67 Chevelle - Clunk in Rear End - Chevelle Tech
Transmission & Driveline Transmissions and Differentials

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post #1 of 15 (permalink) Old Oct 6th, 19, 9:53 AM Thread Starter
 
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67 Chevelle - Clunk in Rear End

Hey Guys,

It's been so long since I have posted that I can't use my original username!

Anyway - my 67 SS went through a complete overhaul of all suspension parts back in 2006-2007, along with all new diff gears, bearings, Moser axles, axle bearings. If it moves, rotates, articulates, or reciprocates, it was freshened up. I've put about 6000 miles on the car since then. Over the past few months, I've been dealing with a clunk in the rear end/suspension that I can't seem to figure out.

I hear/feel it after these 2 scenarios:
1. I back out of the driveway, and just as I slip the clutch and start rolling forward and the weight shifts front to rear
2. If I pull 1st gear deeper than normal and then let off the gas, the weight shift from drive/coast and I hear the clunk

I have jacked it up and checked over everything - tightened all mounting points. My bushings (all of them) were new Moog pieces back in 2006. Body mounts at the same time. I have adjustable Edelbrock uppers - they are tight. Shock mounts are tight. Gas tank is tight. Wheels are tight. I have lowering springs in the rear that are strapped to the rear end houseing and I make sure they are seated properly to the frame each time I jack the car up.

I'm a stronger guy, but I can't yank on the wheels and get/feel any movement to indicate where this clunk is coming from.

I'm at a loss for direction at this point - any ideas on what else I can check? I don't want to go on a wild goose chase changing all of the suspension bushings again without properly diagnosing the problem.

Thanks in advance for any help you can provide

Jay
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post #2 of 15 (permalink) Old Oct 6th, 19, 9:57 AM
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Re: 67 Chevelle - Clunk in Rear End

Have you checked the driveshaft U-joints for play?
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post #3 of 15 (permalink) Old Oct 6th, 19, 11:52 AM Thread Starter
 
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Re: 67 Chevelle - Clunk in Rear End

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Originally Posted by blackhawkMC View Post
Have you checked the driveshaft U-joints for play?
I can't say I have directly. When I was under there this morning, the car was in gear. I gave the driveshaft a twist and nothing stuck out.
What is the best way to test/check the U joints?
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post #4 of 15 (permalink) Old Oct 6th, 19, 12:44 PM
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Re: 67 Chevelle - Clunk in Rear End

Suggest jack it up, hold the drive shaft and turn or have someone else try turning each wheel and see if you have excessive motion or back lash.

Or drain the axle and pull the cover. For some reason this type of problem typically does not heal itself.

I assembled a 410 axle with all new stuff years back. Backlash was in spec. It just seemed too much, so a couple years ago I pulled it apart and swapped some shims side to side and its been better since.

Look of for slack and metal parts in the bottom of the case.

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post #5 of 15 (permalink) Old Oct 6th, 19, 3:17 PM
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Re: 67 Chevelle - Clunk in Rear End

I had a clunk on my 66 that was hard to track down. It turned out that a bushing in one of the stock style rear control arms had popped out on one end.
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post #6 of 15 (permalink) Old Oct 6th, 19, 5:30 PM
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Re: 67 Chevelle - Clunk in Rear End

I was going to suggest the driveshaft U-joints, been there before...

I actually had a similar clunk, and it turned out to be loose/missing transmission cross-member to frame bolts... Whoops! Drivers side was fine, but passenger side were missing (and I had installed then previously). Just allowed the engine/trans to torque over, and lift the cross-member off the frame slightly, with a clunk when letting off...

Pretty noticeable during an auto-cross session...

And then during a break at the Auto-X, one of the course workers handed me a bolt and asked if it was mine... It was a Porsche event, and my car was one of only 2 old American cars, and it was an SAE Grade 8 bolt, not metric...

Once you go RAT, you never go back...
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post #7 of 15 (permalink) Old Oct 6th, 19, 7:20 PM
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Chris
 
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Re: 67 Chevelle - Clunk in Rear End

I have a clunk as well. Brand new Moser 12 bolt, brand new Denny's driveshaft. Manual trans as well.

What limited slip do you have? I have a Detroit Truetrack and there is a ton of play in the helical gears.

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post #8 of 15 (permalink) Old Oct 6th, 19, 10:14 PM
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Re: 67 Chevelle - Clunk in Rear End

While you are checking suspension bolts, check the front.

Inner nuts and bolts, upper and lower.
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post #9 of 15 (permalink) Old Oct 7th, 19, 8:18 PM Thread Starter
 
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Re: 67 Chevelle - Clunk in Rear End

Thanks for all of the help and suggestions. I have been checking bolts front and rear for a few months. It feels like a bushing/weight transfer issue and not a driveline lash sort of thing. So much so that when it first started happening, I thought it was a front right lower ball joint. Since then, I've been able to isolate it to what I believe to be the right rear.

Trans cross member bolts in place and tight

I pulled the rear UCA off the housing - bushing are in place and tight

I did a rear diff fluid change back in the spring of this year - didn't notice any issues or metal on the magnets. I was having the issue in advance of that fluid change

I'm at a loss for sure.

I need to check the U-joints still. I just feel like this clunk is suspension and not a "click" like you'd expect from bad U joints.
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post #10 of 15 (permalink) Old Oct 8th, 19, 3:28 PM
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Re: 67 Chevelle - Clunk in Rear End

long shot ... when you pull the driveshaft , smear some grease on splines and slip yoke -both in and out.Sticky splines can cause a clunk on takeoff
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post #11 of 15 (permalink) Old Oct 8th, 19, 9:32 PM
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Re: 67 Chevelle - Clunk in Rear End

Quote:
Originally Posted by driveshaft-texas View Post
long shot ... when you pull the driveshaft , smear some grease on splines and slip yoke -both in and out.Sticky splines can cause a clunk on takeoff
I've also heard that takes up some of the "slop".

OP, what limited slip do you have?

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post #12 of 15 (permalink) Old Oct 8th, 19, 10:21 PM
 
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Re: 67 Chevelle - Clunk in Rear End

From numerous experiences, I can say with certainty that driveshaft U-joints can cause a whole range of sounds - from clunking to screeching to dull whumps. One second theyíre loud, the next you canít tell anything is wrong.

Pull the shaft, check the universals, especially the rear.
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post #13 of 15 (permalink) Old Oct 8th, 19, 10:42 PM
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Re: 67 Chevelle - Clunk in Rear End

Quote:
Originally Posted by Bronze68 View Post
From numerous experiences, I can say with certainty that driveshaft U-joints can cause a whole range of sounds - from clunking to screeching to dull whumps. One second theyíre loud, the next you canít tell anything is wrong.

Pull the shaft, check the universals, especially the rear.
What do you check for?

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post #14 of 15 (permalink) Old Oct 9th, 19, 12:25 PM
 
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Re: 67 Chevelle - Clunk in Rear End

They always look unsuspecting on the outside. Every time I ended up pulling U-joint because I didn't know what else to look at, and sure enough, when I would remove the caps, the needle bearings were missing, turned to dust, etc. So, unfortunately, you'll have to go that far to be sure. Regardless, it's not a long job nor an expensive one if it turns out not to be the problem.

I obviously don't know how old yours are. Personally, I've never had a problem with the front, just always the back.


On another note, I too experienced a clunk in the rear before that wasn't a U-joint. It only occurred 1 out of every 10 times when pulling out. Turned out that the differential was literally coming apart. Ultimately, the prior owner had pretended to know how to drive a 5-speed. I ended up putting in a new clutch as well. This was in a 1995 Yukon GT.

Regardless, I would definitely start with the U-joints. They can cause a whole host of noises, on and off.
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post #15 of 15 (permalink) Old Oct 9th, 19, 12:32 PM
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Re: Help with new crate engine overheating

Quote:
Originally Posted by -SS454- View Post
What do you check for?
Condition of the needle bearings. I have to pull my Denny's shaft once in a while to check. Pull the shaft, and then pull each cap and inspect.

Denny told me to go 1350, and I didnt want to for such a stock ride. The man knows the shaft!

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