85 Suburban (I got a shudddder in the mudder - TH 700 R4 Problem?)

[Suburban85]

So I get this Black 85 Burban with far too many miles on it and a truck load (hee hee) of work to do.

1. I love the truck, I don't love the vibration at 55 mph!
(also, When I JUST synchronize engine speed with road speed, there's a loose rattle kinda like a U-joint)

I know it's not the U-joints(new and clean), I know it's not the alignment (new ball joints, Wheel barings),
I dont think there are any weights missing from the prop shaft, and I think the shaft is streight.

2. I love the truck, I dont love the shudder at part/full bore take off from stop!

I thought that this was a symptom of messed U-joints, but that's not it. Maybe rear gear (Ten Bolt 8 1/2")?
Maybe The Trans(TH 700 R4)?
I was told that a cracked flex plate could do these things to a poor half-ton truck like mine.

Please HELP!!!

I dont wanna kill my baby.

 

[jimmyjack]

When you check your u joint put the tranny in nuetral and try to shake it. Mine didnt move a bit until I checked it in nuetral. The yoke could have a groove in it too.

 

[Suburban85]

Done that