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10/6/06 12:22am - Original Message: 'rear end clunk'
74lastofthebigblocks
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camas, WA - USA

Vette(s):
1974 t-top 454 #'s matching engine,ugly light green color to be repainted original corvette orange at a later date

Joined: 9/21/2006
Posts: 6
Hi everyone!I'm new to the corvette world with my first,a 74 454 that appears to be original except for paint.My problem is that whenever you put the car in reverse ,there is a clunk sound coming from the rear end area.Any ideas?I know NOTHING about corvette rear end/suspension systems.Thanks!Also,when viewed from behind the car, the rear tires sit at an angle with the tops further inward than the bottoms.Could this be that the spring is worn out?Thanks again!
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10/6/06 9:16am - Reply: 'rear end clunk'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19458
Welcome to the Shark Tank, first off!!!

A "clunk" in the rear when putting in gear can be a few things. First would be the front differential mount bushing. It is a rubber/steel mount that holds the front of the diff. to the chassis.
When the rubber deteriorates, it allows the diff. to flip up/down, as you put it in gear, or even sometimes when you first take off, or slow down(on-off the gas quickly). They are replacable fairly easily.


Second, you could have u-joints in the driveshaft, or either/both of the half shafts worn/damaged, that could cause a clunk noise. (There is also a possibility of the half shaft flanges being loose on the stub shafts. This is not a common issue, and doubtfull that it is your noise...just info for you.)

Finally, you could have wear in the ring/pinion gears in the differential. This usually manifests itself as a growling, or whine noise while driving, but can also make a clunking noise, depending on what may actually be worn.

My bet is the front diff. mount.   

                                             

Pt.# 582122 "Front Carrier Mount Kit"Adams' Apple2006-10-06 07:55:32

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Joel Adams
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10/6/06 9:40am - Reply: 'rear end clunk'
rick d
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williamston, NC - USA

Vette(s):
1969 coupe, 350, m22 trans, ac, black on black,

Joined: 1/19/2006
Posts: 353
sounds like a universal joint to me,,does it make a noise that increases as you speed up,,do you hear a squeek squeek as the car starts to move?RD

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10/6/06 3:52pm - Reply: 'rear end clunk'
74lastofthebigblocks
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camas, WA - USA

Vette(s):
1974 t-top 454 #'s matching engine,ugly light green color to be repainted original corvette orange at a later date

Joined: 9/21/2006
Posts: 6
Thanks for replying guys!It sounds to me like it probably is that front diff mount.I'll try that first as that's probably something fairly easy and affordable(besides I like easy and affordable!Smile)
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10/6/06 4:11pm - Reply: 'rear end clunk'
Ron 78 Lifetime Member
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BINGHAMTON, NY - USA

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Joined: 7/19/2003
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If you like easy and affordable ,you shouldn't have bought a Vette,LOLbut we're glad you did .Now we can help you fix itThumbs%20Up

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10/28/06 11:34am - Reply: 'rear end clunk'
joelbbvette
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Lutz, FL - USA

Vette(s):
72 Big Block Coupe 2nd Owner 92 Convertible 2nd Owner Lots of previous and all Manuals! The fun starts when all 4 are sliding!!!

Joined: 9/21/2006
Posts: 4
Ok, everyone helped on the clunk and I agree with the front mount. 
 
As for the tires camber.  There are two eccentric bolts on the mount just below the diff.  If these are at about 2 (left) and 10 (right) and the spring is towards the flat side, it is shot.  If not, jack up the car and use jack stands, mark the eccentric washer/bolt with a sharpee (so you know where you started), loosen the nut and move bolts inward a small amount and retighten.  Drive car forward and backward to settle suspension.  I use a level with 2 sockets taped to it so that I'm only on the rim.  Check for level and redo until vertical.  This is the garage floor alignment.  Now if you run out of room to pull the tires in, you need a new spring (easy to change).  A short term fix is to use large washers between the nut at the bottom of the spring bolt and the spring to raise the rear of the car.  If you change the spring, change the outboard spring bolts!!!
 
I had one of these nuts fail from age on a 64 Vette and it was WAY TOO Exciting and that was in my front yard so it was slow.CensoredCry
 
Joel
 
The fun starts when all 4 are sliding! (long before it was called drifting)Thumbs%20Up
 
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11/1/06 3:31pm - Reply: 'rear end clunk'
74stingray454
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Willow Grove, PA - USA

Vette(s):
1974 Stingray Coupe LS4 454 Dark Brown Metallic with Deluxe Saddle interior

Joined: 10/27/2006
Posts: 232
MY 454 equipped car has the same sound, I just chalked it up to having so many u-joints and having the big block.... guess Ill take a closer look.
 
the poop of it is, during the summer, I had it at a corvette shop to have the rear suspention worked on and said to them to change what ever needs changed as I did not have my garage built yet.....
 
 
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11/2/06 6:15pm - Reply: 'rear end clunk'
PSU 98
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Shenandoah, PA - USA

Vette(s):
1982 Chevrolet Corvette

Joined: 10/18/2006
Posts: 328
I've got the same noise, a clunk when shifting the car into D or R.  It also has a noticeable squat when transferring gears from P.  Sounds like it just could be that front diff. mount, guess I have another new part to add to my wish list  Ouch

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11/2/06 9:25pm - Reply: 'rear end clunk'
74lastofthebigblocks
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camas, WA - USA

Vette(s):
1974 t-top 454 #'s matching engine,ugly light green color to be repainted original corvette orange at a later date

Joined: 9/21/2006
Posts: 6
Thanks joel for the reply.I'll try some of your suggestions when I get home as I am out on the road right now.Smile
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11/2/06 9:37pm - Reply: 'rear end clunk'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19458
[QUOTE=PSU 98] I've got the same noise, a clunk when shifting the car into D or R.  It also has a noticeable squat when transferring gears from P.  Sounds like it just could be that front diff. mount, guess I have another new part to add to my wish list  Ouch[/QUOTE]

Independant rear suspensions do the squat when put in Drive. This is normal. If you put it in reverse, it will raise up a bit. A clunk noise when putting into gear can be the mount, u-joint(s), bushing wear, etc. Just have to put it up, and check each area carefully.

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Joel Adams
C3VR Lifetime Member #56    
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             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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11/16/06 6:14pm - Reply: 'rear end clunk'
PSU 98
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Shenandoah, PA - USA

Vette(s):
1982 Chevrolet Corvette

Joined: 10/18/2006
Posts: 328
Was just wondering if it was possible to change that front mount without disconnecting the rear of the driveshaft... doesn't seem to be as much room in there as I thought Ermm PSU 982006-11-16 16:15:09

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11/16/06 7:57pm - Reply: 'rear end clunk'
OH6A Lifetime Member
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Cadiz, KY - USA

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64 Convertible 73 Coupe 74 Convertible 63 Corvair Spyder Convertible

Joined: 8/26/2002
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Rear tires in at the top.  Try this.  Jack up the rear of the car so the rear tires are off of the ground.  Once the tires are off of the ground, grab each rear tire at the bottom and pull out.  If there is more than about 1/4", the inner ends of your differential side yokes are worn.  Very difficult and not cheap to repair.  First you take the rear end out and so on.  On one thread above, the guy told you how to get the alignment close but if the side yokes are worn, you will not be able to adjust them far enough out to make the rear tires rest straight up and down.  Side yoke will not get better if they are bad and you will wear the inside of the rear tires out with regularity.  Good luck!  



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11/17/06 8:38am - Reply: 'rear end clunk'
art-corvette
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Joined: 8/16/2005
Posts: 229
reading this topic i was able to solve my rear end clunk too... already got a bit worried about the clunk since i had replaced almost everything..... during restoration.. solution was simply tighten the bolt on the front diff mount Thumbs%20Up
 
art-corvette
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11/20/06 10:59am - Reply: 'rear end clunk'
joelbbvette
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Lutz, FL - USA

Vette(s):
72 Big Block Coupe 2nd Owner 92 Convertible 2nd Owner Lots of previous and all Manuals! The fun starts when all 4 are sliding!!!

Joined: 9/21/2006
Posts: 4
Wheel Bearing play is around .001 - .008 and the yoke play on differential is supposed to be less than .030 (this is from memory so I could be off some).  If the yokes are worn, you have to pull the rear end and it gets expensive.  You might as well do all 6 u-joints, 2 yokes, and rebuild the diff.  If you need to remove the half shafts here is the approach I use:  Put rear of car in air on JACK STANDS!  Now disconnect the strut rods (they are going to probably need new bushings anyway), and you can move the wheels out enough to get the half shaft loose.
 
I just switched mine from 3:08 to 3:55 and it appears I lost 5 MPH for the same RPMs in 4th.  Car feels better though.  Good luck
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11/20/06 11:49am - Reply: 'rear end clunk'
gs77vet
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Joined: 3/19/2005
Posts: 385
I have the same "clunk" when I go into reverse, as the car moves and warms up the clunk is not as bad if I need to use reverse again. I suggest you have your car aligned, front and rear, before you spend a bunch of money, might help. Welcome to the "Vette" world these babies are fun and EXPENSIVE. I promise they are worth it. Gene

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5/8/11 7:00pm - Reply: 'rear end clunk'
ryn9212000
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Vette(s):
1981 Corvette L81

Joined: 4/23/2011
Posts: 24
I havnt had my 81 very long but i must say this is by far the best  C3 forum, any question i have i find already posted with answers, print's and directions. think i found a home at C-3 VR.....

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5/9/11 6:48am - Reply: 'rear end clunk'
rod7515 Lifetime Member
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Red Lion, PA - USA

Vette(s):
1974 White 350 Corvette, TH400 Automatic 1972 Tangerine /Go Mango Convertible 383 Stroker, 2004r Automatic

Joined: 10/27/2006
Posts: 1172
Welcome Robert, You will find this forum to be the best. There are many great members that will lend a hand to help you in any way possible. Enjoy the site and the car.
Rodney


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5/9/11 5:57pm - Reply: 'rear end clunk'
ryn9212000
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Vette(s):
1981 Corvette L81

Joined: 4/23/2011
Posts: 24
thank you Rodney, i have wanted this car since 1981 i was 15 and said some day i will have that car and i love it..... ryn92120002011-06-02 20:23:54

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5/9/11 6:33pm - Reply: 'rear end clunk'
dskopp
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Oak Creek, WI - USA

Vette(s):
1981 Great White Shark. Red Interior, 350/190hp. PS, PB (SS), A/C CC, T-Tops, Going to remain as Stock as possible. Served three years in Active Duty Army, then Retired Air Force after 34 years! Badger State Vetts Car Club. 175,000 Original miles!!

Joined: 5/21/2008
Posts: 1956
Welcome Robert!!  I can help with 81 questions if you want.  Joel is the "guru" for everybody!!
DanHug  And by the way, Joel was describing the "Corvette Dance"  Squat in drive and hop in reverse!!!!  "You put your left foot in, you take your left foot out...."Rolling On The Floor Laughing
dskopp2011-05-09 16:37:09

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5/9/11 7:51pm - Reply: 'rear end clunk'
ryn9212000
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Vette(s):
1981 Corvette L81

Joined: 4/23/2011
Posts: 24
nice 81 Dan, i have it's twin.
Bobby.

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