A dull thud from underneath.

Hi all. I recently bought 07 Auto and when I stop in traffic i get a dull thud coming from underneath. It's coming from the transmission, driveshaft, rear diff area, and is driving me nuts. The sound is like a something of size sitting back in a housing or a mount or shaft slipping back, (and sometimes forward). Not a bad sound but somethings loose. I've re-done the brakes and that didn't change anything except better brakes.
Also the part doesn't do it after driving for a decent while.
Any ideas?

 

Rear Axle Wrap ??

 

axle wrap.... are you a 4x4? if so lube your slip joint

 

Yep, Normal..... I get it in my 2012 V6 auto.... Dealer tech said it was transmission, but slight axle wrap seems more like it.

Jesse

 

Ok I've never heard of axle wrap but will research it on the site. I'll check the slip joint too.
It seems to be after i've come to a stop and then the thud happens. It is a 4x4 and I haven't used that much yet. I thought transfer, or tranny mounts, driveline, or u joint but i will look into the axle wrap first.
thanks for everyone's help.

 

I believe what you are hearing/feeling is the release of tension (brake pedeal is probably pressed lightly) of the springs (decceleration axle wrap)... the spring wrap is "un-winding" so to speak.
A few pics to explain - these show acceleration axle wrap:

 

You have the classic symptom of axle wrap my friend. Lucky you too, my 2012 had it BRAND NEW. AND it came factory with a TSB leaf pack! (4 springs instead of 3)

AAL, traction bar, SUA (spring under axle), or a new beefier leaf spring pack will alleviate the issue. Take your pick as to how you want to remedy the issue.

 

That sounds like the slip joint needs grease replenishment. Unfortunately you'll have to remove the driveshaft to do this, as there isn't a zerk fitting for the slip joint.

Make sure the U-bolts are tight. Some are finger-loose from the factory or have worked themselves loose over time (due to leaf pack compression). Take a torque wrench set to 74 ft-lbs and give each U-bolt nut a tug.

If you go off road, keep in mind any kind of added traction bar, helper springs, etc. will restrict rear suspension travel. A thicker, more progressive leaf pack with, say, 9 leafs will reduce axle wrap somewhat.