4.10's with 3.5" driveshaft

[MarkVIIIS]

A year ago I had 4.10's installed with a traction lock diff and a 3.5" dynotech driveshaft. I bought the driveshaft from Dennis Reinhart he told me that it would be all I need. I had a vibration from about 80MPH and higher with everything stock but ever since then its been about the same maybe a little worse its been so long I don't really remember how bad it use to be. So my question is should I have gone with what the 4" which is what I was originally going to buy before he convinced me that I didn't need it.

 

[DLF]

I went with the 4", and you probably should have also.

Look at the tech doc from Mark Williams I posted in this thread that shows the critical speeds for various driveshaft size/material combos.

 

[MarkVIIIS]

Thanks I probably should have