Alright, this might be kinda long - I'm gonna try to give as much info as possible.

89 GXL / 5 speed

This has just started and is getting worse rapidly - Anyway, between 2500 - 4500 RPM the car shakes violently, but only when accelerating. The vibration is comming from somewhere in the driveline (tires, driveshaft, tranny, etc). And the shifter shakes so bad it hurts to hold it.

Symptom 2 - Imagine this... you are putting around at about 20 mph, drop into first and hit the gas - at this point, when I hit the gas I hear a loud CLUNK under the car by the shifter. When I shift normally I can't hear the clunk, but I feel it in the shifter handle.

On the way home yesterday I wanted to cut loose on 1 of my favorite roads. At about 90mph the shaking got so bad I got scared and backed off... didn't want the trans or driveshaft falling off and throwing my car into the air.

At first I thought motor mounts or tranny mounts were to blame - I just spent about two hours under my car trying to find something - anything that could be fixed / tightened.... Nothing. The one thing I did find was a small tranny leak - I mean real small. It appeared to be comming from a weep hole right in front of the inspection shield.

Anyway, could U Joints be to blame, or am I missing something. If it could be the joints, can they be replaced (I remember reading somewhere that they couldn't). Just wanted ya'lls opinion before I tried - looks like a PITA to get the driveshaft out...

Jason

 

bump.....

 

Not sure, but the driveshaft actually isnt that bad getting out. Might want to take it to a driveshaft shop and get it checked out just in case, or get one at a junkyard and get it redone, then just swap them.

 

Bad U-joints will certainly cause vibration, but they are almost always noisy when they are going out. The noise will be a roar that matches the frequency of the vibration, and increases in loudness with speed.

I recently replaced my drive shaft because of a bad front u joint. I used a Mazdatrix shaft (the replacable u joint version) and was amazed at the smoothenss of my rex now. The old drive shaft was way out of balance even before the u joint went bad.

If you can access the underside of your rex after driving it for a good while you may carefully touch each u joint with your finger, then whole hand. If the joint is bad it will be warm or possible even very hot to the touch. You may also be able to detect slop by trying to rotate the shaft. Any movement at all (in the u joint itself) indicates a bad joint.

 

Driveshaft is my first bet.

PaulC

 

I had a similar problem recently. Shop I used put a decent used driveshaft on for 175.00 out the door.
A new one will set you back about 300 + labor and the u joints are not replaceable. The Mazdatrix unit with replaceable u joints is similar in price + shipping.
Hey, it's solveable. Just add money and stir.

 

Its your drive shaft, Mazda Trix shaft is kick ***!! it has replaceable joints and it has zerk fittings (grease ports), something the factory did'nt feel the need for. Dont drive your car like that too long, it will wear out your rear bearings and seals in tranny and front bearings / seals in your rear end.

 

I had same problem,. Would vibrate, especially on interstate.. VERY anoying... replaced tranny mount (it was bad anyways and caused vibes at idle) Still didn't stop vibrating when driving... heard CLUNK noises when shifting, or starting from a stop.. or trying to engine break...
A great guy on this forum had a used one he sold me cheap.. and I got it... went under my car.. removed the old one...

One of the bearings, HAD NO BEARINGS IN IT... Was cracked, broken, and wiggled... Scary.. I was driving on that for months...

Anyways put the new on one.. Voila! Driveshaft is def your problem.. no doubt...

The mazdatrix one sounds nice... Detachable ujoints.. Able to inject grease into them... Mazda stock ujoints/driveshafts SUCK... what were they thinking? OH YEA MORE MONEY FOR THEM

 

Thanks guys.....