I have a 1989 K-5 Blazer with a 700R4 and 241 transfer case. I put a 4 inch lift and did a shackel flip to ease the bind on the drive line. After doing the shackel flip I have a bad vibration and a noise that sounds like gears are lose when I back out of the throttle. At 20 miles per hour the vibration is at its worse. It shakes the whole truck. I replaced the rear drive line and U joints and rear end and it is still the same vibration. I thought it was the transfer case, so I bought one and still no change. The vibration lessens when I put it in neutral. I am at a loss and can't figure it out. Could it be the transmission?

 

could be the angles, the angel of the t-case and pinion should be the same

 

bump on a tire?

I was going down I64 one day at speed with no issues. We slowed down as the traffic built up either going south or north on I81 at Staunton and when we got down to about 15 or 20 mph it felt like the back of the Blazer was tap dancing.

Pulled over then and there but couldn't see anything. Stopped in Staunton, at the WalMart parking lot, got out and let the wife drive it forward/backward while I watched. Then it was obvious the left rear tire was bouncing. After some slow rotatation and close looking I could see a "bubble" under the tread (leak between the layers for some reason).

Had to buy two new tires (that was another reason I stopped buying BFG tires - went through several of them in the first 3 or 4 years I owned that K5).

Take a close look at your tires. Might not be an issue but with mine I couldn't feel it at highway speeds, just when going slow.

 

This ^. And did you just flip the shackle on the truck already or did you buy the correct kit? I personally dont like the looks of those kits and think that could be an issue too.

 

How do you do this?

We did the shackle flip ourselves.

 

I ran into this problem on both of my K5's that I lifted. What I did was angle the rear toward the t case output just like running a SYE with a CV shaft and it cured the problem for the most part. And no the flip kits don't cause any issues.

This is with 4" Tuff Country EZ Ride rears.



This is with a ORD Flip, 6" shackles, and 56" rear springs. It flexed better and rode better both on the street and trail.

 

SO you flipped the stock shackle or bought the correct ones? And i checked this out in the past and asked others who have done it and its about 50/50 on the quality afterwards.

 

Thank you fixed it.

 

I lowered the trans cross member 1 in and no vibration.Thanks for all the info I was going crazy.

 

If you plan to wheel it then I wouldn't lower the t case. Save your $$$ and get a SYE and CV shaft. It's also easier on u joints. My rear shaft has been running the same U joints for 10 years with no issues.