I have a new issue that has me baffled... I have replaced every bit of the front end of my truck with new, I have new Rancho 5000's all the way around, I have replaced everything including drums on the rear end for brakes. been running and driving great, this week, all the sudden, if you are driving above 55 mph and hit a large expansion joint or pothole with the rear of the truck, it immediately feels as though you have blown a rear tire due to the violent vibration. You can hit the brakes and drop the speed down to 45-50 mph and it smooths back out. This has happened 4 times this week. I can get it all the way up to 75-80 and it stays smooth as glass, but any moderate bump to the rear makes it shake so bad the Guys on the radio start to stutter... I can't find anything that looks out of the norm, it has new tires on it with maybe 1500 miles on them. The rear shocks are new, I have no play in the driveshaft, the leaf spring bushings are dried and have some fine cracks in them but don't look terrible, the u-bolts are tight...I'm at a loss and help would be greatly appreciated
it's a 89 4wd automatic short bed 4.0
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