Why does my truck shake when coming to a stop?

[Flyawayclyde]

So I just replaced the Harmonic Dampener on my 2007, 5.9 2500 4x4 Megacab. I have 146147 miles on it. Have had the truck since new.....
The harmonic dampener fixed the bad idle and the only just started to notice bad vibration from the front end.
So all is good there again!!
I also forgot to list that I have overload Leif's and airbags installed on the rearend
So As I am coming to a stop, under 15MPH or so. I am feeling a very noticeable "shake/vibration" coming from under the bed/rear-end. Honestly it does not feel like the brake system.?? I am suspecting the 'u-joints'.
does anyone here know what the service life is on the OEM u-joints?
Or does anyone have another idea as to the probable cause of my symptoms?

 

[AH64ID]

I replaced my rear drive shaft before 90K miles and the joints were worn but not toast.

It’s not out of line for your u-joints to be shot.

 

[Flyawayclyde]

That is what I was thinking too.

 

[Darkbloodmon]

Coast too a stop to isolate the brakes. Simple stuff first.

I installed new AAM sealed joints on my shaft, fingers crossed. Previous joints weren't OEM on my 03 my rear was a Moog greaseable from the previous owner but the front may have been OEM AAM.