Frame vibration at 30-35 mph and again at 60-70 mph newer tires balanced and re balanced, started several thousand miles after tire change to Michelin ltx's 2000 tacoma 4x4 91,000 miles

put tires from rear up front and front to rear and see if tires cause a shake also make sure no debris on hub so rim sits flush if no change and still vibration check drive shaft and u joints

Most likely a tire/wheel balance issue. The weights that are used to balance the tires can sometimes fall off. Generally how far out of balance it is determines when and how bad it will shake. Unfortunately this is not fixable without a tire balancing machine, has to got to a tire shop.

Were the tires rotated or replaced recently? Most major tire shops will check the balance for you at little or no charge if you take it back to the shop where the work was done.

You can also try to identify the problem tire by rotating the front and rear tires one side at a time. For example, if the vibration is coming from the front, swap the front and rear passenger side tires and drive the vehicle again. If the vibration moves to the back it's most likely the (now) passenger side rear tire that's out of balance. If the is no change, try the driver's side tires.

Hope this helps!

If you jack up 1 wheel off the ground and put the car in gear , you can watch the tire spin. You might see a bent rim. The shop that mounted the tires should have seen it and warned you though.

These may not be your problems since it is occurring even at low speed but you might have the car just free of the ground and rotate each wheel and watch the clearance while you do it for changing clearance. This will reveal 'out-of-round' tires; it happens. Second; but less likely, I had this annoying problem of two speed ranges, around the 30 MPH and 70 MPH points causing wheel shake and it only stopped after I tossed the original brake rotors and replaced them with Brembos.
In 50+ years of driving, poor tires have happened several times and brake rotors twice. There was a feature of a now-defunct chain called 4-Day Tires that kept me going back called 'tire matching.' All replaced tires were checked and then shaved slightly to correct for roundness. With this done, I never had any loss of balance during the life of the tires. Haven't found this offered anywhere else since then; too bad.

Generally, the tire vibration only arrives at 60ish.
However, if you have a distorted tire, or worse, more than one, or even worse, Buckled Wheels!
You are inevitably going to experience vibrations, at varying speeds.
Take the wheels off, and make sure, the wheels are actually still,, er, circular.
It's best to put them on a Balancing Machine, then you can see how bad they are.
If the problem isn't solved soon, you may well be finding yourself, forking out for new wheel bearings.
That should do it.
Happy motoring.
Oh, & Don't forget to rate:))

check cab to chasis mounting rubbers.
can remove one or two bolts and see if change in vibration

Most computer controlled tire balancing machines which are in use today only balance tires to between 65/70 miles an hour. To get them balanced to a higher speed you might want to call a few auto performance shops and see if they balance tires to a higher speed. At higher speeds it takes very little in the way of an off balanced tire to really set up a vibration so shake.

bigc

Tires would be the 1st place to check. If you seem to feel it more in your legs then it is likely the front, if felt more in seat bottom then could be a rear tire. Depending on how severe the vibration is there could be a tire developing a tread seperation and should be checked right away. A simple balance of the tire and wheel assemblies may be all that required also but when on a balancer they should be able to tell if the tire has a more severe problem.
Driveline components could cause vibrations also however if the above sounds like it fits then check that 1st.

I had similar problem with my '99 outback. Replaced the front half shafts and seemed much better. A few months later seemed to be comming back so replaced the driver side shaft again and the problem disappeared. I had put in rebuilt shafts and the driver side shaft was not rebuilt correctly.

your car needs to be aligned and balanced...