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Discussion Starter #1
Hi all,

I'm a little stumped with a vibration that has suddenly appeared on my '81 GTV6.

This car was (mechanically) entirely rebuilt two years ago and passed its MOT with flying colours both at the time, and its latest one a couple of days ago. It has never had any problems when driving since the rebuild; on the contrary it has been absolutely brilliant.

I don't use it every day as I'm a busy person; admittedly until recently, it had been sitting for a few months (in a barn). I took it out again a couple of weeks ago, just to charge the battery, flash it up and go for a spin around the village. No problem.
One week ago, as it had run out, I booked an MOT not suspecting any issues. On the way I notice a vibration I didn't remember before. Which got progressively worse - to the point that 4km down the road I decided to stop (first chance I had anywhere safe to pull over), couldn't see anything wrong underneath. My dad was with me and we both reckoned rear right wheel. Went off again, it came back within 500m and pretty bad, so I turned round, limped home and had to apologetically cancel the MOT as I didn't want to risk anything bad happening.

I'll point out that I had already tried the obvious in the car, put it into neutral and accelerated - zero vibration from the transmission, which I had been especially careful with during the rebuild and researched carefully to make sure I did it properly. Also this wasn't a problem after the rebuild, only in the last couple of weeks. It was clearly related to the speed of the wheels going round.

We spent the rest of the afternoon jacking up the wheels, checking them over, absolutely zero play anywhere - no surprise considering the recent rebuild not many miles ago. We then tried running the car on axle stands - both rear wheels ran true, no deformation or play, no wonky movements - all nice and straight as they should be. The obvious answer would be a tire that had deformed through standing too long; however having removed and inspected all four wheels neither of us could see or feel any form of deformation whatsoever; the tires looked perfect and completely intact. Nothing obvious and nothing especially to justify the kind of vibration that was felt in the car.

In the end we swapped front wheels with rear. The vibration seemed to mostly disappear, but at that point I wasn't sure how much I was imagining and how much I was actually feeling. it kind of felt like it wasn't coming so obviously from the rear any more and was so distant I was quite happy to drive it like that - to the re-booked MOT and back anyway.

Jump to yesterday, MOT day take 2. Take it out, no problem. 10 minutes later the vibration suddenly appears again... ****. At that point I'm closer to the MOT center than home so decide to take it easy and not turn back this time - if there's anything obviously wrong, he ought to spot it.
Got there no problem, it passed with excellent results as before, and he didn't notice anything wrong. In all honesty, fearing a fail, I didn't mention it either.

On the way back I tried what I could to figure out where it was coming from and what triggered it off. I had another passenger - who wasn't aware of the first time - who reckoned he wasn't sure, but he felt like it was coming from the front more than the back.


What I have figured out so far:
  • it's not engine/transmission related, but something further along and clearly thudding at the speed of rotation of the wheels.
  • it is progressive. I drove about 10km before it started again the second time. The more you go, the stronger the vibration/thudding gets.
  • Sometimes coming to a stop and starting again helps. But doesn't always entirely eliminate it.
  • it definitely happens and gets worse when braking. However if it was a warped disc (which I really don't think it is considering it started happening after a few months standing and was absolutely fine before that) then surely it would only happen when breaking, not the rest of the time as well.
The last and most decisive test would be to try another set of wheels or tires, but I don't have a second set to diagnose with and am a bit loathe to buy another set of tires, when these are as-new and may or may not be the cause of the problem. I don't even have a spare wheel to diagnose one at a time (I only found out last week that my spare wheel is from a Volvo and definitely does not fit a GTV6.. yes I am now looking for a spare wheel before I need it!)

hence posting here in case anybody has any thoughts on things I could check first, anything I may have missed.

One other thought which may or may not be related: OK, I overhauled all of my mechanicals two years ago (including taking apart, cleaning up and fitting new seals to all four calipers). But after a few months of standing the rear discs aren't quite stuck, but the wheels (when jacked up) aren't spinning freely as they should; they stop when you let go. So they're gripping a tad. Doesn't seem to affect performance, or the results at the MOT. However (and I don't know the answer to this - which is why I'm asking) is it possible that slightly gripping brakes aren't getting on too well with the diff which is trying to make the driveshafts move? or is that question irrelevant seeing as it happens in neutral too?

Any thoughts appreciated as I'm a little stumped here. If it is a deformed tire I would be surprised that it could cause what ended up being quite a strong 'thudding', and surely it would vibrate all the time, not get progressively worse after braking?
 

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My guess - only a guess - is that it is tire related. Usually a broken cord will reveal itself by a bump that can be felt if you run your hand around the tread (be careful - I've seen steel belts poke through the rubber which can slice your hand). But perhaps there is some internal fault that is not so obvious. If you can find a shop that can do a 'road force' test they should be able to rule in or out a tire fault.
 

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Discussion Starter #3
My guess is that too... However we certainly could not see or feel any deformation or irregularity of any sort on any of the tires, either on the tread or the sidewalls.

By road force test do you mean the rolling road and vibrating suspension test? Both of which it went through during the MOT yesterday, good results, equal measured on both sides.

I have little to no experience of tires going wrong in any way, beyond a puncture in a rear wheel on a van once which was heard more than felt. Consequently I am not familiar with the signs of problems, though do find it odd that it was vibration free for the first 10km and got progressively worse, especially after braking, to the point that it was less of a vibration and more of a big thud-thud-thud each time the wheel went round. Made you think the wheel had a half inch pebble glued on to it at its worst. Then pull to a standstill and set off again, and it's not so bad (for a bit). Very odd.
 

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Also, check that your CV joints, driveshaft and giubo bolts are snug.
it’s probably not those, but they aren’t something you want to come loose.
And what about deDion and gearbox mounts..all tight? Calliper bolts?
Check every nut and bolt you can find, if only for peace of mind.
 

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Discussion Starter #5
Also, check that your CV joints, driveshaft and giubo bolts are snug.
it’s probably not those, but they aren’t something you want to come loose.
And what about deDion and gearbox mounts..all tight? Calliper bolts?
Check every nut and bolt you can find, if only for peace of mind.
Good point - certainly no harm in double checking things. I was pretty mad on thre loctite upon reassembly, but you never know. Only takes a bit of time to check for peace of mind.

I have managed to find a full set of 5 GTV6 wheels the same as mine - with tires - advertised locally (what are the odds in rural France) for a very fair price. Hopefully nobody has beat me to them, will try to get them to have a spare wheel, a spare set of tires, and be able to diagnose whether the issue is actually coming from wheels/tires or not. Hopefully they're not already sold...
 

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By road force test do you mean the rolling road and vibrating suspension test? Both of which it went through during the MOT yesterday, good results, equal measured on both sides.
Road Force testing is similar to dynamic balancing - done with the wheels/tires off the car but it adds a load to the tire tread to mimic the flexing of the tread & sidewall that would be experienced when driving. Another thing to remember is that a square tire can be balanced but it'd never ride smoothly.

 

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Do I have this straight? You have a low frequency vibration after driving for ten minutes or so, it’s speed related, faster you go, worse it gets, regardless of what gear you are in. Yes/no?
And your brakes drag.... what are the pad gaps at the rear?
How fast are we talking? 50kmh? 100? 150?
Does it change when braking? Does the steering wheel shake?
How long do you think till you have a functioning spare tire?
 

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I'll tell you what happened with my 86 GTV6 one time. After a spirited run on a curvy mountain road, I started to get a thumping/banging sound. I stopped the car and checked around outside, saw nothing odd. After a short while I started off again, and this time there was no banging sound. After a while, though, it came back after dropping down out of the mountains. I thought, hmmm, what gets hot after driving a while on curvy roads.

Ah hah, it came to me. The brakes. After I got home, I took the front tires off and looked at the brakes, both discs and calipers. What I found was marking/scraping on the inside of one caliper and matching shininess on the matching disc.

Turns out the problem was that the disc hadn't been trimmed true, and had a bit of excess flange sticking out, and when the brakes got hot, the disc expanded radially enough for that excess flange to impact the inside of the caliper. The as delivered GTV6 discs are just a little tight, barely fitting within the calipers, and if the disc is not perfect, they can interfere when hot.

Bottom line, I had to have the disc turned true and then all was fine ever after. Actually, I had both front discs turned slightly smaller in diameter to match, just for heck of it.
 

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I had a set Kumho tires on a beater car that started to de-laminate.
The vibration started at about 45 - 50 MPH.
Tire Rack bought them back from me because of a factory defect.
The defect was tiny letters that said "MADE IN CHINA"...
 

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I'll tell you what happened with my 86 GTV6 one time. After a spirited run on a curvy mountain road, I started to get a thumping/banging sound. I stopped the car and checked around outside, saw nothing odd. After a short while I started off again, and this time there was no banging sound. After a while, though, it came back after dropping down out of the mountains. I thought, hmmm, what gets hot after driving a while on curvy roads.

Ah hah, it came to me. The brakes. After I got home, I took the front tires off and looked at the brakes, both discs and calipers. What I found was marking/scraping on the inside of one caliper and matching shininess on the matching disc. The as delivered GTV6 discs are just a little tight, barely fitting within the calipers, and if the disc is not perfect, they can interfere when hot.

Turns out the problem was that the disc hadn't been trimmed true, and had a bit of excess flange sticking out, and when the brakes got hot, the disc expanded radially enough for that excess flange to impact the inside of the caliper.

Bottom line, I had to have the disc turned true and then all was fine ever after. Actually, I had both front discs turned slightly smaller in diameter to match, just for heck of it.
I was just going to say it might be one or more of the brake calipers dragging, and expanding with heat as the car drives. A quick check with an infrared heat gun (or holding your hand near the offending brake caliper) would be an easy way to check this.

Besides actual brake hydraulic issues, or rear caliper pistons adjusted too tight, make sure your rear parking brake cable and levers are free and not dragging.
 

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The brakes do heat up a certain amount during normal driving, causing no problems in almost all cases. After a run to the store and around and back in my 91S, the front wheels near the bold pattern measure about 95-100F and the rear ~85F, ambient air being ~65-75F. Obviously the wheel values would be much higher if I did a spirited drive, as I really did with the GTV6 that time. It does seem that the GTV6 discs chosen for the car when new were evidently maybe too close to the caliper, and if there were any imperfections, the increase in diameter from heat could cause the contact.

A simple inspection for contact marks on the caliper and disc rim would tell you everything. Nothing to lose.
 

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This is a common problem on the Gtv6 and Milano. Check the upper control arm inner bushing. They tend to separate allowing the upper control arm to bang back and forth in the body. To test, use a pry bar and move the control arm forward and back. If it slides enough either way to hit the body, you have found the problem. Btw this is very frustrating because the vibrations can be very intermittent when the bushing is just beginning to fail.
 

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Discussion Starter #13
Thanks to all for the input - really, more heads are better than one and the more ideas to look at, the better.

By a miraculous coincidence for somebody who lives in the middle of nowhere in the french countryside, after posting my initial message I spent the evening looking for a spare wheel, and found a full set of 5 GTV6 wheels with tires, for a very fair price, 1 hour from home (for where I live, that's not that far). I sent the chap a message in the hope he might see it short term - as the next day I was actually working half the distance in that direction anyway - as it would have been more than convenient to buy them before or after my job. He answered the next morning during breakfast, and an hour later they were mine.

Today I cleaned them up, checked them over, made sure they held air, and fitted them to the car. I was going to test it but got distracted, so will do tomorrow. With all four wheels and tires changed (and a spare in the boot now, for peace of mind), this will obviously determine whether they are at fault or not. if they're not, it's no loss - I'm quite happy to have found a spare wheel, and a spare set of wheels with tires in reserve is always handy.

On the same day, my job a for a chap equally into classic cars, and I told him what was happening; he told me it sounded awfully similar to what happened to a Jag he used to own, which was indeed caused by rear brakes sticking somewhat (more so on his case by the sounds of it as his car braked by itself when releasing the throttle, whereas mine isn't that bad and doesn't). If the wheels/tires aren't at fault that's obviously what I'll check next - I know they're sticking a little bit as they stop turning when you let go when up on the jack.

Front discs are still the old ones as they had plenty of meat left on them, really no need to change. Front control arm bushings are new (2 years old) so an unlikely culprit. The handbrake adjustment on the contrary is too free - the MOT guy said he had to push the pedal slightly to help it along to pass the reading, and told me I ought to adjust it up a bit. My tires aren't chinese specials, the previous owner bought some pretty decent ones. The change to new wheels and tires will tell if they're the problem or not when I take it out tomorrow.

I'm leaning towards brakes as I now they stick a little bit (so need freeing regardless), the getting worse with heat theory adds up, and we really couldn't find anything at fault with the tires that were fitted at the time. The calipers were totally overhauled so it'll just be a bit of sticking from lack-of-use corrosion over the winter and spring. Also because that would be the most convenient and cheapest solution to the problem :D

I'll be back with the results!
 

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My experience matches CDA51 and Del's on a recent sprint through the mountains chasing a buddy's Alfetta. The thump thump thump began on a downhill and I immediately thought that I'd overheated the brakes. Backed off for several miles and the symptom disappeared.

I'm not discounting a prior poster's concerns about the bushings. However, in my case the front end had been entirely rebuilt.
 

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Steering track rod end gone bad? I noticed mine had a lot of play on one side. But I didn't notice until jacked up. I guess it could have the wheel "wobble.

Here is a video uploaded to another Alfa forum showing it.
 

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Discussion Starter #16
OK, so it's not wheels or tires - same thing with the new ones. I don't consider it wasted money however as I'm quite happy to have a spare set of wheels (and a spare too now).

Deffo not bushings or track rod ends - everything is new. Every mechanical part of the car is new. Nothing is worn.

I'm certain at this point that it's the rear brakes, as they're slightly gripping the discs. You can turn them, but when you let go, they stop.

MOT had good results however, and if anything the guy told me to tighten up the handbrake.

So I looked at it just now. Put the car in gear, chocked the front wheels, released the handbrake. Pads still stuck against the discs, no gap. Loosen the handbrake cable to start from scratch, go to the four adjusters to reset the gap between the pads and the discs. And nothing works anymore, only two of the adjusters are doing anything on the RHS wheel. The handbrake levers on the calipers are free and moving. I cannot whatsoever get the adjusters to move the pads at all on the LHS caliper. With the handbrake fully untensioned. I did eventually get a gap when I completely loosened the handbrake cable, stupidly put my foot on the brake pedal a few times to make sure the pistons were moving, went back to zero gap and unable to create one. These adjusters are on threads, why aren't the pistons moving? The pistons won't return even with the bleed nipples open and a pry bar pushing against the pads to try and open them up. I've looked carefully with a torch; it is indeed the pistons not retracting and not simply the pads stuck in position in the caliper.

Bearing in mind that only two years ago both calipers were entirely dismantled, thoroughly cleaned out, seals replaced, reassembled as-new and clean as a whistle, bled through, handbrake gap patiently set correctly and no problem for one and a half years. Six months of rest surely isn't enough to have to go through all that aggro again? I don't get it, why won't the pistons return and why are the adjusters not doing anything? All fine on the front, no problem there. As mentioned previously, all mechanical parts were new two years ago which also includes the brake master cylinder, original ATE.

And this time, without the axle removed during a complete vehicle overhaul, I'm presuming there's no easy way of removing the calipers alone without removing driveshafts, discs etc... Please tell me there is an easier way...
 

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The best thing you can do for the rear brakes and the handbrake on the GTV 6/Alfetta/Milano, is to drive the car regularly, and lightly use the handbrake when you park. Keeps everything working and free.
 

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Discussion Starter #19
In hindsight, that is of course true; in reality it's not always easy when busy working nearly all the time. Guess i'm learning the hard way. None of my other cars seem to have this issue though and one in particular is lucky if it does 500km per year.

Regarding ghnl's post, that's all very well, until you get to the bit 'remove nut 6' which isn't possible without removing the discs as the gap between stud and disc is thinner than the nut, which thus cannot be removed with the discs in place. So I guess the full monty does need to be taken apart.
 

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Could it be that the adjuster threads have come out of the pistons or are stripped ?, applying pressure with a pry bar won't do anything but if apply slight pressure while turning the adjusters in the correct direction it might realign the threaded setions and then allow the piston to retract. Just a thought.
 
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