Hi all,

I am currently grinding my teeth on a Bentley '07 GTC. History goes as follows: my buddy bought this car at a reasonable (not bargain, just reasonable) price a few months back from a local (this is Dubai) person who claims to never have driven it much (56K on the clock),and said his wife mostly used.

it had some wobble/looseness and vibrations on the steering wheel, and as my buddy is out of the country and can't immediately return due to COVID Lockdown, I offered to have a look during his absence. Took the car over to a tyre center for a balancing job, and the guys told me they couldn't get the tyres balanced properly becasue they had developed flat spots from sitting in one place at 50 degs C for too long (again, this is dubai, so the old owner's story checked out). Upon further and closer inspection, we found that the upper control arm bushings had dried out and ripped, the lower ones were halfway ripped, and both the Droplink bushings from the forward control arm to the sway bar were also gone.

So, replaced the lower forward and rear control arms, replaced the upper forward and rear control arm bushings , new droplinks, and bolted it all back together again. Took the car back to the tyre place and had the full tracking done (front and rear wheels). took it for a spin, and the looseness in the steering wheel was gone. BUT still a vibration on the steering wheel. so dished out for the new tyres (figured we might as well), had them perfectly balanced and now the constant (though minor) vibration on the steering wheel is also gone...

but there is still an occasional vibration which seems to happen during or just after the automatic tranny shifts gear? and it's not the steering wheel, its the entire car because I can feel it without my hands on the wheel (and with my knee against the transmission tunnel).

i'm running out of options but I'm really not about to give up.... anyone have any ideas? motor mounts? transmission mounts? prop shaft balancing? is this perhaps normal on a Bentley - I can hardly imagine as I would expect these to ride smooth as silk - but who knows?

The front bumper has been repaired (a bit of fibre glass on the bottom) and the door has been resprayed (minor hue difference) but I can't see any other signs of a big wreck.

any insights would be greatly appreciated.

thanks,

H

 

Hello @Dubaitechie ,
How are the inner and outer CV joints on both front axles, boots ripped at all ?

Check the rears also while at it.

As to the motor mounts, iirc the 2007 did away with the electrical actuated motor mounts, so not code if bad, if this 2007 has the electric motor mounts (you will see a plug on each) scan for a fault, and look for any brown fluid leaking from either mount, be it electrical or not.

Johnny

 

Picture of some 2005 electric motor mounts off the engine, and a picture of a 2008 and a 2014, both engines with the non electric motor mounts, the MM is shown by the red arrow on the 14.

Johnny

...

 

hi @Johnny Hotspur GT

YES I forgot to mention, the INNER boots of the axles were ripped. I changed both inner and outers to new ones as everything else was already from under the car any (the upright, the subframe, the control arms, the whole lot.

I will check the rears ASAP and reply.

Are you thinking the constant velocity joints are giving these shakes?

thanks,

H

 

​​​​​​Hello @Dubaitechie,
Just so we fully understand your comment, when you say that you replaced both the inner and outer, are you meaning to say that you only replaced the rubber boots and not the complete axle, which would consist of new inner and outer CV joints, if only the boots, then yes, the CV joints will give you the vibration, I just did both front axles on my A8L W12, both inner boots were torn, and one could see the innards of the CV joint, plus they had lots of movement from being worn out by the lack of grease, what a difference in ride afterwards.
Depending on how long your boots have been ripped, I would be looking at them, you will have to jack the vehicle up to simulate the tire being o the ground to check for up and down movement on both the inner and outer CV joints, or drive it onto a drive on lift, you just don't want the wheels hanging as that would put pressure on the axles and not allow you to check them properly.
Johnny

 

Hi @Johnny Hotspur GT ,

the car only has 56KKm on the clock, and has sat mostly in one place in the Dubai heat so my guess was that the boots dried out and broke because of that. so, yes, I only serviced the axles (new grease and new rubber boots on both inner and outer CV joints) but i did not replace them with new ones.

However, the vibration seems to only manifest after or during a gear shift (which happens to coincide usually around 70/80Km an hour). when I take her on to the highway at 120/140 there is no vibration at all. this is why I was more suspicious of the motor mounts (after all the other suspension work was done).

I will check the radial play on the inner joints (only inner boots were gone) in any case, what is the allowable tolerance? any idea?

cheers for the help so far!

 

@Dubaitechie ,
While I can not say 100% that my vibration issue was at any shift point of the transmission, I can say with out a doubt that I had a vibration at 30 to 45 mph on the back road (River Road) that was all just recently paved, so very smooth surface, yet it would vibrate, yet on the highway at 60 + there was no vibration, and as you stated, my vibration was not felt in the steering wheel, the only work I had done on the vehicle was to replace the alternator as it blew out in March, so while in there, both front axles were replaced, the outcome is no vibration.

There is another member on here that had an issue that turned out to be the output shaft on the right side of the transmission the connects to the axle/CV, it had up and down movement, BUT he was way up there in mileage as I recall.

So do check the axles for any up down movement, check the motor mounts for and leakage, check the transmission mounts, and possible check the condition and level of the transmission fluid, REMEMBER, do not pull the transmission plug without the engine running, the vehicle engine/trans must be at operating temperature and running to remove the transmission check/fill plug, if you pull it with the engine off, the transmission fluid will pour out, did that myself years back on my first time...


Because we don't know for sure how long the boots were ripped, and you have 122°f temperatures with sand/dust, I would bet those elements would wreck havoc on the CV joints open to the elements in no time.


Johnny

 

Roger That @Johnny Hotspur GT

will check and let you know the outcome

thanks a million.

H

 

I don't know if this will help, but it is worth at least checking. I had my car in for repairs for more than three weeks and when it came back off the car carrier and I took it for a quick spin, I had weird vibration and stuff similar to you are describing. I had no idea what it was, I drove it back out to the shop. I told them about the weirdness, the tech took it for a drive, confirmed it wasn't driving correctly, they put it on a hoist and found two things that fixed everything.

First, was the rims, one of them was out of true and had been bent at some point. It had been on the left front, they put it on the right rear to see if it was the cause. It wasn't but it made it drive better.

Back on the hoist and wouldn't-ya-know-it, the one thing I was sure wasn't wrong, it was the left front wheel bearing. Had too much play in it. Didn't seem enough to cause he problem, but they replaced the wheel bearing, I had the wheels taken off, straightened and powder coated (looks beautiful it was a great idea and not expensive, like $200 US /wheel) and the car now drives like a dream.

So it may be deeper than your rubber...it really wasn't much play in the wheel bearing for it to drive terribly. It would hunt all over the road.

Probably not your problem, but for those others reading this, if you aren't the only owner of the car, there is a non-trivial chance some dork has creamed a couple of potholes with your wheels and it seems the front end of this car is pretty sensitive to everything being in balance.

And...powdercoating is very nice, I recommend that, my wheels flaked off and looked terrible. My servicer took this photo in their parking lot after the wheels were put on.

 

Hey @Johnny Hotspur GT ,

so got the car on a ramp today and checked the radial play on the inner CV joints.... back ones seem ok, couldn't detect any noticeable radial movement on the axle shaft while pushing from below upwards. on the two front ones, indeed there is a noticeable play however it is not very large. i'd say about half a millimeter but of course it should be zero...

motor and tranny mounts are fine.

as I've replaced the rubber boots, I assume it's not going to get exponentially worse... i'm going to give it 10K km and perhaps prepare it for the next service.

thanks so much for the help!

H