93 Grand Caravan 3.3 Shimmy part II

Well, I had the tires balanced today and the shimmy is still there. It
seems to come in at around 15-20 mph and then goes away around 40 mph and at
highway speeds is fine. The motor mounts are fine, I replaced them last
year. I replaced the timing chain last weekend and needed to remove the
passenger side motor mount. I know these can be adjusted slightly. Is it
possible it did not go back in the same position it was in and causing the
problem ? I did not loosen the front or drivers side mount, so I wouldn't
think it could be far off. And I don't know if this would cause a shimmy.
The Haynes manual said a possible cause could be worn rear bearings and I
will check those tomorrow. Someone said it could be a worn inner cv joint.
Is there a way to check for that ?

any other suggestions would be helpful,
thanks,
Nick

 

Not without removing and disassembling the axles. If you determine you want
to remove them do one of 2 things. Either put 2 remans in or take the ones
you pulled to a good rebulder and have them rebuilt. This is probably your
better bet but some would argue with me but frankly I've had WAY too much
trouble with buying the remans and so have others I know. I have a very good
rebuilder nearby and the cost is the same so it's the way I'll go from now
on.
Now other things can cause this symptom. 1. Bad tires (very common)
balancing will NOT help. 2. Corrosion on the wheel hubs causing the rotors
and wheels to not sit true. Cure remove the rotors. Using a wire brush
rotary tool remove any corrosion on the hub, rotor plate, back of the wheel
etc.
Larry

 

I had the same problem with the same model and year van. It turned out
to be a bent rim. Replaced the rim and the shimmy disappeared.

 

Ron;

With your bent rim, did the problem go away at higher speeds ? I would
think if the rim is bent, the shimmy would be there no matter what speed you
were driving at. Maybe the shimmy is just more pronounced at the slower
speeds.

thanks,
Nick

 

One other thing, the wheels are those aluminum alloy wheels and not the
steel rims.
thanks

 

Vehicles respond to imbalances differently at different speeds - it's
called "resonance". At a resonant frequency, parts of an object
(vehicle) can shake with more displacement than what the excitation (the
displacement of the actual bent part) is. At other frequencies (vehicle
speeds), the same vibration gets damped out and may not be noticeable.
This is often seen in vehicles with slightly out-of-balance or
out-of-round tires where the shake is felt at, say, 47 to 49 mph, but
hardly noticeable, or not noticeable, at other speeds.

Also sometimes a vibration can come and go. This can be caused by more
than one tire/wheel being bent or out of balance. As the vehicle
travels, the very slight difference in tire diameters (or going around
turns) can at times put the two imbalances in-phase with each other,
reinforcing (adding to) each other and being noticeable, and at other
times being out of phase with each other and mostly canceling each other
out so that the shake is not felt. This is often the case when a shake
comes and goes under otherwise identical conditions with no other
explanation.

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")

 

All the more reason to pay attention to my post.
Larry

 

Larry,

Thanks, I plan on having someone check the cv joints. The passenger side is
a couple of years old, had to replace it when the ABS tone ring cracked. I
had the tires rotated and balanced the other day. No change. The problem
is somewhat intermittent. By that I mean there are times when it doesn't
shake/shimmy, but more times than not it does it. Also, it seems to occur
only between 20 and 35/40 mph. At speeds higher than that it is gone. A
real puzzle. I would rather it be a bad tie rod or ball joint, but those
are good.

Thanks,
Nick