it might be wear and tear then , to which I said how could that be if he told me that I had just brought the car in time, as it was only a pinhole and most of the grease was still there. Besides, it was not vibrating before them fiddling with it.
Very long talk folowed and we ended up with the Service Mgr, who is also the Mgr for Porsche, Lexus, Subaru and Lotus.

Everything was explained again and the fact that the fault was not there before.
He brought out the fact that it happened on the track. Nope, I said it didn’t happen there, I just noticed there because I don’t drive in the city or motorway at full throttle over 60, so can’t be seen.
He mentioned that they would dissassemble the CV joint, and if they found thet it was their fault, they would fix it on their cost, but was quick to point out that if it wasn’t, that I was liable for the charges.
To which I said to go ahed, that I am pretty confident, because the problem was not there before.
He mentioned he didn’t know that for sure.

Now, I did a good job of behaving there, because I don’t like anybody implying that I’m lying trying to trick them.
If they don’t accept liability, I’m going to escalate, until they do.

A dealer cannot, should not just do this and get away with it.

If you guys have any tips, I’d be happy to hear them.


Ouzi 9mm ??

Seriously though, I know how you feel, but I would also try to look at it from their viewpoint before escalating too much…

Components do wear out, and sometimes coincidences are bound to happen…

Fingers crossed that they find they’ve put something in back to front, and it can be amicably sorted !!

Yes, in fact. And today’s update is this:

Received a call from them to go and see the dissassembled CV joint.
They made me note that it was worn.
As you can (hardly) see in the pictures, two of the splines’ sides were very worn, like 1.5mm deep (I suppose that is enough to eccenter the shaft and feel the vibration).

BUT one of them was not worn at all.

CV joint 1
CV joint 2
CV joint 3
CV joint 4
CV joint 5

I know it’s difficult to see but there is only deep wear on two of the splines, and the spherical parts on the tripod looked good, the circlips have not been dettached and none of the bearings had fallen. But yes, in one position, if you fall into the groove, there’s about 3mm of play (enough for the vibration?)

Now, their point is that there is no way wear like this can happen in 200 miles, so it was like that before.
My point is that there is no way wear can be found naturally only in two faces and the third one be perfect.
Also, why then I could feel vibration only after they touched it?
Could it be because of installing the tripod joint slightly rotated? ie not in the same position?

Their position is that the wear might have been there but on assembly if they rotated the tripod the vibration might have started.

My position is that if the wear was not there start with, the rotation of the tripod might have worn it. Because it’s only two sides that are worn, and that is very strange to me.

So, they’re going to fit a new shaft anyway and as a gesture of good will, waive the labour and they are going to call their field engineer (who they say is a third party contractor).
If he says that the wear could have been caused by the incorrect positioning of the tripod, they absorb the charges, if not I pay (only the shaft price)

What do you say?


Reckon you have a good result, even if you have to pay for the new parts, cos the labour will be free in any case !!

Add to that you will now have a new joint, rather than your quite worn ( judging from the piccies ) old one…

And if the third party agrees you may be wearing a big grin for ages

Being pragmatic, it sounds like the best deal you could have got - should the centre have been packed with grease and is it possible when they reassembled it initially they forgot to?