Good day
My dodge grand caravan 96 3.3 L was working perfect until yesterday when I had decided to change the transmission filter and fill with ATF+ 4 oil . At the same time I had decided to adjust the back wheel break .
Today at the highway when driving 100 km/h my car was vibrating and shaking so badly . The roads are very wet .
Could it be the transmission , or could it be the breaks adjusted so tight or because of the wet street.
Any advice- thanks

It could be warped rotors that need turning or the tires need to be balanced.Do not go to one of thse tire shops for one reason: They do not calibrate their tire machines since they use them a lot.I have seen vehicles come that need the tires rebalanced after one of those tire shops did them and were off a lot.

See this link (http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml) before you completely buy the argument of "warped rotors". Obviously it's an internet source, so credibility would be in question, so you'll have to be the judge of that.

Second of all, "warped rotors" typically only presents the vibration during braking, and the wording by the OP does not imply that the vibration was only occurring during braking.

When you adjusted up the rear brakes, how did you decide when they were tight enough? You spun the wheel on it while up in the air, right? I seem to recall that about 1/2 revolution after letting go was "tight enough", but really don't recall entirely. However you adjust it, make sure both sides are roughly the same.

It would seem to me that you'd have to have a *severe* mismatch in rear brake tightness in order to cause strong vibes, but I could be wrong. I'd be interested to hear what the pros have to say on this.

Has anyone heard of traction control systems going crazy on wet roads that could cause the kind of vibration the OP is experiencing?

My philosophy is to start simple and work towards the complicated. I am assuming you removed the rear tires to adjust the rear brakes. Could it be you knocked a balance weight or two off of the tires while working on it? Check your tire balance first, especially if vibration is constant. For that matter, you may have knocked a balance weight off one of the drums. That could cause the vibration, too. Double check your drums, as well (Of course, I am assuming rear drums, the most likely case in your application. If you have rear discs, disregard the drum advice.).

It could be a hard spot in the drums also.The only fix is to get the drums turned.