Rear end/drive train knowledge?

S

sofa king

Forum Member
I’ve been having this issue for quite some time now.
When driving the car, say 60mph, cruise set and its freewheeling, there is a bad “banging” noise that I hear.
Seems like it may be the rear end.
Remove and checked, then reset the ring and pinion.
Backlash is 0.010”
Ring gear is torque to 95ft lbs
80W90 oil, added 4oz FMS friction modifier.

I can’t drive the car anymore, the banging is totally annoying.
Control arms ok, removed and inspected all bushing, torque boxes welded and ok.
Remove driveshaft, trans in 4th, engine off, output shaft is solid, minimal movement, no more than one would expect.

Car is on jacks, 4th gear, let clutch out and roll, no pedal.

Link to video:
[video]http://s277.photobucket.com/user/my8950/media/video/IMG_2508.mp4.html[/video]
 
Wild guess, could it be the rear brakes giving feedback. Pull the wheels and drums/discs. Wondering if the brakes could be dragging and giving backlash feedback in the drivetrain.
 
Razmiblackz28 said:
Wild guess, could it be the rear brakes giving feedback. Pull the wheels and drums/discs. Wondering if the brakes could be dragging and giving backlash feedback in the drivetrain.
Click to expand...

Also sounds like it could be the exhaust banging on something, but its hard to tell in the video.
 
Is the video working? I never posted video before, and if I click it I think it works, but I hosted it from my pc as well, I'm curious if anyone else sees it.
Anyhow...
Does this in any gear.
I can try taking the wheels and tires off, and even the rotors...Rear has disc now. Not sure how it could be brakes since it occurs while driving, but I wont rule it out until I take em all off and try it.
After I did the gear again last month, fired it up and check to see, same issue. Easiest next step was another drive shaft, same thing.
I'm curious about the "tune"....Cant rule this out either, but the car drives and runs ok, but it can be tweaked. Can you elaborate?

Thanks all, I'm really stuck with this one, aggravating the crap out of me, seems like 99% work 1% driving, getting stale.
 
my engine would surge at certain rpm's and the rear would start doing it.
When you changed the gear did you check the runout of the carrier?
 
By the way the nose of the diff jumps up and down almost right along with the noise I'd look for a binding U-joint, OR, are you sure it isn't a part of the exhaust hitting the bottom of the car, or rear frame rail somewhere?
 
Exhaust not hitting body, I swapped driveshaft to another but same issue.

Did not measure runout, I could do that, but the frequency of the banging is totally random, there's no pattern to it.
 
I am not convinced that it's in the rear end. To me it sounds like something is banging around more from harmonics than anything else (to me it sounds like exhaust). I think you have the right idea putting the car in the air and letting it run. Repeat that test again but this time use a mechanic stethoscope to isolate the issue. You will hear the noise loudest at the component that is banging. I think that you are hearing something that is just resonating making it sound like the rear end.
 
I would hope for something like exhaust banging.
The exhaust is painted black, so I can check again, for something banging like this, there would be dents or at least paint chipped away somewhere.

From my memory, it will go away while coasting, if I pop it into neutral I don't hear it.
The only time I hear it is while going at a steady state condition.
If I get up to 50 or 60, and just roll, keeping it constant.
If I am accelerating it doesn't happen, if it decelerates it doesn't happen.
 
Pinion angle? Checked today, seems like the angle of the DS is the same at the pinion.
Can take the car off the jackstands on the axle, put them on the body somewhere to get some angle on the DS at the pinion and try it again.
I'm making a list of all the suggestions to try on the weekend.
From what I know, the DS needs 1-2 degrees on it to keep it from binding.
 
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