Vibrations At Certain Speeds

[harvs]

Hi

 

I cured my previous vibration problems (prop shaft connection) but now seem to have another problem.

 

I first noticed it when on the motorway for the first time. At around 65-70 mph, some part of the drive train makes the car vibrate somewhat alarmingly!

 

Last night I put the car on axle stands and ran it at various speeds. It started to vibrate again at 65-70, but the vibrations seemed to go away at around 80. At 100mph, it seemed relatively smooth!

 

So I'm guessing that there may not be any loose fixings and that it could just be the way the car is - with a resonating vibration at particular speeds.

 

Has anyone else had a similar issue / think this is a valid conclusion / or can think of anything I can try to do which will fix it?

 

Cheers

Harvs

[Guest Ian & Carole]

Harvs

 

That sounds like classic rear wheel balance to me.

 

Have you had them done.

 

Just also chech all the wheel nuts are tight obvious but has been known of in the past.

 

HTHs

[Guest peter2b2002]

in my 2b i get vibrations at 2800 /3200 revs , so depending which gear i'm in 20/30/40/50 mph so I have to either use a lower gear or go slower to stop the vibration , car has always done it from when it was 1st on the road, had up on jacks still can't find which panel is vibrating

peter2b

[harvs]

That souds like classic rear wheel balance to me.

 

Good thinking, thanks Ian. I took it to have them done at lunchtime - needed 25g and 35g on the back wheels. It still vibrates a bit at 65-70 ish, but it seemed a lot better on the short test trip I did. A bit uncomfortable at those speeds, but it didn't feel like something was about to drop off

 

Cheers!

Harvs

[Guest mower man]

Try a dodge Ipicked up from a Simca [ it was areal car honest ] factoryrep back in the days when petrol was 4 shillings agallon , open up a jubilee [hose ] clip and fit to prop shaft run GENTLY up the road if vibs are present slacken off and move the clipround the prop a few degrees retighten and retest if it is worse move the clip in the oppo direction it,s a bit of a faf but I have balanced out vibs on quite a few motors using an old but vastly experienced guy,s tip HTH mower man

[harvs]

Update....

 

The vibrations are staring to annoy me now, so I've been living with them be generally keeping at 60mph ish. I've done some further tests tonight - running in the garage on axle stands with the wheels and hubs off. I've wedged each side so that only one side is running. The vibrations kick in with either side locked. So I think it must be the prop shaft or diff causing it.

 

I'll look to take off the prop in winter time and get it balanced or get a new one.

 

But I did notice that the diff was pretty warm / hot. I'd run for <10mins, although I did have it over 100mph a few times.

 

Is it normal for the diff to heat up like this? (I've checked that it has oil in it!)

 

Mower man - I like the sound of your idea. If it didn't take me all evening to remove the gear stick each time I needed to access the prop shaft, then I might have tried it!

 

Cheers

Harvs

[Longboarder]

My engine resonates at 3000 rpm. Movement is up and down. Has done it with three zetecs and the pinto. It's the engine bay panels the rubbers mount on moving up and down. I just live with it and try to avoid cruising at 3000rpm.

 

I would be very wary of running the car with the rear wheels in the air. Can you confirm it is related to road speed (ie. happens in 3rd, 4th, 5th and neutral at 65-70) and is thus drive train vibration rather than revs and thus engine?

 

Yes, the diff gets hot in use.

 

Nigel

[harvs]

Hi Nigel

 

Yes - it happens whichever gear I'm in, and in neutral. Both increasing speed and decreasing speed.

 

It would probably be easier to live with if it was at a different speed. Cruising along on the motorway at 70 isn't much fun. At 80 it's much better, but obviously not ideal!

 

Glad the diff is supposed to get hot!

Thanks

Harvs

[Guest peter2b2002]

spooky this my 2b 2 ltr efi vibrates at 2800 -3000 rpm , it sounds like a panel vibrating , to stop it I drop a gear or go up 1 gear , only happens @ about 30-40- 50 or 70 mph depending which gear i'm in

peter2b

[Longboarder]

First go through the car making sure the engine and box are bolted together and both are bolted down. Check rear of prop is bolted to diff. Check diff is bolted to chassis, drive shafts are bolted up and all suspension is bolted up and there is no play, including shock mounts. If any of these things are loose then a minor imbalance can cause a major vibration.

You confirm it's drivetrain. My thinking would be wheel balance could do it or prop. Wheels. Relatively slow rotation but can be well out of balance and far from the axis of rotation so can shake the car. Get them balanced again. Make sure they seat properly on clean surfaces, wheel face and drum surface. Do they have the right diameter centre hole to hold the wheel central on the hub. Some after market wheels don't and you need a spigot sleeve for proper location.

Drive shafts are lighter, mass is closer to the axis of rotation and they rotate at the same speed as the wheels so slowish and I wouldn't think they would shake the car as much. Diff would give noise and light vibration. You would be worried about it breaking but not shaking the car to pieces. Gearbox the same.

Which leaves the prop. Rotates at about 4 times the wheel speed and its mass is at it's surface so capable of giving a big shake. Worse if the UJ's are worn or faulty. If I were you and was sure it wasn't the wheels I would have the prop off to check the UJ's and send it to a local specialist for balancing.

And I wouldn't drive it on the road or on stands. Should have said the diff will get hotter if you make it work hard by locking one wheel.

 

Nigel

[harvs]

Hi Nigel - many thanks for your comments

 

I did a thorough inspection last week to check everything was properly bolted down, especially the prop shaft and gearbox mounts etc.

 

I'm pretty confident that it must be the prop shaft now. Having run it without wheels and hubs and one side at a time must rule out the wheels and drive shafts.

 

Also, what I did notice is that part of the rubber cover which fits over the spline joint in the prop had perished and created a hole - though which the lubricant had been flung out (evidence all over the tunnel sides!). I did a temporary fix and taped up the hole and re-greased it. On driving it this weekend, I think the vibrations were reduced.

 

I tried driving a bit quicker on the motorway - 75 ish on speedo (actually only 70 on satnav) and it's pretty smooth.

 

So I'll definitely be taking off the prop and replacing it.

 

Cheers

James

[megadodo]

My gut feeling is the propshaft. I had a Triumph Spifire that had the smae symptoms. Changed all the rear bushes, had the half shafts balanced (all based on so called professional advice from Spitfire "experts") and only when the prop was balanced did the vibrations stop. The U/Js were fine and the prop was straight, it just needed balancing.