Im not a great mechanic, but from reading the HAYNES manual, A loud grumble is cause for new driveshaft bearings.
Heres the update. The shaking started a little in other gears, and 4th gear is shaking harder. So last night i was coming home and right as i was pulling into my driveway, i heard a loud CLANK. So i started slowly going in reverse and 2 seconds later i hear the CLANK noise again.
My friend looked under the truck as i slowly moved foward and back and he noticed the clank nosie happend where the driveshaft meets the rear pinion flange.
I just took the rear pinion off last week to replace the seal. Im pretty sure i put the alignment back in the same order.
Are my rear differntial bearings shot??