Vibration source chasing

[Adamhach]

Hello all, I am new to this forum as I am at a loss for what to do and where to look next to find this vibration that has been persistent for about a year now. 2002 Silverado 1500 LS 4.8L 2WD 4L60E Extended cab 365,000 miles. The vibration feels like a paint shaker is in the cab at speeds anywhere between 35-45 mph and reappears around 65 mph. The vibration is present at acceleration and deceleration while in gear or in neutral. I've had the truck for around 7-8 years and this vibration ha developed within the last 1-2 years. Since the vibration has began I've replaced:

-Multiple tire balancing and rotations
-At least 2 alignments
-Both front wheel hubs with MOOG/Precision hubs
-Both rear wheel bearings and seals with Yukon gear bearings
-Both axles shafts with Yukon axles. The originals were well worn and pitted beyond repair.
-All 3 u-joints in the two piece drive shaft. Front u-joint with a Precision joint and the rear 2 joints are Spicer.
-Center carrier bearing with a Precision branded one.
-Both slip yokes have been cleaned and regreased.
-Transmission mount
-Both rear leaf spring sets have been replaced with new sets as the old ones were worn out and 'W' shaped.

I haven't touched the engine mounts, timing chain, harmonic balancer, the trans extension housing bushing, any of the ball joints/ a-arms, or tie rod ends.

The front end components appear to be tight despite most of the boots being busted on them. I can't get any in/out play from the tie rods and no up/down play from the ball joints. The control arms bushing aren't cracked from what I can see. As far as I can tell the a-arms assemblies, upper and lower, are original to the truck.

I feel a very slight vibration in the steering wheel when the vibration is at its worst at ~43 mph, but the vibration feels like it's coming from under the truck which I don't understand. I've attempted to move the pinion yoke to check for a bad pinion bearing, but the yoke appeared to be tight. I am unsure of the carrier bearings in the differential. The differential is original.

The engine and transmission are original to the truck as far as I know and have had regular fluid and filter changes since I've had it for the last 130,000 miles/7-8 years. The previous owners also kept it well maintained with regular changes, or so they say.

Any insight on what to do next would be greatly appreciated.

 

[bigdogYJ]

You seem to have attacked a lot of the typical and some not so typical reasons that would cause this. Chasing down chassis vibrations can be tricky. Do you have access to a lift to get the tires up off the ground and run it up to ~40 mph? Maybe have the hood popped to keep an eye on the motor to see if it’s moving at all? That would probably be my next step. Any noise associated with the vibration? I bought a set of chassis ears a number years back to track down a hum in my wife’s Yukon. Ended up being the planetary pinion set in the awd transfer case. the chassis ears helped me narrow it down. But it usually works with noise not just feel.

 

[ORVietVet]

IMO, I would pull the entire driveshaft assembly and have it checked and balanced and have them pay close attention to the splined area of the 2 shafts.

Had almost the same vibes at the same speed on my girl's 1990 K2500 and the problem was the rear driveshaft out of balance. Local shop, that I used to run, did the work.