I have a newly acquired 1989 Grand Caravan (106,000 miles, LE with 3.0 V6 and the A610 transmission) that often shimmies at 35 mph. It starts at about 33 mph, peaks at 35, and tapers off at about 37 mph. It happens only when accelerating or to a much lesser extent when holding a steady speed at 35, but never any shimmy at all when coasting.
Sometimes, it doesn't shimmy even when accelerating. Whether the motor and transmission is cold or hot seems to make no difference.
At 35 mph, when accelerating, it can be a very noticeable vibration. The whole front of the vehicle shakes side to side and you feel it in the seat even more than the steering wheel.
I'm thinking this is most likely a CV joint, am I probably right? Or is this a symptom of "transmission shudder" and if so is it a symptom of an imminent transmission failure?
I have a Haynes manual, in the troubleshooting section it suggests "CV joint angle" as a possible cause, but after reading the CV chapter I see no information about setting or even checking CV joint angle.
There is a procedure to check the length of the CV shaft (and adjust by sots in the motor mounts) but after reading it a couple of times I see no mention that this is an angle adjustment. Is setting the length the same as setting the angle?