Gear Shift Knob Question?

Long-time reader, first time poster. The reason i'm posting is because I have a question that hopefully some of you guys that have done this can answer. I recently bought a new gear shift knob for my truck (AT) and it came with some set screws and some plastic adapters. The knob is meant for a 1/2 inch shaft, so granted, i used the adapter that was supposed fit best on the truck, but it doesn't thread on, it just slips over it. After you but the set screws in and even after you put the lower collar on, it still just sits on the shaft, basically you just lift it straight up off the shaft if you go to put it in drive.
So my question is, what is the best way to install it? Do you just crank down on the set screws until it goes through the plastic, do i need to buy a different adapter, or do i (hopefully not) need to do something like glue the adapter to the shaft?
Thanks in Advance

 

if the set screws have enough thread -tighten them thru the plastic -so its TIGHT.
You can always buy longer set screws!! Thats what I would do--not sure of your exact situation.
just my opinion-set screws should only cost a couple cents

 

Cool thanks, I'll try that

 

On mine, I just bought the right size nuts and put 3 on the shifter. I put the new knob on after that, tightened it down on the nuts, not the plastic adapter thing. Held solid, no wobble.

 

Do you remember what size nuts you bought? It seems to me that that would be like fitting a square peg in a round hole...

 

It's an auto, believe 8 x 1.25 They fit inside the "collar" on the knob just fine. get all nuts tightened together so none move. Set screws lock knob in place fine.