Vibration in rear at certain speeds

[jesse_e30]

Ok, so I get this vibration that feels like its coming from the rear. I only feel it at 65mph and above 85mph. Now I know it cant be me driveshaft or CSB or guibo cause those are all brand new. And I thought it might have been my rear tires caus they were worn down to the steel belting, so I replaced those, and it helped out a lot, which means the vibration isn't as bad as it was but its still there. Any ideas? and only at those speeds any other speed is smooth

[Bglad]

Tire balance. I had the same issue. You may need a road force balance.

[jlevie]

A vibration that comes and goes at various speeds will be out of round or out of balance tires. Worn shocks or suspension will aggravate minor tire problems.

[mathillois]

i have a slight vibration going 25-28mpg from the mid rear and i did the cbs and guibo. any ideas?

[jesse_e30]

Tire balance. I had the same issue. You may need a road force balance.

I just had all tires re-balanced when I replaced the rear tires

[jesse_e30]

A vibration that comes and goes at various speeds will be out of round or out of balance tires. Worn shocks or suspension will aggravate minor tire problems.

My Billy sports only have about 2k miles on them

[jesse_e30]

maybe worn bushings? I know these need replacing soon

[Sea Aych]

i have a slight vibration going 25-28mpg from the mid rear and i did the cbs and guibo. any ideas?

I have a very similar issue to you, going an (indicated) 60-80kph. Do you get a droning noise too?
Check your half axle shafts for play. My rear left one has very slight play and i think it's causing my problem.
Check your u-joints on your driveshaft.
Bad alignment can cause slight vibrations too (although that's pretty obvious to notice if you need an alignment...)

Jesse_e30, you could probably check those too!