I have an 05 Odyssey that has a steering wheel shimmy around 70-75. it comes and on 2005 Honda Odyssey

I have an 05 Odyssey that has a steering wheel shimmy around 70-75. it comes and goes at those speeds. comes on slowly and builds then goes away after about 20-25 min. comes back 30 minutes later???
sometimes is more pronounced when engine is under power. sometimes shimmies at 65 when engine is coasting???
Have changed tires and had them balanced, also had torque converter changed because of grind at 40-45.
Any ideas.

Asked by for the 2005 Honda Odyssey
Have the passenger side axle assembly inspected. It's 2 pieces-intermediate shaft and axle shaft. The splines where they connect can wear and cause seperation(gradual). ANY signs of the inboard joint moving in or out on the splines of the intermediate shaft would be a good cause for replacing BOTH. (don't do one without the other!).Good luck.
Thank you,
What has been very confusing is why the shimmy comes and goes. Would and axle wear problem cause that??
On that particular setup I have seen at least a 1/2 dozen different types of symptoms , all with 'mysterious vibration/wobble and each vehicle has had its' own particular speed or other driving condition that would agravate it. Some were low speed under load others on turns and some like yours , at higher speeds. Only two of the cases I had , I was able to duplicate the symptom on a lift running it up to 65-70 MPH.---hint to aftermarket tech.- disable VSC or TRAC while in drive with brake on - when in drive and engine speed is up to 2500 RPM then quickly put in neutral and back in drive , so it will shift to higher gears.