GX470 Drivetrain harmonic related to diff brackets

[SOTF]

I am aware of the TSB (http://www.alflash.com.ua/avtovideo/2005l/L-DL001-08.pdf) that changed parts out including the transfer case portion. My 04' gx470 either came with the fixes or they were completed as the dampers are installed on the diff + t case. When I purchased it used the top washer/stopper with the rubber attached to the top driver's side bracket was missing. The piece that sandwiches between the bracket and diff. I didn't think much of it and I installed poly bushings into the brackets stupidly thinking it was an upgrade or decent replacement. I've had the harmonic and vibration between 50ish and 70-75 only when accelerating (WHIRR... WHIRR...WHIRR) below the driver seat and I am assuming it's the poly bushings not playing nice with this vehicle. I question why the dealer had removed that piece, there was no harmonic on a test drive, which makes me think the harmonic was present even with the OEM bushing so it was removed to sell but I digress. My question is: Does anyone use poly bushings on the diff mounts on these vehicles and not have a harmonic upon accelerating 50-75? Nice vehicle but Jesus that sound is annoying and the vibration sucks too.

 

[fvedmo]

Ugh, I hadn't seen this TSB - I definitely get a wub wub wub harmonic around 65-70mph