clunking noise REAR END?
Tech Contributor
Joined: Aug 1999
Posts: 15,179
Likes: 3,999
From: Connecticut, USA
Grinding could be very worn side yokes hitting the housing. You might want to look at this asap if that is the case you'll wreck the diff if it is.
There should be a 1/8 boss at the yoke seal.
There should be a 1/8 boss at the yoke seal.
Burning Brakes
Joined: Oct 2007
Posts: 946
Likes: 0
From: Lake Geneva WI
Well, I am pretty sure I have two problems/issues... Anyway, I am pretty sure that the clunk is the cushion.. The grind? Who knows.. I'll re-lube the diff and see if that makes a diff (no pun).
Heel & Toe
Joined: Apr 2007
Posts: 22
Likes: 0
I just changed my gear oil after reading some earlier post and the noise has ceased. The clunking noise was occcuring in my '73 primarily when i turned from a direct line backing or going forward at slow speeds. A whining noise like a tire with low pressure could also be heard when driving forward at high speeds. All that ceased when the differential oil was changed. Used Royal Purple 75-140 Wgt gear oil. Worked great. Got it at an Oreillys auto parts store. Its well worth the $12 a quart price tag when facing a possible rear end rebuild price. Took me about 1 hr to change. pumped out the old oil (which was black) and install new...
Racer
Joined: Apr 2008
Posts: 408
Likes: 6
From: Santa Clarita CA
Definitely not comparing apples to apples here but that's what happened when a shop changed the fluid in my C5 within the first year after I bought it, and they didn't know about the friction additive that GM uses in the C5s (and I gather from reading this in the older Vettes as well). Needless to say I didn't know about it either at the time. It would clunk and sometimes grate as I recall, mostly while slowly cornering (or at least that's when I could hear it), like turning onto my street. You'd think that your rear dif is completely shot by the sound of it, but adding the friction additive will make it go away, usually with no harm if done reasonably soon.
Last edited by EDenney; May 12, 2008 at 04:01 PM.
Cruising
Joined: Jan 2007
Posts: 14
Likes: 0
I have the same noise as platzie described. Changed the strut rod busshings and the rear fluid and checked all the other bushings. The noise is still there, but is much, much quieter. It used to only take 1/4 throttle and it would bang like crazy while I accelerated. Now it takes full throttle and it is a pretty faint banging. I'd like to stop the sound completly, but I am running out of things to fix.
Safety Car
Joined: Aug 2006
Posts: 4,102
Likes: 1
From: Forsyth Illinois
I would check the trailing arm mounts,as mentioned earlier in the thread.My 68 has a bang on acceleration,and a bang,if I come done thru the gears real hard.Also,I dump the clutch to kill the car when parking it in the shop,and you will hear it.it's just the passenger side,and keep going thru tires over there.
It will be getting some attention soon...as soon as I can get some customer's cars gone.....
It will be getting some attention soon...as soon as I can get some customer's cars gone.....
Burning Brakes
Joined: Oct 2007
Posts: 946
Likes: 0
From: Lake Geneva WI
Outside of that I guess I am left with the fluid in the pumpkin, which I can tackle next, or something else.
As for the grinding noise... I've narrowed it down to the tranny mounts, possibly... I have to get a closer look, but it's not the engine mount. All my universals are new from the drive shaft to the half shafts, so I have no idea what else could cause that.. It's as if the tranny ****s position and the drive shaft is rubbing on the tunnel...
On the subject of replacing those cushions.. Anyone got a how to on that one. I can see the nut/bolt, which is all there is to it, but should I support the differential, replace the bolt? Anything else to look out for?
Thanks.
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Racer
Joined: Mar 2005
Posts: 286
Likes: 1
From: AZ
Similar situation
My lower differential cushion has sheared off!!!!
Left shaft is leaking at seal.
Right Rear wheel hangs about 2 inches lower while on jack stands.
I got serious problems.
Started with minor clunk, suspected a universal even though they are all new. Then the clunk went away for a week.
Now after a minor bump in the road, serious clunking and afterward a persistently noticeable minor clunk whenever it stops or starts.
How much damage can occur from having a loose Differential cushion?
Where else should I be looking for damage and is the rear wheel hanging lower involved in this?
(Or should I suspect something else for that?)
Any help is welcome.
Left shaft is leaking at seal.
Right Rear wheel hangs about 2 inches lower while on jack stands.
I got serious problems.
Started with minor clunk, suspected a universal even though they are all new. Then the clunk went away for a week.
Now after a minor bump in the road, serious clunking and afterward a persistently noticeable minor clunk whenever it stops or starts.
How much damage can occur from having a loose Differential cushion?
Where else should I be looking for damage and is the rear wheel hanging lower involved in this?
(Or should I suspect something else for that?)
Any help is welcome.
Burning Brakes
Joined: Oct 2007
Posts: 946
Likes: 0
From: Lake Geneva WI
Rear end clunk is officially gone.
QTY 3 90w gear oil
QTY 1 differential additive
I had the cushions replaced too, but I don't think they were to blame. Went with urethane, so they should last longer than I will have the gear.
Anyway, clunk is gone as far as I can tell.
QTY 3 90w gear oil
QTY 1 differential additive
I had the cushions replaced too, but I don't think they were to blame. Went with urethane, so they should last longer than I will have the gear.
Anyway, clunk is gone as far as I can tell.
Navigator
Joined: Jun 2008
Posts: 9
Likes: 0
Hi there 82xfire, i`ve had a vette72 for more than 25yrs, over that time the most problems i have had was banging rear end
. Some times i found it was all of the mentioned problems but most times i found that it was rear hub bearings gone, usualy spinning on the hub stub axle. this can cause a grinding sound, the bearings need to be a press fit and when they start to move around on the stub it will never be any better. i use alloy/wheels 285 tyres which don`t help, but since i did a rebuild and took `the bull by the horns` as it were, and put a lot of effort into the problem i have not had it return...yet, been 13 years and still going. This would also cause your wheel to look as though it was lower. U joints gone will cause this too.
. Some times i found it was all of the mentioned problems but most times i found that it was rear hub bearings gone, usualy spinning on the hub stub axle. this can cause a grinding sound, the bearings need to be a press fit and when they start to move around on the stub it will never be any better. i use alloy/wheels 285 tyres which don`t help, but since i did a rebuild and took `the bull by the horns` as it were, and put a lot of effort into the problem i have not had it return...yet, been 13 years and still going. This would also cause your wheel to look as though it was lower. U joints gone will cause this too.
Navigator
Joined: Jun 2008
Posts: 9
Likes: 0
Another way to rectify the banging from the limited slip diff, Is to do a rebuild of the diff unit and it basically amounts to using less preload of the friction plates...I here some of you saying `not the standard way`,`why don`t they do it to start off from new?`, this is not an idea of mine but from `Tom`s Diffs` those of you in the `know` will recognise his name. The reason is sound. the standard set-up causes the diff to lock up as a solid axle as per a go Kart (up to a certain torque) and you do not want this when turning a bend , but when setup as per `Tom`s Diffs` the friction plates are allowed to move freely as is needed when turning, BUT only if you do not put any power on, when you put the power on the plates tighten up and once again lockup as normal. So when you do your standing starts you will still be using you limited slip diff as normal.
I have had mine setup this way for the past 13 years and it was one of the most beneficial alterations i have done.
I have had mine setup this way for the past 13 years and it was one of the most beneficial alterations i have done.
Melting Slicks
Joined: May 2002
Posts: 2,781
Likes: 1,485
From: Savannah GA
Where can I buy the rear diff cushion mentioned? I'm pretty sure mine is shot. I get a bad clunking noise when shifting into reverse and into drive (auto trans). It will also clunk sometimes when making a tight left turn from a stop- like if im at a red light and turning left and then the light turns green and I go. I plan to replace the cushion and change out the fluid this weekend.
Burning Brakes
Joined: Oct 2007
Posts: 946
Likes: 0
From: Lake Geneva WI
Where can I buy the rear diff cushion mentioned? I'm pretty sure mine is shot. I get a bad clunking noise when shifting into reverse and into drive (auto trans). It will also clunk sometimes when making a tight left turn from a stop- like if im at a red light and turning left and then the light turns green and I go. I plan to replace the cushion and change out the fluid this weekend.
I got mine at the Jefferson Swapfest in Jefferson Wisconsin this spring... What a muddy mess... It was the last place we stopped at on the way out. I was standing in a tent in about 1 foot of mud and water freezing my underdressed, t-shirt wearing *** off.
Paid 10 bucks for the upper and lower together. They were from Corvette America, but the guys I bought the part from were from Beloit Wisconsin. I cannot find the card they gave me. I cannot for the life of me remember the name. It was damned cheap compared to the $40-50 that they retail for. These guys have just about everything for the C3 too, are close and inexpensive.
Maybe someone where knows who I am taking about? If not, I'll look around a bit harder for their card.
Melting Slicks
Joined: May 2002
Posts: 2,781
Likes: 1,485
From: Savannah GA
Ok, I found mid america has the upper (p/n 602-812) for $16.99 and the lower (p/n 602-810) for $14.99 Can someone confirm these are the correct parts? http://www.mamotorworks.com/corvette-4-303-1434.html It says on that page that the upper is a replacement style for 80-82. So does my 69 have an upper cushion or just the 80-82's?
Burning Brakes
Joined: Oct 2007
Posts: 946
Likes: 0
From: Lake Geneva WI
AFAIK it is. Those were the part numbers I had circled in my catalog and was going to order. Though I ended up getting them from that other place, and mine were urethane.
So you are looking at around $32 for the rubber. Again, I paid 10 bucks for the brand new urethane bushings.
Also, I'd recommend replacing the bolt as well, nuts, washer, etc.. You can find that at the local hardware store however.
So you are looking at around $32 for the rubber. Again, I paid 10 bucks for the brand new urethane bushings.
Also, I'd recommend replacing the bolt as well, nuts, washer, etc.. You can find that at the local hardware store however.
Burning Brakes
Joined: Oct 2007
Posts: 946
Likes: 0
From: Lake Geneva WI
I digress and leave this to the experts as I have no idea.