I've still got the "CLUNK"!

[C3RVETTE]

Well,I have replaced the rear wheel bearings,all 6 U-joints,put in a poly "snubber",replaced the differential fluid with synthetic w/posi additive.And I still have a clunking sound when making quick turns,and it still makes a loud clunk when it slams into reverse when the RPM's are too high(typically when cold).I guess my tranny is out of "adjustment",or the rear end is going bad?I have a '79 with a TH-350.ad

 

[Vettehead Mikey]

Have a look at the transmission mount

 

[GerryLP]

C3,


The front differential mount should be checked. Before the Cruise Fest, I checked mine and it was loose. I suspect that a broken one could cause the "clunk" sound also.

 

[C3RVETTE]

C3,


The front differential mount should be checked. Before the Cruise Fest, I checked mine and it was loose. I suspect that a broken one could cause the "clunk" sound also.

Isnt that the snubber I mentioned,or is it something else? And I havent checked the tranny mount yet.

 

[vmrod]

Besides the tranny mount, is it possible that the crossmember-differential-carrier-support bushing might be bad?

 

[Stallion]

When you say "clunk", what do you mean? Do you mean a loud bang that is just once? Or a rubbing sort of sound? How does the rear spring look?

 

[tomtom72]

Hi Jon, don't know if this will help, but sounds like there are two problems,separate from each other. 1.) turning( I gather switch back type l's & r's), 2.)Going in gear clunk. Hope I have it right? Problem #2: does it do it when going into drive? If Yes,then look for something external to the tranny, like the guys said trans mount,carrier stability,rear support stability,camber rod plate, spring mount. If the clunk is only in reverse engagement then sounds like internal problem( I can't offer anything, don't know much about AT's). Problem #2: Do you hear one loud clunk for each change in direction? Do you hear a series of clunks until you return to straight, and then the clunks start again when you turn the other way? I had a ' 72 so I am not sure the center sections are the same. If they are, the one clunk symptom could be weak pre-load springs and or a problem with the gears on the cross shafts( unlikely on the cross shaft & gears). The series of clunks when doing L's & R's indicate a posi clutch pack problem, which when it gets real bad it does it in a straight line. The clutchs could be burnt and or the pre-load cage with the springs could be bad( usually just the springs). Most of the time the posi fluid is N/G and it gets gummy and R&Ring it wont fix the problem you gotta flush out the carrier with CRC or tranny fluid then fresh refill and test it. Hope this adds something to the resolution. tomtom72

 

[C3RVETTE]

Hi Jon, don't know if this will help, but sounds like there are two problems,separate from each other. 1.) turning( I gather switch back type l's & r's), 2.)Going in gear clunk. Hope I have it right? Problem #2: does it do it when going into drive? If Yes,then look for something external to the tranny, like the guys said trans mount,carrier stability,rear support stability,camber rod plate, spring mount. If the clunk is only in reverse engagement then sounds like internal problem( I can't offer anything, don't know much about AT's). Problem #2: Do you hear one loud clunk for each change in direction? Do you hear a series of clunks until you return to straight, and then the clunks start again when you turn the other way? I had a ' 72 so I am not sure the center sections are the same. If they are, the one clunk symptom could be weak pre-load springs and or a problem with the gears on the cross shafts( unlikely on the cross shaft & gears). The series of clunks when doing L's & R's indicate a posi clutch pack problem, which when it gets real bad it does it in a straight line. The clutchs could be burnt and or the pre-load cage with the springs could be bad( usually just the springs). Most of the time the posi fluid is N/G and it gets gummy and R&Ring it wont fix the problem you gotta flush out the carrier with CRC or tranny fluid then fresh refill and test it. Hope this adds something to the resolution. tomtom72

Thanks for all the info,guys.I now have a list of possibilities to check.The clunk going into turns...like taking a left or right fairly quickly....isnt a super loud clunk,but noticeable.It sounds as if something heavy slides left or right until it hits & stops. The other,possibly tranny related,clunk is if I dont wait until the rpm's are at a low idle and put it into reverse,is like theres play in in it and it clunks when it engages,& it does it also,at a lesser degree,when going into drive also.But like was mentioned as a possibility,I will check the trans mount.When I recently changed the rear end fluid to synthetic,it wasnt flushed,just "vacuumed" out & replaced(I have no drain plug).I hope the tranny or rear isnt going bad as I've just been laid off,so no money to work with,& the weather is getting nice around here.Maybe if I resist the urge to get on it & take it easy,things will hold together awhile.

 

[SG4206]

The front diff. mount might be loose , Some of the kits have a bolt sleeve that won't let you over tighten ; but in essence leaves enough slack to clunk when hit with torque from trans gear engagement.

Just a thought , seeing how you just replaced it .

 

[JohnZ]

When you changed the diff lube, did you add at least one bottle of GM Posi additive? Without it, you'll get Posi "chatter", especially when starting from rest going around a corner.

Most of the "poly" diff support bushing kits have bushings that are a lot thinner than the OEM bushings, and don't have the correct spacer sleeve; the front end of the support ends up too high, which screws up the rear U-joint angle and places the U-joint VERY close to the underbody tunnel.

 

[curtis]

my vette had a serious clunk when backing up then applying the brakes. clunk sounded like from the center of the car. It was worn out rubber bushings inthe upper control arms on the left front. new bushings no more clunk. seems when the front wheel started to stop under braking in reverse the body of the car kept moving down the shaft to the end where it clunked to a stop. is it possible you are looking at the wrong end of the car?

 

[tomtom72]

Jon, after reading your last post I think I am at the wrong end of the car on the L & R turning thing! The man with the A-arm post has the place to look. I did not understand your first description correctly. The description you gave in your last post makes me wanna look in the front end also. tomtom72