Vibration issue-needle bearing? Or something else

I have a 2016 TRD Off Road with a Four Wheel Camper (around 900 pounds) installed. The rear suspension upgraded to OME leafs and Nitro shocks, Firestone air bags with cradles. Now the issue:

On descents only, whether the truck is in auto, manual shift, or neutral, I have on about 8 occasions in a 12 month time period, experience a shudder, slow and slight steer to the left with nothing else happening. This has happened in all of the transmission situations listed above and the brakes were not engaged at any time during the experience. The severity of the experience has varied with the angle of descent. I have assumed that it was transmission prior to it happening while descending from Bunny Flat at Mt Shasta while in neutral (a test for this very problem). The truck shutters under the left side and I feel a halting as if the transmission is engaging in some way.

Up until the last event I had not modified the front suspension however I just installed OME coilovers (and don't expect this to have an effect either way). Anyone else experienced this or have a take?