Hello Everyone,
I have a '68 DeVille and lately I've noticed a grinding noise coming from the rear of the car when turning a corner. It only happens when I turn right, and it's more pronounced when turning and going up an incline, such as pulling into a driveway. Does anyone have any idea what could be causing this? Thanks.
Wes
Tough to diagnose noises remotely, barring something like the exhaust hitting the body or more likely the driveshaft, could be an axle beaing.
Could be the drum brakes. When turning the side load moves the wheels very slightly and could cause parts not usually in contact to grind. Also could be differential gears, driveshaft bumping something, exhaust bumping something, etc.
-mB
Like Dave I'd go with axle bearings.
If you have a limited slip also called posi-trac differential you must add a friction modifier to the oil to keep it from making noise.
The additive loses it's effectiveness over time. If you have this type of rear end, change the oil and replace the additive.
DON"T let the fast lube places change the oil. They will tell you they have oil that either has the additive in it or doesn't need it, BS.
Good parts stores carry it, even Autozone. About 4 oz will do it.
I'd pull the other brake drum just to be sure it is not telegraphing to the other side. If no luck there could be the diff. Harry
I agree with S Passmore that it could very likely be a rear axle bearing.
Mileage might be helpful and history too. If you do not have "controlled differential" (limited slip/posi and etc.) then we can rule that out, but if you do it is something to strongly consider. I think if you have this option their is a sticker in the trunk explaining it, certainly VIN would let you know.
I do not think the vin shows what type of diff you have.
When a posi-traction differential was put on the car, didn't they have a metal
tag on the "pumpkin" that stated so? I remember GM did that on Chevy's so
I expect Caddy would have also.
Mike
For 1973 there will be a "G" in front of the ratio code stamped on the front of the differential if it has a controlled differential. We might be able to assume it is the same for a '68, it is in the shop manual.
If it DOES have a controlled differential, I am with Fred Pennington.
If you can jack up the rear turn one wheel forward the other wheel will also go forward if controlled diff is in place.
One way of checking for a bad axle race is to drive turning left then right, and loading up the suspect bearing.
Most every time, the bad bearing will be the one that is under the most load.
Bruce. >:D
I'll check if I have a controlled differential, and then change the oil. I haven't done that since I've owned the car, which has been 14 years now. So it's probably a good idea anyway. Do the 68's have a differential gasket, or do you just use the Permetex stuff?
Thanks,
Wes
You will need a special oil if it is a posi, so find out first. Easy way to tell jack up rear of car (both wheels).
The oil fill plug on a 68 will have a special tag indicating it is a controlled differential. The ratio code will also have a 'G' in front of the number. If it is a controlled differential make sure to get the special additive. I have 4 68s & 3 are the controlled differential marked as I mention. The shop manual verifies the information. Larry