Scary vibrations at 120 km/h...
 

When I drive around 120 km/h, I get that big, annoying, scary vibration... like everything wants to collapse... or almost. The vibration is strong enough to make skip my CD player. And it is worse on compression. But goes away under load at 125 km/h +... as a matter of fact, it acts like a champ at higher speeds.

I thought about the engine holders (is it the word???), and I know my tranny needs a rebuilt...

Does any of you has any idea on the source of my problem?

Thanks

Wheels out of balance?

possibly driveshaft balance

I had a wheel balance issue at about 90-100mph.

And yeah, driveshaft could be outta whack too.

I'd say have the wheels balanced first to see if that fixes the problem. I would think its cheaper and easier to do than balance the driveshaft, but I can't say cause I've never balanced a driveshaft
-Ben Martin

all of the above with the addition of u-joints. have you checked for play at the u-joints on your driveshaft?

you have to take it somewhere to get balanced. i can do my own wheels.

my friend had a problem with the driveshaft balance and it was BAD. and after fixing there is still something going on. not sure if something got misaligned in the rear end or he magically bent a rim.

Motor mounts fused? But that usually means the vehicule shakes all the time (In Semi's at least... don't know if car motor mounts work the same way).

this sounds most logical, unless your tranny mount is out and allowing the trnny to move over and put the drve shaft into a lil bind. i would start at the drive line, if tires are out of balance you would feel them even more in the higher speeds.

I had a similar problem. The drive shaft was shot. Also I had bad tires. New drive shaft and tires cured it.

I had a similar problem where my car started vibrating like crazy above 50 mph. I found out that my u joints were rusted through and like cracking, so my driveshaft was making an elliptical motion. Check that out, that is most likely the cause.

driveshaft....

What do you need to balance the wheels yourself? I don't trust any of the mechanics around here with any of my cars.

uhm, work at a shop w/ a balancing machine lol

Just ask around at high end car shops as they usually have bling ass wheels that people would castrate if you scratch them. Or find a bling ass wheel dealer. Just tell em to be careful and be kinda anal if you have nice wheels.
Balancing wheels isnt a big thing as long as they can put your car on a lift properly, and then theres not scratching the wheels which can be avoided by using stick on wheel weighs on the inside of the wheel and not on the lip.
-Ben Martin

When I bought my RX7 last month, I had a vibration problem; but only at highway speeds. I rotated the wheels front to back and it made it worst. I took it to (an experienced) tire shop and they verified the original balance was good on all four wheels BUT...
The aftermarket rims were not fitting the hub tightly and they ordered me some hub centric rings. They explained that they not only center the wheel on the hub, but it puts the weight of the car on the hubs and not the studs. It was recommended for SAFETY.

Also, when they spun the wheel for balancing, they noticed two rims were bent. That is why rotating the wheels intensified the hop and I could feel it in the steering wheel, too.

Now, I'm debating to replace the two bend rims or all four...

Check that your rims fit the hub snugly; that they are balances; that they are not bent; hand torqued to 90 lb, (not air wench torqued); proper tire inflation.

I had the same problem just after I bought my '88 TII. It was fine untill I hit around 120 km and then it would vibrate (not quite as bad as you describe). One of the stock rims was slightly bent and when I put my new rims on the vibration went away completely. If it's the driveshaft you would be able to hear a "clunk" when you put it in gear and take off (if it's bad enough to cause that kind of vibration). My guess is that it's an alignment problem.