Your slip yoke is leaking and throwing fluid on the muffler in the pic. That is an indication that you are putting pressure on that seal. Which means you are putting pressure on the shaft in the T case causing your vibrations. With a 4" lift you need a SYE and a CV drive shaft. I had vibrations until I bought mine and put it in. CJ Tatton is on Ebay and has a store. He sells a combo kit for $460 with shipping. It is easy to do and eliminates your vibrations. Plus the SYE won't leave you stranded in the middle of nowhere. Hope this helps.