67 rear noise

[Rex T.]

Just took my new 67 out for a spin this evening and there is a very noticeable popping / jerking noise as I make a left hand turn. Am I safe to assume this is the posi-trac unit / clutches needing attention, or could it be a rear wheel bearing? If it is the posi unit, I have heard of people draining the rear end grease and filling it with some type of cleaner (kerosene???), then running it around in circles for a few times, draining this and then refilling with posi lube and it cured the problem. Anyone's thoughts? As always, thanks in advance for your help.

Rex

[Donald M.]

Re: 67 rear noise

Rex, Judging from your description, it does sound like posi noise.However, all you need do is to drive the car to warm up the existing fluid and then suction it out and replace it with fresh posi-lube and add a small bottle of GM limited slip lubricant ("whale oil" to us old guys)I don't know the GM #, but I'm sure others will weigh in on that. Then drive figure eights, not circles, in a parking lot to work the additive into the clutch packs.
Don

[Roy B.]

Re: 67 rear noise

Or could be a U-joint, it will also make the same sound

[Mike McKown]

so will a tooth knocked off a spider/axle gear *NM*

[Joe C.]

Re: 67 rear noise

Rex,

Assume that you have no prior knowledge of your "new" 1967 Corvette. Assume that your diff lube may have been changed at some point, without sufficient friction modifyer added. Assume that universal joints are serviceable. Normally, one four ounce tube is required for proper diff clutch operation. Friction modifyer usually comes in four ounce tubes, and you don't have to use GM (expensive) product, as any product will do the job. Drain and fill your diff with fresh lube. Leave enough room for two tubes (4 oz. each) friction modifyer. Start by adding 4 oz, then do the figure eights. If still chattering add 2 more ounces, figure eights. Still chatters? Add the final 2 ounces, for a max of 8 ounces. Still chatters, replace clutches.