Here's one for the experts; My 66 Electra has a very pronounced drone with a bit of a vibration between 65-80 mph. At 80 it either changes pitch or goes away, can't be sure which, that speed is loud in a convertible regardless. So here's the problem; - I had all the U-joints replaced, and the CV joint and steady bearing checked, which I was told it was "okay". The rear axle is a posi unit, I believe a 3.07. I had it opened up as well, and they told me the clutches weren't in the best of shape anymore and it'll need a rebuild "soon", but it was still "serviceable". Okay, considering the past history of this car, I can see that. It was very abused prior to when I got it. The other thing I know about the car was that at one point in it's life it had been hit in the right rear quarter just behind the door. Looking at the frame, there doesn't seem to be any evidence of stretching or creasing, leading me to believe it wasn't bent. Now, if I'm doing 70 or so in the left-hand lane, the noise and vibration is more pronounced. It only seems to be there at cruise and deceleration, not at acceleration. Feeling the floor along the tunnel there is no pronounced banging or vibration evident, it feels exactly the same all through out, solid and cool, no heat. With the top down, can't hear or feel a thing out of the ordinary, so I don't know... The questions; - Is it the axle or the diff? Is the steady-bearing or the CV joint? Does the crossmember holding the steady bearing in float? Or is it bolted to the frame? Are there supposed to be rubber grommets where it comes into contact with the frame? One thing about the axle (I think) is that it clunks when turning to the left. At very slow speeds, (creeping) towards the left, it clunks like the driveshaft is binding up. Also, the car just completed a 1000 mile round trip through the Rockies, the vibrations or drones and clunks haven't gotten any worse, it performs exactly as it did before the trip. And to eliminate other issues, both the transmission and the motor were both completely rebuilt and new mounts installed. The original mount on the tranny had screwed up and the housing was cracked. It was welded up and it is holding I was assured that the tailshaft wasn't bent either.
You need to add 1 or 2 bottles of GM posi lube to the rear end oil. I usually/preferably use 2. After it thourghly mixes with the rear end oil & gets between the posi clutches the clunking will stop. Almost guaranteed the driveshaft/pinion angle needs to be adjusted for the drone.
The clunking sound you get while cornering is the posi unit itself.If there is NOT one bottle of additive in it already,then add one.You do not need two. This is a fairly common characteristic of posi units. If anyone has been down the highway for an extended period of time,then got off,you usually get it when turning off the off-ramp. The posi unit itself does not have anything to do with the droning sound or vibration that you are getting while cruising. It could be a sign of a bearing going bad.When you say it is more noticeable at cruise or coast,and not acceleration,tells me that it might be a pinion bearing,or something related,that would possibly cause the pinion to move in & away from the ring gear.The fact that your car had previous damage might indicate that you could have a bent axle shaft or bent axle housing.You could remove each shaft,check those axle bearings,and put the shaft on a lathe,to dpin & check for straightness.Even the slightest bend can result in a vibration.If the wheel itself was hit when the car was damaged,then the wheel flange on the axle shaft might be out of true.I would focus more on the side that was damaged in the wreck.
Hi Brian- on the big car rear ends they take a little more fluid, necesitating the xtra bottle of stink juice. Spot on for other issue, now I do not have to type :TU:
Thanks for the advice fellas, I will be getting some of that stuff and loading it in. Sounds like you guys nailed the problem, the diff clunks exactly as described. I guess I'll schedule that rebuild for this upcoming winter. As for the drone; - I wish I could describe it better, I'm familiar with the usual worn out axle growl and drone, this is different. This sounds like a shaft that is out-of-round. It's a vibration, but a constant one, I'm thinking that the accident may have caused the tailshaft to bend throwing the front yoke out of line. But there are no tranny fluid leaks, and the steady bearing looks old but essentially fine. I'll try and find a shop that has the facilities to spin the whole works up, I think that may be the only way I'm going to find it. Yes, I've also considered that the car could be bent. An uncorrected bend would cause the whole works to run out of round; - but the eventual end would be that it would tear itself apart. I thought for sure on this trip I would leave chunks of driveshaft all over the highway in a passing manoeuver but it never happened. The car accelerated quietly and quickly up hills on the passing lanes, and on a few it topped 100 mph. That's why this is so disconcerting and puzzling, it should have come apart and yet it hasn't changed one iota. Maybe it is all in the axle after all...I'll get it checked out.
LIMITED SLIP IS ADDED IN A % TO THE SIZE OF THE REAR. GM sells the Stink Juice in 4oz bottle Usually sufficient for all 10 -12 bolt applications where 2-2.25 quarts are used. Some stores sell it in 6oz. bottles too. so just say one or 2 bottle is not a good enough answer...oz. would be better answer. MORE usually will not hurt anything your just wasting money. Sometimes if the unit is old there will be NO amount of additive to help out this effect as it is the clutches getting smooth from wearing to each other and the clutches will suction to each other. In this situation A massive amount of torsion is needed to break the clutch pack loose, then it sticks again and violently releases and sticks again until the turn is completed.... hence your chatter. Sometimes replacing the clutch pack may be the only remedy. AN over also be cause by excessive amount of clutch pack preload also (example 800# springs installed) Drive line drone. Brian is about narrowed that down... Double check thing you can before going all the way in the rear. U-joint, drive line angle from one u-joint to the other. pinion NUT loose that hold the yoke in place...THERE SHOULD BE zero in out or up down pinion movement....only twisting. Good luck guys... J D JIM
