Rear rotor runout problem-now what?
Thread Starter
Instructor
Joined: Oct 2005
Posts: 113
Likes: 0
From: Melville, Long Island NY
Rear rotor runout problem-now what?
My 79 appears to be suffering from excessive rear rotor runout. Not sure exactly how bad, don't have a runout dial indicator. However, the runout is apparent by eye just watching the drive axles turning while up on jack stands.
Is there a temporary resolution for this problem? I will be rebuilding the rear and replacing the trailing arm assembly at some point in the future, but will be waiting for the body off resto to do that.
Thanks in advance for the suggestions. Tom
Is there a temporary resolution for this problem? I will be rebuilding the rear and replacing the trailing arm assembly at some point in the future, but will be waiting for the body off resto to do that.
Thanks in advance for the suggestions. Tom
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
If you are turning the rearend over while on jack stands the universals bind at one spot and cause the axle assembly to jump. At the very least you need to support the car so the trailing arms are at about ride height to prevent universal binding.
Never run the car with the trailing arms hanging down and the rear wheels spinning.
Never run the car with the trailing arms hanging down and the rear wheels spinning.
Pro
Joined: Jan 2005
Posts: 539
Likes: 3
From: Twin Cities Minnesota
I know they make shims that you can put under the studs between the axel and the rotor, but you should put a dial gauge to check the runout. It pretty easy to set something on the floor to attach a gauge to check the rotor.
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Originally Posted by 76project
I know they make shims that you can put under the studs between the axel and the rotor, but you should put a dial gauge to check the runout. It pretty easy to set something on the floor to attach a gauge to check the rotor.
You need the dial gage attached to the trailing arm, not the floor or anything else free standing. I place a piece of angle iron on the trailing arm and clamp it in place then use the magnetic base and dial gage to check rotor runout. You also need bearings in good condition. If you have .008 runnout on the bearings you will never get a good rotor reading. I try for .003 maximum runout including bearing free play.
Tech Contributor
Joined: Aug 1999
Posts: 15,179
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From: Connecticut, USA
Norval is correct, you have to be sure the arm doesn't move when using an indicator or you'll end up pulling your hair out!
I don;t know how far you are from New Haven CT but let me know if you need any help. I can walk you thorugh the job I'm just kind of beat tonight! Sorry I just finished up a couple of jobs and I'm heading home.
Gary
I don;t know how far you are from New Haven CT but let me know if you need any help. I can walk you thorugh the job I'm just kind of beat tonight! Sorry I just finished up a couple of jobs and I'm heading home.
Gary
Tech Contributor
Joined: Aug 1999
Posts: 15,179
Likes: 3,999
From: Connecticut, USA
