Noise from rear end
05-26-2010, 08:05 PM
#1
Racer
Thread Starter
Noise from rear end
While making low speed turns I hear a knocking or banging sound from the rear of my 63 coupe.
It sounds like something loose in the rear compartment rolling and banging into the sides with turning. So much so that I looked and looked for a loose tool or can in the back or in the rear storage compartments. Came to realize it is coming from under the car, possibly from the differential or half shafts or somewhere close.
Possible causes?
It sounds like something loose in the rear compartment rolling and banging into the sides with turning. So much so that I looked and looked for a loose tool or can in the back or in the rear storage compartments. Came to realize it is coming from under the car, possibly from the differential or half shafts or somewhere close.
Possible causes?
05-26-2010, 08:16 PM
#2
Could be the positraction unit grabbing. Also wheel bearings, u-joints or worn suspension. Also check the bolts on the differential.
Time to put it on a rack and check it out.
Time to put it on a rack and check it out.
05-26-2010, 08:53 PM
#3
Drifting
Has your vehicle been sitting for some time?
If Yes, then it's probably your posi clutch plates. Just throw in a bottle of GM rear additive. It very well might fix your noisy rear end.
RK
If Yes, then it's probably your posi clutch plates. Just throw in a bottle of GM rear additive. It very well might fix your noisy rear end.
RK
05-26-2010, 10:58 PM
#4
Racer
Thread Starter
I'll try the additive.
05-26-2010, 11:04 PM
#5
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We used to take the burs off posi plates by going to an empty parking lot and doing figure 8's as tight as you can. 2 or 3 figure 8's and noise will be gone.
05-27-2010, 08:07 AM
#6
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Sounds like a 1/2 shaft U-Joint to me but like others said it wouldn't hurt to start by changing the rear end gear oil and re-filling with the GM posi lube. Do your figure 8's and see it that helps. When I bought my 68 a few years ago it was doing the same thing. I dumped the rear end gear oil, re-filled with 80/90 weight gear oil and one 4 oz bottle of GM posi lube. Did my figure 8's and the noise was gone.
05-27-2010, 08:18 AM
#7
Melting Slicks
Not if it is low on fluid or regular 85/90 weight was added with no posi additive. Not sure what would happen but I don't think it would be good.
05-27-2010, 10:12 AM
#8
Le Mans Master
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Jack the car up just a little so it tilts away from the fill hole on the rear differential. Remove the plug and stick your finger in the hole and try to feel some fluid. If none, I would definitely suck out any old fluid and add new gear oil at at least one or two pints of posi fluid. Also a good idea to check what you removed for any foreign matter like metal flakes and color of the old fluid before adding new just in case it's time for a rebuild. 
05-27-2010, 09:58 PM
#9
Racer
Thread Starter
OK I put 'er on jack stands this evening and crawled under. Ujoints all seem good and suspension pieces seem fine.
The noise seemed to be coming from under the drive tunnel just as it flared for the differential housing. I looked all around the front part of the differential and was taken by the very limited clearance between it and the body. Barely can get my fingers above the front yoke. While I was checking it out, I find a small block of wood wedged in between the diff and the body right there. I don't know if someone stuck it in there for some type of shim or what.
I did notice that the ujoints looked like they had been replaced, and the rubber "bumper" in front of the diff also looked new.
Finally, I was surprised that the parking brake cable was routed between the yoke of the diff and the bracket (above the bracket). Looking at the ASM, though, this seems correct.
So I guess I'll knock out the wood block, but I'm afraid to find out the hard way why someone put it there before! Could have bee done as part of assembling the snubber replacement or Ujoints.
Any thoughts on this?
What should the clearance be between the front yoke of the diff carrier and the body?
The noise seemed to be coming from under the drive tunnel just as it flared for the differential housing. I looked all around the front part of the differential and was taken by the very limited clearance between it and the body. Barely can get my fingers above the front yoke. While I was checking it out, I find a small block of wood wedged in between the diff and the body right there. I don't know if someone stuck it in there for some type of shim or what.
I did notice that the ujoints looked like they had been replaced, and the rubber "bumper" in front of the diff also looked new.
Finally, I was surprised that the parking brake cable was routed between the yoke of the diff and the bracket (above the bracket). Looking at the ASM, though, this seems correct.
So I guess I'll knock out the wood block, but I'm afraid to find out the hard way why someone put it there before! Could have bee done as part of assembling the snubber replacement or Ujoints.
Any thoughts on this?
What should the clearance be between the front yoke of the diff carrier and the body?
05-28-2010, 12:49 PM
#10
Safety Car
Sounds like a 1/2 shaft U-Joint to me but like others said it wouldn't hurt to start by changing the rear end gear oil and re-filling with the GM posi lube. Do your figure 8's and see it that helps. When I bought my 68 a few years ago it was doing the same thing. I dumped the rear end gear oil, re-filled with 80/90 weight gear oil and one 4 oz bottle of GM posi lube. Did my figure 8's and the noise was gone.
You must change the diff oil first.......AFTER you remove the wooden block. After you get clean new oil installed, WITH THE GM ADDITIVE ADDED, then drive the car and all should be good to go.
Chevrolet originally installed positraction diff fluid that had 'whale oil' in it. For EPA reasons, they no longer make that kind of Differential oil. Chevron has a very good 80-90 positraction fluid, but I always added the GM Additive supplement to be sure.
It is a dirty job both removing the old fluid and installing new. A hoist is best, and you will need a suction gun to pull out the old, and preferably a gear oil dispenser with pump, to replace the fluid. Install the additive first, then the new gear oil until it starts to run out the hole. Cap it up, and go drive and have fun.
If noise persists, the differential will have to be removed for rebuild. And then you have axel bearings.......trailing arm bushings......strut bushings..... and the list goes on. Suspension and differential item are always the 'last' to be restored.
Last edited by jimgessner; 05-28-2010 at 12:52 PM.
05-28-2010, 06:39 PM
#11
Drifting
So I guess I'll knock out the wood block, but I'm afraid to find out the hard way why someone put it there before! Could have bee done as part of assembling the snubber replacement or Ujoints.
Any thoughts on this?
What should the clearance be between the front yoke of the diff carrier and the body?
Any thoughts on this?
What should the clearance be between the front yoke of the diff carrier and the body?
You don't want to be cruising down the road, and have it fall out, only to find out the real hard way, that it's holding or spacing something of importance.
Do take some pics and post though before you remove....
Just my opinion,
RK
05-28-2010, 07:02 PM
#12
Le Mans Master
OK I put 'er on jack stands this evening and crawled under. Ujoints all seem good and suspension pieces seem fine.
The noise seemed to be coming from under the drive tunnel just as it flared for the differential housing. I looked all around the front part of the differential and was taken by the very limited clearance between it and the body. Barely can get my fingers above the front yoke. While I was checking it out, I find a small block of wood wedged in between the diff and the body right there. I don't know if someone stuck it in there for some type of shim or what.
I did notice that the ujoints looked like they had been replaced, and the rubber "bumper" in front of the diff also looked new.
Finally, I was surprised that the parking brake cable was routed between the yoke of the diff and the bracket (above the bracket). Looking at the ASM, though, this seems correct.
So I guess I'll knock out the wood block, but I'm afraid to find out the hard way why someone put it there before! Could have bee done as part of assembling the snubber replacement or Ujoints.
Any thoughts on this?
What should the clearance be between the front yoke of the diff carrier and the body?
The noise seemed to be coming from under the drive tunnel just as it flared for the differential housing. I looked all around the front part of the differential and was taken by the very limited clearance between it and the body. Barely can get my fingers above the front yoke. While I was checking it out, I find a small block of wood wedged in between the diff and the body right there. I don't know if someone stuck it in there for some type of shim or what.
I did notice that the ujoints looked like they had been replaced, and the rubber "bumper" in front of the diff also looked new.
Finally, I was surprised that the parking brake cable was routed between the yoke of the diff and the bracket (above the bracket). Looking at the ASM, though, this seems correct.
So I guess I'll knock out the wood block, but I'm afraid to find out the hard way why someone put it there before! Could have bee done as part of assembling the snubber replacement or Ujoints.
Any thoughts on this?
What should the clearance be between the front yoke of the diff carrier and the body?
Sounds like the body is sagging and the U-joint hits the fiberglass on those turns. Someone recognized this and was using the wood as a spacer to avoid/reduce this. Look for a thin line in the 'glass in that area as a point of contact.
My '64 did this except that it hit/rubbed during hard launches. This was after I had replaced the rubber bushings for aluminum.
My solution was to undo the front bolt that holds the rear end and use a big screw driver and pry the it away from its mount and add two fender washers in there. I never had a problem since.
05-28-2010, 08:27 PM
#13
Race Director
Sounds like the body is sagging and the U-joint hits the fiberglass on those turns. Someone recognized this and was using the wood as a spacer to avoid/reduce this. Look for a thin line in the 'glass in that area as a point of contact.
My '64 did this except that it hit/rubbed during hard launches. This was after I had replaced the rubber bushings for aluminum.
My solution was to undo the front bolt that holds the rear end and use a big screw driver and pry the it away from its mount and add two fender washers in there. I never had a problem since.
My '64 did this except that it hit/rubbed during hard launches. This was after I had replaced the rubber bushings for aluminum.
My solution was to undo the front bolt that holds the rear end and use a big screw driver and pry the it away from its mount and add two fender washers in there. I never had a problem since.
somewhat. I would replace the front bushing with original GM pieces. If that does not increase the clearance then probably the floor pan is sagging because the bulkhead behind the seats is loose or cracked - a very common problem. There is a fairly inexpensive fix for this - put some boards under the floor and jack it up carefully and place some rubber mounts between the body and the crossmember behind the seats. The company that sells the 5-speed change over kits makes a special bushing for this purpose (Kiesler I think). But, you may have a combination of problems going on here and probably need to change out the rear gear oil and install the GM posi additive as noted above.
Dan
05-31-2010, 08:38 PM
#14
Racer
Thread Starter
Sounds like the body is sagging and the U-joint hits the fiberglass on those turns. Someone recognized this and was using the wood as a spacer to avoid/reduce this. Look for a thin line in the 'glass in that area as a point of contact.
My '64 did this except that it hit/rubbed during hard launches. This was after I had replaced the rubber bushings for aluminum.
My solution was to undo the front bolt that holds the rear end and use a big screw driver and pry the it away from its mount and add two fender washers in there. I never had a problem since.
My '64 did this except that it hit/rubbed during hard launches. This was after I had replaced the rubber bushings for aluminum.
My solution was to undo the front bolt that holds the rear end and use a big screw driver and pry the it away from its mount and add two fender washers in there. I never had a problem since.
so changing the angle between the drive shaft and the differential (bay adding the washers on the front mount) did not cause any problems?
05-31-2010, 08:39 PM
#15
Racer
Thread Starter
somewhat. I would replace the front bushing with original GM pieces. If that does not increase the clearance then probably the floor pan is sagging because the bulkhead behind the seats is loose or cracked - a very common problem. There is a fairly inexpensive fix for this - put some boards under the floor and jack it up carefully and place some rubber mounts between the body and the crossmember behind the seats. The company that sells the 5-speed change over kits makes a special bushing for this purpose (Kiesler I think). But, you may have a combination of problems going on here and probably need to change out the rear gear oil and install the GM posi additive as noted above.
Dan
Can you describe the "bulkhead" further. Is it fiberglass or a part of the frame?
05-31-2010, 09:16 PM
#16
Le Mans Master
06-01-2010, 12:24 AM
#17
Race Director
Sounds like a 1/2 shaft U-Joint to me but like others said it wouldn't hurt to start by changing the rear end gear oil and re-filling with the GM posi lube. Do your figure 8's and see it that helps. When I bought my 68 a few years ago it was doing the same thing. I dumped the rear end gear oil, re-filled with 80/90 weight gear oil and one 4 oz bottle of GM posi lube. Did my figure 8's and the noise was gone.
OK I put 'er on jack stands this evening and crawled under. Ujoints all seem good and suspension pieces seem fine.
The noise seemed to be coming from under the drive tunnel just as it flared for the differential housing. I looked all around the front part of the differential and was taken by the very limited clearance between it and the body. Barely can get my fingers above the front yoke. While I was checking it out, I find a small block of wood wedged in between the diff and the body right there. I don't know if someone stuck it in there for some type of shim or what.
I did notice that the ujoints looked like they had been replaced, and the rubber "bumper" in front of the diff also looked new.
Finally, I was surprised that the parking brake cable was routed between the yoke of the diff and the bracket (above the bracket). Looking at the ASM, though, this seems correct.
So I guess I'll knock out the wood block, but I'm afraid to find out the hard way why someone put it there before! Could have bee done as part of assembling the snubber replacement or Ujoints.
Any thoughts on this?
What should the clearance be between the front yoke of the diff carrier and the body?
The noise seemed to be coming from under the drive tunnel just as it flared for the differential housing. I looked all around the front part of the differential and was taken by the very limited clearance between it and the body. Barely can get my fingers above the front yoke. While I was checking it out, I find a small block of wood wedged in between the diff and the body right there. I don't know if someone stuck it in there for some type of shim or what.
I did notice that the ujoints looked like they had been replaced, and the rubber "bumper" in front of the diff also looked new.
Finally, I was surprised that the parking brake cable was routed between the yoke of the diff and the bracket (above the bracket). Looking at the ASM, though, this seems correct.
So I guess I'll knock out the wood block, but I'm afraid to find out the hard way why someone put it there before! Could have bee done as part of assembling the snubber replacement or Ujoints.
Any thoughts on this?
What should the clearance be between the front yoke of the diff carrier and the body?
I have been there and done that. As a matter of fact, I need to find a parking lot and drive the shoot out of mine now.
06-01-2010, 11:04 AM
#18
Team Owner
Member Since: Oct 2000
Location: Washington Michigan
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06-01-2010, 02:04 PM
#19
Racer
Thread Starter
this could be the problem that the wood block was placed for
may or may not be related to the noise
what is the fix for the problem, from the pic it looks like removal of seats and carpet would give excellent access, then reinforce and rivet in new (or re-rivet old) steel?
Anyone done?
06-01-2010, 02:39 PM
#20
Racer
Thread Starter
fix?
this could be the problem that the wood block was placed for
may or may not be related to the noise
what is the fix for the problem, from the pic it looks like removal of seats and carpet would give excellent access, then reinforce and rivet in new (or re-rivet old) steel?
Anyone done?