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!

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
C3VR Lifetime Member #56    
My Link


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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

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

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!)

If you like easy and affordable ,you shouldn't have bought a Vette,but we're glad you did .Now we can help you fix it

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C3VR Lifetime Member #93

Ok, everyone helped on the clunk and I agree with the front mount. 

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.

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 

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.

[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  [/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    
My Link


(click for Texas-sized view!)             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

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 PSU 982006-11-16 16:15:09

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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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

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 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.....

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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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

Welcome Robert!!  I can help with 81 questions if you want.  Joel is the "guru" for everybody!! dskopp2011-05-09 16:37:09

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nice 81 Dan, i have it's twin. Bobby.