Noob 89 k5

[fin & feather]

New to the site and thanks for all the great info posted here.
A little history about the truck. Re-furbished by the former GM at Dale Earnhardt Chevy here in NC for his grandson...extensive work on cosmetics, going over engine and electronics, drive train, etc. performed at the dealership 5+ years ago. All work done for grandson to drive thru college. After graduation (and a new Tahoe) Blazer was for sale and I bought it for OBX/hunt/fish mobile early '08. After layoff in Jan., and no more company car, now is my daily driver for 60 mile round trip commute (and hunting fishing truck). A few months ago lost the transmission on the way back from Greensboro...at an exit with a transmission shop. Rebuild tranny, replace seals on transfer case that were leaking and we're good to go...BUT. Now have a vibration that I can't swear started immediately after the re-build but definitely wasn't there before. I've replaced the u-joints, rotated and balanced the tires. Next thought is bent driveshaft (which I see no evidence of) or something amiss in the front end...or engine / tranny mounts? Vibration is most noticeable over 60 mph and no other ryhme or reason. Straight travel, curves on the interstate, doesn't seem to matter but definitely noticeable over 60. Weird part is it seems cyclical...no a constant shake but vibrates a few seconds, pauses, vibrates again and so on.
Any thoughts appreciated I'm at my wits end. I'm going to try something I read on the other section of the forum about jacking up one side of the front end and looking for play in the tire/wheel tomorrow, but that's about all I got.
Any other suggestions greatly appreciated and again, thanks for all the previously posted info. I grew up in a '74 and an '82 that my dad had so I'm really jacked about the truck, just need to reel this vibration in before it flies apart!
Can't post pic thru photobucket of the truck until 15 posts?? but will as soon as I can. Any way around this?

Thanks for any help you guys can provide!

 

[Teck]

Check all the ball joint when you check the wheel bearings.
Also check the transfar case mount

 

[fin & feather]

Thanks will check bearings and ball joints. Transfer mount okay from what I can tell.

 

[Teck]

I have seen drive shafts that don't get put back in the same place they came out , then vibrate. They may need to be turned or rebalanced.

 

[fin & feather]

Thanks Teck-
That's what I had planned for my next step that cost $. I've heard that they don't get seated proper and cause vibration rather than getting bent. I doesn't feel like the shake is in the front of the truck which makes me think not steering related. And it would be too much coincidence for the vibe to start right after the tranny work and not be related to the drivetrain imo. But I'm a carpenter, what do I know...

 

[Teck]

Also check the motor mounts, some guy have had that cause a vibration. If they let the motor just hang while the tranny was out, could have damaged them if they were weak before this.

 

[fin & feather]

Dumb question- how do you check the motor mounts?
One garage I took it to wanted to replace u-joints (which I had done), motor mounts, transfer case mount...kind of a shotgun approach with my wallet. And I got the feeling they didn't have any more idea than I did what was wrong and were just trying to hit on something.

 

[Teck]

Look at them close to see what kind of shape they are in. If the motor mounts look worn or broke down you will probably see this in the rubber. Some time you can stick a big pry bar in them and see if you get much movement, should be pretty soild.

 

[Teck]

Is the transfar case been lowered, spacers between the crossmember and the frame.
Could of had something that the tranny shop did not put back. Check the angles on the driveshaft, they should be close to the same.