Violent Vibrations at 100km/hr

[JRAT]

I'm new here, and desperate....and have a big problem with my 2000 Elantra Wagon..
After about 20 mins (apparently the car needs to warm up before it happens) on the hiway the car starts vibrating like it's possessed at the 100-110 km/hr range. I can drive through it to past 110 and the vobration stops. If I let go the gas and coast to slightly under 100km/hr, the vibration stops.

These are the trouble-shooting steps thus far and findings

1. Front left exterior CV boot needs repair. This is recent and shouldn't be the cause
2. During vibration, then dropping into Neutral the vibration goes away.
3. Tires rotated, Direction checked
4. Tires Balanced
5. Alignment done

I've taken it to several people, and after some nominal costs they determined that it's prob the transmission. Transmission people took it for a spin and noticed nothing on their little computer hook up thing. The same people suggested that I drive it til something obvious breaks, cuz now they don't believe it's a mechanical prob with the front end as I thought it might be.

The car has 255,000 kms and doesn't owe me anything, but it's held up quite nicely over the years with no major repairs other than wear/tear. The body is in good shape, minimal rust (must actually look for it)... so it would be a shame to let it rot.

If it really is the transmission should I get it re-built, or drive the thing til something breaks then fix it... ??

PLEASE HELP

[Gregster]

You didnt mention it, but how do you engine/trans mounts look? Are they in good shape?

Greg

[KeWLKaT]

sell it to me haha

[DJ Hellfire]

Here is a few things it could be:

Defective tires: meaning high runout or broken internal belts. Thnigs that balancing will not fix.
Bent rims: no matter how many times you balance bent rims, they may still cause shaking.
Improperly fitting rims: If you have aftermarket rims, they will sometimes cause shaking if you do not use a hub centric ring or if the hub centric ring is not the proper diameter.
Bent hubs: Normally caused by over-tightening wheels with an impact gun or curbing the car.
Excessive wheel bearing play: Will basically allow your wheels to wobble. May even cause loud humming.
Loose inner and/or outter tie-rods: This will basically allow your wheels to turn slightly without the steering wheel. At high speeds, this is bad. However, this is unlikely the cause because they shouldn't have done an alignment if these parts were loose.
Bent axle/s: Pretty obvious!
Bad engine/trans mounts: This may allow your engine and trans to move more than it should which can shake up the axles a bit.
Bad lower control arm bushings: These things pretty much just wear out over time, but the biggest killer of these is from oil leaking on them. Check for any fluid leaking on them. Should have been checked before alignment.
Loose lower balljoints: Again, should have been checked before alignment.


That's just to give you some ideas. But there are more possibilities. Good luck!

[chillbro1]

If it were me...I'd check...

Engine Mounts, Trans Mount, first....and considering the mileage I'd say it probably about time for mounts if you have not replaced them already.

If those are okay...you probably have an internal trans issue...and I would particularly suspect a torque convertor since it seems to be a rotational issue. Torque convertors have counterweights on them...and if the weights come off...then it would not be unusual to have a hellacious vibration.

I'd eliminate rims and tires and all that stuff because you said it stops when you put the car in neutral.

If it is the trans...in all honesty, Hyundai Remanufactured Transmission are cheap enough that you could probably get one cheaper than the cost of trying to rebuild it, and the Hyundai Reman is basically like buying a new trans...they replace just about everything...and basically the only thing that is reused is the trans case from what I have heard. They are remanufactured at Hyundai Translead in Mexico...with HMC engineers on site. Same is true with the torque convertor...you could just replace it if it was deemed bad...but the torque convertor costs almost as much as a reman trans (at least here in the U.S.) so again...I'd spring for the reman trans.

Hope this helps you out....

Peace,

[extremeaudiowa]

Trans or Engine Mount, Ive got a 1997 Elantra Wagon and had the exact same issue

[JRAT]

Thanks for the replies.. Lots to think about and test..

Yes... In neutral there is no vibration at all, so it's tough for me to think that it's a "moving parts" thing (tires, shaft etc)... And that it only happens when the cars "warmed up".. Lots of aggravation

One mechanic guy mentioned that the rear mount is cracked, and needs replacing, which could cause the prob... Another mechanic mentioned that they don't need to be replaced.... It's not a big cost, so I should get that done.. Tranny guy took it for a spin and notice that Speed sensor wasn't working..Is that the same as the torque converter??

I can change the CV boot and both front shafts again a for a ressonable cost.
And a close friend of mine did notice that the torque converter wasn't engaging.. (I had to trust him).. he made me tap on the breaks on the highway etc, and according to him, but then again he also said that that should be a biggy either and that i would not get the "economy" milage.

If after replacing the shafts and rear mount, a reman'd tranny seems to be the best thing... The rest of the car is solid.. a couple of tiny rust spots, but other than that it's been a star.
I's hate to toss it if it only needs 2 grand or so..

BTW, I would assume that it would be best to take it to my Hyundai dealer for a tranny if it gets to that..

And KeWLKaT.. If I can't fix it it yours..!!!