Rear end noise and vibration

[carkrazy1987]

A little background.

05 gto. Built motor, auto. Rear axle swapped to solid axle. Chassis engineering 4 link.

8.6 rear axle from 07 trailblazer, narrowed to fit. New aftermarket axles. New axle bearings, new 1 piece driveshaft.

Vibration at 80-120mph. Almost like a flat tire. Has hard pull left when you drive thru the vibration.

First thing we did was put the car on a drive on lift, full weight on suspension, checkes drive line working angles, all within specs. We then rotatwd the drive shaft 180, just to try it. Road test, same thing.

Back on drive on lift, we lifted the rear axle, (suspension still loaded) and Removed rear wheels, and brought vehicle to speed on lift, rear axle vibrating, cant touch a single axle or suspension component that seems to vibrate more. Removed rear brakes and rotors, and retried, same results.

Removed driveshaft and rotated rear diff, felt like possible pinion over tighened, and felt abit of resistance in certain areas. Opened cover, found oil abit shiny, removed axles and diff. Inspectes bearings, no damage can be seen, everything spinning freely. Check axles for beaing visually bent, cannot visually see damge or bends. Checked pinion, still feel alil tight and rough. Removed pinion and inspected, no damage seen. Replaced both pinion bearings, and reassembled, 0.006 backlash, good contact pattern. Replace yoke and seal also while there. Retested on drive on, vibration seem to be gone.

Road tested, vibration moved up to 100mph. Back in shop, installed gm vibration Analysis /pico scope. Road test and shows first order drive line vibration.

Ordered new gears. Changed gear set for new summit gears, (summit gears noisy) set at .010 backlash, good contact pattern. Noisy at 60mph very loud on coast. Have not been able to make a full high speed pass, since final gear install.

Just looking to see if anyone may have any more ideas on what to look at.

[4mul8ion]

What about a bent axle shaft? Is there an even wear pattern on the axle shaft journal from the wheel bearing?

[carkrazy1987]

We checked for possible bent axles, we cannot see any damage. Bearing marks even on both sides. Whole setup has less then 100mi.