Re: 76 C3 - Rear end whine..
06-23-2013, 10:46 PM
#1
Racer
Thread Starter
Re: 76 C3 - Rear end whine..
Just took the car out today for another shake down run.. The rear is whining and not sure where this will lead too.. Removed it from the car when I replaced the entire rear suspension and replaced the seals and rear gasket cover. Installed the new diff fluid adding the limited slip additive that the little red label at the plug called for along with the standard 90 weight oil..
The rear end is the factory stock unit and not sure what the gear ratio is. I figured it was good enough and reinstalled and worry about an upgrade later when funding would allow. The car was born a 350 automatic with air and now has a 4 speed w/o air and a motor pushing roughly 350 horse with old school cast iron chevy hump heads, edlebrock intake/carb, headers and chambered exhaust.
Is there anything I can do to rid the whine? It's very slight and can be heard at low speeds. When shifting into 2nd and 3rd gear the whine is present only slightly, but loud enough to be heard. My neighbor has two restored C3's and wasn't all that concerned with the noise when he heard it.
I guess I'll start looking around for a new gear set and was contemplating 3:70 or in the ball park. I like loads of grunt off the line and don't need to go 120 miles an hour, just something that would go fairly well at highway speeds. thoughts?
Mike
The rear end is the factory stock unit and not sure what the gear ratio is. I figured it was good enough and reinstalled and worry about an upgrade later when funding would allow. The car was born a 350 automatic with air and now has a 4 speed w/o air and a motor pushing roughly 350 horse with old school cast iron chevy hump heads, edlebrock intake/carb, headers and chambered exhaust.
Is there anything I can do to rid the whine? It's very slight and can be heard at low speeds. When shifting into 2nd and 3rd gear the whine is present only slightly, but loud enough to be heard. My neighbor has two restored C3's and wasn't all that concerned with the noise when he heard it.
I guess I'll start looking around for a new gear set and was contemplating 3:70 or in the ball park. I like loads of grunt off the line and don't need to go 120 miles an hour, just something that would go fairly well at highway speeds. thoughts?
Mike
06-25-2013, 09:37 PM
#5
Racer
I was just reading this post and decided to hijack (dont like to start brand new ones since there are tonnes of these)
I have a whine noise too! Its there for as long as I have the car (4 years). I go thru the gears, on hard launch 1,2,3 than I lift the foot of gas at, lets say 5k rpm in 3rd gear, there is a whine or hum as the revs drop down, the frequency changes as the speed and rpm decreases and it goes away at low RPM. at first I was thinking its the punpkin too but when I drop it to neutral the whine stops immediately:
1979 odo shows 70k
car had a lot of work done two owners ago
engine: small block all redone except short block,
3 speed auto with manual shift kit (fwd)
unknown rear end ratio- pretty short
stock rims with goodyear eagles 255's
again, sorry for highjack but I think it might be the same problem...
I have a whine noise too! Its there for as long as I have the car (4 years). I go thru the gears, on hard launch 1,2,3 than I lift the foot of gas at, lets say 5k rpm in 3rd gear, there is a whine or hum as the revs drop down, the frequency changes as the speed and rpm decreases and it goes away at low RPM. at first I was thinking its the punpkin too but when I drop it to neutral the whine stops immediately:
1979 odo shows 70k
car had a lot of work done two owners ago
engine: small block all redone except short block,
3 speed auto with manual shift kit (fwd)
unknown rear end ratio- pretty short
stock rims with goodyear eagles 255's
again, sorry for highjack but I think it might be the same problem...
06-27-2013, 07:31 PM
#7
see Post#2
There is no help. I am in the same boat. Mine is a fresh rebuild and was built incorrectly. It has a whine. The only solution is to rebuild. To make matters worse, the ring and pinion are usually permanently altered due to bad lash settings so a new ring and pinion is in order. Just take the pain and get it done right the first time. This time mine is going to Tracdog.
There is no help. I am in the same boat. Mine is a fresh rebuild and was built incorrectly. It has a whine. The only solution is to rebuild. To make matters worse, the ring and pinion are usually permanently altered due to bad lash settings so a new ring and pinion is in order. Just take the pain and get it done right the first time. This time mine is going to Tracdog.
06-27-2013, 08:27 PM
#8
Racer
Yeah, but I think it could be the tranny since it goes away when I throw it in neutral, plus the whine is only in 3rd gear when rpms are dropping down from high to low. So I would need to know if I need a pumpkin rebuild or a tranny rebuild ?
06-27-2013, 09:11 PM
#9
Hi PaPaPork,
The reason the noise ceases when you throw it in neutral is because you removed the load from the drive train. The diff or the trans will cease to make a gear alignment related noise when the load is relieved. A good test is to remove the three storage lids from the rear compartment and the inner lining of the two that don't contain the battery. Then take it for a drive and recreate the whine in your chosen gear. It will be pretty clear if your diff is the culprit.
Good luck.
The reason the noise ceases when you throw it in neutral is because you removed the load from the drive train. The diff or the trans will cease to make a gear alignment related noise when the load is relieved. A good test is to remove the three storage lids from the rear compartment and the inner lining of the two that don't contain the battery. Then take it for a drive and recreate the whine in your chosen gear. It will be pretty clear if your diff is the culprit.
Good luck.
06-27-2013, 11:18 PM
#10
Racer
thats good advice there, I was kind of hoping it might be the trans (because I would like the 200R4 swap). That might also explain why I had to fix the pinion seal
another question: since there is no chance I will repair this soon (haven t worked in over a year) is there any chance this will damage the core of the differential itself? I mean something like damage to the case when I would not be able to use it as a core?
another question: since there is no chance I will repair this soon (haven t worked in over a year) is there any chance this will damage the core of the differential itself? I mean something like damage to the case when I would not be able to use it as a core?
06-27-2013, 11:55 PM
#11
Melting Slicks
thats good advice there, I was kind of hoping it might be the trans (because I would like the 200R4 swap). That might also explain why I had to fix the pinion seal
another question: since there is no chance I will repair this soon (haven t worked in over a year) is there any chance this will damage the core of the differential itself? I mean something like damage to the case when I would not be able to use it as a core?
another question: since there is no chance I will repair this soon (haven t worked in over a year) is there any chance this will damage the core of the differential itself? I mean something like damage to the case when I would not be able to use it as a core?
06-28-2013, 03:58 AM
#12
Racer
That's great news! the sound doesn't bother me other than I keep worrying when I hear it...it almost sounds like some sort of turbine slowing down but only on 3rd gear from around 5000 to 2500 rpm. Well, I feel much better knowing I can leave it as is! thank you!
06-28-2013, 10:07 AM
#13
Melting Slicks
...when you drop it into neutral the sound goes away - that is still the rear differential. It's the transmission if the noise is coming from the transmission
- there are a billion blogs which talk about rear differential whine and what's wrong depending on when the whine happens so I won't retype the rules....
with that said, the only way to fix that whine is to replace the gears - which is a (at least) $500 repair
- there are a billion blogs which talk about rear differential whine and what's wrong depending on when the whine happens so I won't retype the rules....
with that said, the only way to fix that whine is to replace the gears - which is a (at least) $500 repair
06-28-2013, 11:50 AM
#15
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I have a whine in mine as well. Especially on curves. Figured it was the dif having posi (never had a car with it before) almost goes completely away when driving in a straight line. A few times i thought it was a jet taking off or landing as it sounded somewhat similar. Hope I am not wrong about it..
06-28-2013, 01:09 PM
#16
Racer
thanks for or the reps gents!
now other thing start to bother me, the same person that worked on the diff most likely was involved in changing heads, cam and everything else on the long block.
PS.
Just a side story that I don't want to open new thread for. last month I my "GEN" light came on, luckily I made it home, I open the hood and what I see is an alternator that completely opened up - the body came apart, the rotating assembly was grinding on the case...I guess I can expect just about anything from my car (our cars)!
now other thing start to bother me, the same person that worked on the diff most likely was involved in changing heads, cam and everything else on the long block.
PS.
Just a side story that I don't want to open new thread for. last month I my "GEN" light came on, luckily I made it home, I open the hood and what I see is an alternator that completely opened up - the body came apart, the rotating assembly was grinding on the case...I guess I can expect just about anything from my car (our cars)!
06-28-2013, 01:34 PM
#17
Drifting
The noise can be gears or bearings. Trans or diff. If it is the trans you need to check it in 4th gear. 4th gear is direct drive. Gears 1-3 put a side load on the trans mainshaft. 4th gear has no side loading. If you have the same noise in 4th then it is most likely the diff.
More often it is the front pinion bearing making the noise on decel. To be the gears making noise they would have to be very worn out or someone has been in there and set them up wrong.
Under decel the ring gear is trying to pull the pinion into the diff putting a heavy load on the front bearing. If this bearing fails it will allow the pinion to move backwards and the teeth will eat the carrier.
If the rear pinion bearing is bad it will make noise on acel or decel. It will be more noticable on decel due to less engine noise. Same with the left side carrier bearing. The right side bearing never wears unless it has been run low on lube or from metal shavings in the lube.
Most common gear noise on a rebuilt diff is caused by too little backlash or the pinion being set too deep. It is most noticable when cruising at highway speed and slightly applying the gas. This rarely gets better with time. On a stock non-rebuilt diff the ring gear will wear to a point that the pattern runs of the heel of the tooth. This will only get worse with time. This is most common with the factory 3.55 gears because of the low tooth count 9-32. This is only during acel.
It is very rare for gears to make noise on decel. Unless someone set them up wrong during a rebuild. The coast (decel) pattern on the ring gear wears much less than the drive pattern. People that like to downshift and use the engine for slowing down (me) or like to hear the exhaust noise (definitely me) will have increased coast pattern wear.
More often the noise from the gears is caused by excessive wear in the carrier side bearings allowing the carrier to shift and change the gear pattern.
If the diff has been run low on lube and/or overheated then it could be any or all above. A leaking pinion seal is one sign of a bad pinion bearing but not an absolute reason.
Mike
More often it is the front pinion bearing making the noise on decel. To be the gears making noise they would have to be very worn out or someone has been in there and set them up wrong.
Under decel the ring gear is trying to pull the pinion into the diff putting a heavy load on the front bearing. If this bearing fails it will allow the pinion to move backwards and the teeth will eat the carrier.
If the rear pinion bearing is bad it will make noise on acel or decel. It will be more noticable on decel due to less engine noise. Same with the left side carrier bearing. The right side bearing never wears unless it has been run low on lube or from metal shavings in the lube.
Most common gear noise on a rebuilt diff is caused by too little backlash or the pinion being set too deep. It is most noticable when cruising at highway speed and slightly applying the gas. This rarely gets better with time. On a stock non-rebuilt diff the ring gear will wear to a point that the pattern runs of the heel of the tooth. This will only get worse with time. This is most common with the factory 3.55 gears because of the low tooth count 9-32. This is only during acel.
It is very rare for gears to make noise on decel. Unless someone set them up wrong during a rebuild. The coast (decel) pattern on the ring gear wears much less than the drive pattern. People that like to downshift and use the engine for slowing down (me) or like to hear the exhaust noise (definitely me) will have increased coast pattern wear.
More often the noise from the gears is caused by excessive wear in the carrier side bearings allowing the carrier to shift and change the gear pattern.
If the diff has been run low on lube and/or overheated then it could be any or all above. A leaking pinion seal is one sign of a bad pinion bearing but not an absolute reason.
Mike
06-28-2013, 01:35 PM
#18
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St. Jude Donor '05
I live with mine, all new never whined when I had it put together
10 yrs later after being stored it whines some oh well. Changing gear lash/preload wont fix it. Turn up the radio
10 yrs later after being stored it whines some oh well. Changing gear lash/preload wont fix it. Turn up the radio
06-28-2013, 02:43 PM
#19
Melting Slicks
I have a whine in mine as well. Especially on curves. Figured it was the dif having posi (never had a car with it before) almost goes completely away when driving in a straight line. A few times i thought it was a jet taking off or landing as it sounded somewhat similar. Hope I am not wrong about it..
06-28-2013, 04:47 PM
#20
Racer
The noise can be gears or bearings. Trans or diff. If it is the trans you need to check it in 4th gear. 4th gear is direct drive. Gears 1-3 put a side load on the trans mainshaft. 4th gear has no side loading. If you have the same noise in 4th then it is most likely the diff.
More often it is the front pinion bearing making the noise on decel. To be the gears making noise they would have to be very worn out or someone has been in there and set them up wrong.
Under decel the ring gear is trying to pull the pinion into the diff putting a heavy load on the front bearing. If this bearing fails it will allow the pinion to move backwards and the teeth will eat the carrier.
If the rear pinion bearing is bad it will make noise on acel or decel. It will be more noticable on decel due to less engine noise. Same with the left side carrier bearing. The right side bearing never wears unless it has been run low on lube or from metal shavings in the lube.
Most common gear noise on a rebuilt diff is caused by too little backlash or the pinion being set too deep. It is most noticable when cruising at highway speed and slightly applying the gas. This rarely gets better with time. On a stock non-rebuilt diff the ring gear will wear to a point that the pattern runs of the heel of the tooth. This will only get worse with time. This is most common with the factory 3.55 gears because of the low tooth count 9-32. This is only during acel.
It is very rare for gears to make noise on decel. Unless someone set them up wrong during a rebuild. The coast (decel) pattern on the ring gear wears much less than the drive pattern. People that like to downshift and use the engine for slowing down (me) or like to hear the exhaust noise (definitely me) will have increased coast pattern wear.
More often the noise from the gears is caused by excessive wear in the carrier side bearings allowing the carrier to shift and change the gear pattern.
If the diff has been run low on lube and/or overheated then it could be any or all above. A leaking pinion seal is one sign of a bad pinion bearing but not an absolute reason.
Mike
More often it is the front pinion bearing making the noise on decel. To be the gears making noise they would have to be very worn out or someone has been in there and set them up wrong.
Under decel the ring gear is trying to pull the pinion into the diff putting a heavy load on the front bearing. If this bearing fails it will allow the pinion to move backwards and the teeth will eat the carrier.
If the rear pinion bearing is bad it will make noise on acel or decel. It will be more noticable on decel due to less engine noise. Same with the left side carrier bearing. The right side bearing never wears unless it has been run low on lube or from metal shavings in the lube.
Most common gear noise on a rebuilt diff is caused by too little backlash or the pinion being set too deep. It is most noticable when cruising at highway speed and slightly applying the gas. This rarely gets better with time. On a stock non-rebuilt diff the ring gear will wear to a point that the pattern runs of the heel of the tooth. This will only get worse with time. This is most common with the factory 3.55 gears because of the low tooth count 9-32. This is only during acel.
It is very rare for gears to make noise on decel. Unless someone set them up wrong during a rebuild. The coast (decel) pattern on the ring gear wears much less than the drive pattern. People that like to downshift and use the engine for slowing down (me) or like to hear the exhaust noise (definitely me) will have increased coast pattern wear.
More often the noise from the gears is caused by excessive wear in the carrier side bearings allowing the carrier to shift and change the gear pattern.
If the diff has been run low on lube and/or overheated then it could be any or all above. A leaking pinion seal is one sign of a bad pinion bearing but not an absolute reason.
Mike