hookemdevils22

iTrader: (12)

I've got a good vibration above about 65 in my 8.5" 10 bolt. It has resulted in false brinelling of the axles' outside wheel bearing races (see pic below) and backed the pinion nut off at least once.

The car is a '71 Nova with an LS and 4L80e. The rear has 3.90s and an Eaton posi unit, and is not original to the car. I'm pretty sure it has been present since I had the rear installed, though I didn't get above 60 much before swapping in the LS and 4L80e.

The engine, trans, wheels/tires, and drive shaft were replaced when I did the swap, and the drive shaft has been double-checked for balance. The driveline angle has also been double-checked, and revving the engine in neutral does not introduce a vibe.

I just had the axles out and took some photos. Does the gear pattern show anything, and what else should I be looking for? Also, I'm in Phoenix, so any recommendations for a good shop NOT on the West side would be greatly appreciated.











And the false brinelling on the axle

-TheBandit-

iTrader: (1)

Put some gear marking paint on it and run a pattern.
Measure the back lash with a dial indicator.
Check for play in the bearings.

-TheBandit-

iTrader: (1)

Most vibes can be traced to the u-joints and their operating angles. It's not often you'll get a vibe from the differential itself.

therabidweasel

iTrader: (5)

Im not good with patterns, but to my dumb eyes the coast side does look shallow...drive side may be a little shallow too. But, do not go by my word...I wouldnt.

Backing off the pinion nut sounds like one hell of a vibration. Have you checked the runout of the axle flanges etc? If you put it up on stands does it still vibe, if yes does it still vibe with no wheels? If it vibess with the suspension loaded and no wheels and not reving in neutral its the ds, yoke, or rear...right?

-TheBandit-

iTrader: (1)

Does this rear use a crush sleeve? If so how did you tighten the pinion after it backed off?

-TheBandit-

iTrader: (1)

Are your joints phased properly? The c on each end of the shaft should be aligned.

hookemdevils22

iTrader: (12)

I'll double-check the u-joints and driveline angle. It's fairly easy to manipulate angles with the rear. I'm also going to get it up while on jack stands with the axle supported and unsupported to see if it affects vibration.

Pinion nut was re-torqued when they checked the drive shaft. It and the crush sleeve was reused (I know, bad...).

hookemdevils22

iTrader: (12)

I checked pinion and driveline angles last week, but didn't check the driveshaft, so I'm not sure how the angles were vs. the shaft. Due to the fact that the vibe seems to go away upon acceleration, I moved the pinion upwards one full turn of the ladder bar adjusters (didn't check angle thereafter). I haven't driven it since (I get only a half-hour here and there due to the kids and my wife hating me working on the cars), but did get it up to ~65 with the frame on jack stands and the rear axle drooping. It still vibrated.

I also can't find any markings on the u-joints to sync them. I'll try to take it out on the highway tonight.

lees02WS6

iTrader: (5)

"syncing" the u-joints would only be necessary if you get the yokes out phase with each other. You'd need to have a shaft with the slip yoke in between the shaft and the u-joint (see image), as opposed to having the slip yoke insert directly on to the trans output shaft, to have them get out of phase.

hookemdevils22

iTrader: (12)

Thanks for the info. Still have high-frequency vibes on the highway. I'll pull the wheels and check runouts at both the pinion yoke and axles. And I need to better check the driveline angles.

hookemdevils22

iTrader: (12)

I broke down and took it to a shop near work. They found the pinion bearing bad (said it was likely due to overtightening). They said they could open it up, but that it would probably open up a can of worms, so I'm going to hold off for now.

Oh, and the driveshaft was twisted. Which is bad, but also pretty awesome?