73 rear end noise
Thread Starter
Racer
Joined: Oct 2006
Posts: 473
Likes: 6
From: New Port Richey FL
73 rear end noise
Hello all and thanks in advance for your help. My 73 convertible is making some noise in the rear. Right now it is most noticeable when I'm making a right turn and it sounds like the noise is at the right rear. Its rather loud and sounds sort of like a dragging brake. It continues for several yards after straightening out and then goes away. I have not noticed it on left turns. I took off my right rear rotor and verified that it is not parking brake related, as someone before me had removed the shoes and other parts I would have expected to find in there. With the rear jacked up I didn't notice any slack in the half shafts or u-joints. I did notice what I would call binding when I tried to rotate the right rear axle at two positions during the rotation. I'm guessing that that was from the angle of the half shafts but I suppose it could be something else. Any ideas ... er.. any well thought out ideas are appreciated. Thanks!
Heel & Toe
Joined: Sep 2006
Posts: 19
Likes: 0
From: Dallas Georgia
You said binding in 2 positions during rotation, was this with the brake caliper on or off? If it goes away with the caliper off, possible wrapped rotar. Next I'd take hold of the top and bottom of the wheel and check for bearing wear or slop. Not sure if this can be done with rear wheels or not but I know you can with the front. Interested in hearing what the problem is. Have the same year good luck.
Le Mans Master
Joined: Jul 2006
Posts: 8,117
Likes: 104
From: charlotte north carolina
while rebuilding the drive train, i noticed that with the wheels in full downward deflection (car supported on frame) the u joints rubbed and prevented full rotation of the wheels. i did some judicious grinding on the flanges to prevent contact. i didn't think it would be a problem in normal operation because the wheel wouldn't extend down fully, but i didn't want bubba to force the rotation and distort the bearings some time in the future.
Burning Brakes
Joined: Dec 2005
Posts: 1,179
Likes: 100
From: cranford nj
If the noise you hear is after you have driving for awhile,it's most likely your rear fluid.Drain the rear, go to your local GM dealer get the rear fluid and posi additive.Follow the directions (very easy and cheap $28.00) find a parking lot.Do figure 8's for about 10 min.Been there!
Melting Slicks
Joined: Mar 2006
Posts: 3,342
Likes: 7
From: Connecticut
Originally Posted by blue by you
If the noise you hear is after you have driving for awhile,it's most likely your rear fluid.Drain the rear, go to your local GM dealer get the rear fluid and posi additive.Follow the directions (very easy and cheap $28.00) find a parking lot.Do figure 8's for about 10 min.Been there!
This would be my first guess and least expensive fix
After a period of time the clutch lube seperates from the gear oil
The first time I heard this noise I thought I lost a tooth on the ring gear
Changed the oil, put in 4 ounces of GM limited slip additive, did the figure 8 thing and all was fine.
Racer
Joined: Aug 2006
Posts: 330
Likes: 3
From: Wellington, New Zealand
Sounds like a classic LSD clutch pack problem they slip and grab when they are low on lube or have had the wrong lube in them. Its a bit strange that its only one side grabbing, but I agree with the other threads change the oil and use the correct additive and with a little luck you will fix the problem.
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Thread Starter
Racer
Joined: Oct 2006
Posts: 473
Likes: 6
From: New Port Richey FL
Sorry guys, I've got a bag in the garage with diff oil and friction modifier, but other things have been pushed up on my honey-do list. Now that the spa is built, I can change the diff oil this week after work. Worse case I'll do it next week when I'm on vacation. Is it bonehead simple to change out the oil? I'm hoping for some kind of drain plug, I saw the fill plug while I was inspecting the rotor. Still has its red tag on it. Thanks again for all your help and patience.
Thread Starter
Racer
Joined: Oct 2006
Posts: 473
Likes: 6
From: New Port Richey FL
Hello all that may still be reading this old thread. I still haven't changed out my diff oil yet (maybe tomorrow) but my noise has gone away and has been replaced with a louder more annoying problem. I have a definite "clunk" on acceleration from a stop and when I go on or off the throttle. I'm thinking its the rubber bushing that holds the front of the diff up. I've inspected all the u-joints in the half shafts and they appear to be good. I've rocked the car while under it and couldn't find any slack there. Also tried just grabbing the half shaft and twisting it and again found nothing. I realize I've missed the drive shaft u-joints, but I'll take a look at them when I have the car jacked up. Any other ideas? Anyone changed out those bushings before? Thanks again!
Instructor
Joined: Oct 2005
Posts: 143
Likes: 0
From: Independence MO
Changing rear end oil
I had a bad noise in my '77 when I first got it and it and the rear end oil was low. I saw no leaks but it just did not have enough oil in it. I wanted to change the oil and did not see any drain plug and taking the back cover off was WAY too much work!! So I drilled a 1/4" hole in the bottom of the rear end and drained the oil and tapped it with a pipe tap and scewed in a plug. Added the right amount of oil and additive and no problems now. NOW I can change the rearend oil with no problems!!
Le Mans Master
Joined: Nov 2001
Posts: 8,829
Likes: 1,959
From: LONG ISLAND
2025 C3 ('68-'73) of the Year Finalist - Unmodified
2024 C3 of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified
Exact Same Noise !!!
Originally Posted by Green73
Hello all that may still be reading this old thread. I still haven't changed out my diff oil yet (maybe tomorrow) but my noise has gone away and has been replaced with a louder more annoying problem. I have a definite "clunk" on acceleration from a stop and when I go on or off the throttle. I'm thinking its the rubber bushing that holds the front of the diff up. I've inspected all the u-joints in the half shafts and they appear to be good. I've rocked the car while under it and couldn't find any slack there. Also tried just grabbing the half shaft and twisting it and again found nothing. I realize I've missed the drive shaft u-joints, but I'll take a look at them when I have the car jacked up. Any other ideas? Anyone changed out those bushings before? Thanks again!
mine started doing the same recently ! letting off the gas, big bang / clunk in rear, thought also of the carrier bushing, but how can you check that ? anyways i'm going to change my fluid as well, even if it doesnt correct thta other noise which i also have it couldnt hurt to change it anyways !!!
i'm going to watch what happens here.........ZIXXX PACKER
Burning Brakes
Joined: Dec 2005
Posts: 1,179
Likes: 100
From: cranford nj
If you don't have a drain plug, which most don't go get get your wifes turkey baster and suck out all the fluid.Then on your way back from doing figure 8's stop by the store and buy a new one for her.
Burning Brakes
Joined: Sep 2006
Posts: 851
Likes: 10
From: Palm City, FL
A clunk on accel or when letting up sounds more like a u-joint... or a trailing arm bushing. Check all 6 u-joints and the training arms. Could also be the bushing that holds the diff up. I had all of these when mine made clunking.
Noise while turning could be as discussed the diff fluid. If you are getting binding, then it's something else.
If you are getting multiple clunks that you can feel in the acceleration of a turn can be an LSD problem that new fluid might fix (It didn't in my camaro).
Noise while turning could be as discussed the diff fluid. If you are getting binding, then it's something else.
If you are getting multiple clunks that you can feel in the acceleration of a turn can be an LSD problem that new fluid might fix (It didn't in my camaro).
Team Owner
Joined: May 2005
Posts: 31,497
Likes: 1,313
From: Huntsville AL
Originally Posted by blue by you
If you don't have a drain plug, which most don't go get get your wifes turkey baster and suck out all the fluid.Then on your way back from doing figure 8's stop by the store and buy a new one for her.
Suck out as much of the rear gear oil as you can get out through the fill plug hole. Then fill with new posi lube and gear oil.
The fun part is the figure 8's in the parking lot.
Le Mans Master
Joined: Nov 2001
Posts: 8,829
Likes: 1,959
From: LONG ISLAND
2025 C3 ('68-'73) of the Year Finalist - Unmodified
2024 C3 of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified
How Much ??
How much limited slip lube goes in with the regular gear oil ?
i'm going to try it..........cant hurt, canalways help change of fluids, i have had the car over 5 years & have not changed it nor do i know how long it's been. What amount of time or miles should it be [B]changed ? curious ?
ZIXXX PACKER
i'm going to try it..........cant hurt, canalways help change of fluids, i have had the car over 5 years & have not changed it nor do i know how long it's been. What amount of time or miles should it be [B]changed ? curious ?
ZIXXX PACKER
Thread Starter
Racer
Joined: Oct 2006
Posts: 473
Likes: 6
From: New Port Richey FL
Still haven't changed out the fluid yet, but did get my car up on the lifts at my friends place. After on the regular lift and not finding anything crazy, we put it on the drive on lift. On there and moving the driveshaft back and forth we found play in the carrier bearings. All the U-joints looked fine. There was some movement in the front carrier mount bushing also. I'll be removing the diff and sending it to the local diff repair shop. Then begins the long (read expensive) process of basically rebuilding the hole rear end. Many of my bushings are original and definitly showing thier age. Judging sizable oil spot on the bottom of the right storage compartment, its something that needs to be address sooner or later. In this case, its going to be sooner. Just wish it would have popped up later... this is convertible weather in Florida. I shall keep everyone updated. Thanks!
Melting Slicks
Joined: Mar 2006
Posts: 3,342
Likes: 7
From: Connecticut
Originally Posted by 427SIXPACK
How much limited slip lube goes in with the regular gear oil ?
Put the additive in before you add the gear oil, then after you add the gear oil do the figure 8's in a open parking lot for a few minutes
Works wonders