Hey guys Im running out of ideas. First off the issue: As i'm driving my 1981 with 33" on pavement in 2wd i can here a "thunking" sound from the rear. The sound is directly proportional to the wheel spin(as i go faster the thunking sound gets faster too). I do not have to be in gear to hear it(its actually easier to hear it when i just throw it in neutral and cruise). If i lift the back tires off the ground and put it into gear there is no sound. So far i have replaced the Ujoints, lubed up the yokes, changed both rear axle bearings/seals/brakes and still making the sound. I still have the stock gears(as far as i know) which are 3.90s which yes i know are low but havent had a chance to change them out since i have been working on this issue. My buddy walking beside the truck as it crawls along says it sounds like it is coming from the diff. Any thoughts? gears?

Thanks in advance

 

Have you looked real close at your tires for a bubble or a flat spot .

When you had the axles out you should have pulled the rear all the hard work was done.

Rears for the most whine and scream not much for thumping but who knows

 

The pinion nut can back off with time.


If so how was the third member when you pulled it to check/replace the rear bearing seals/ bearings?

 

I have looked at the tires very closely but i was still going to swap the fronts to backs to see if it changes anything... As for the 3rd member we havent gotten that far yet... i plan to open it up after the weekend and take a peek inside.

 

GOOD NEWS!! the issue was a busted off bolt head inside the brake drum that lead to the new bearing to go asap... The bolt head came off of the plate the holds the park brake on(which was really weird because we didnt take that apart when rebuilding it) so had a new bear and seals ordered up ASAP and noise is gone. Thanks for the help guys... now time to move on with the project