Vibrations when driving

[IZ1111]

Hello, I'm having a problem with my car suddenly starting to vibrate strongly while around the 45mph area and also above 70mph its when it gets roughly strong. I think it all started when I changed my driveshaft to an aluminum one. The acceleration is buch better and the perfomance is great. But I dont know if this actualy effected anything. I haven't done an trans or axle oil change in like a year, so a simple mantainance could fix it. Does anyone know what could be the cause of the vibrations.

[G.A.S.]

You answered your own question.
If you just did a drive shaft change, there is something not right there.
A bad U-Joint will cause odd vibrations at various speeds and also be intermittent or surge.
You eather have a needel bearing that fell into the cap when you were installing them, A snap ring not locked in place or missing,OR, On the rear yoke some U-Joints require you to put a snap ring on the cap to keep the joint in line with the rear yoke. check the rear yoke for (ears) . if a snapring is not required then the yoke will have (ears). Make sure one is not broke off.
Are the bolts tight and the joint in line properly
check your pinion bearing as well.
When you installed the U-Joints, did you have a hard time getting any snaprings in place?
check your tire pressure or a tire problem.

[IZ1111]

Thanks for the advice, I'll see if I can get down there and check on all of that. I should have a responce to how it all turned out.