Rear end noise?
03-08-22, 06:39 PM
#1
Rear end noise?
So, after driving my renesis swapped fb around for a few hundred miles, I've noticed some noises that I'm not sure how to identify. I'm not even sure if they're bad noises or fairly normal. I never drove this car before doing a huge amount of work on it including replacing all the running gear underneath, so I have no idea what is and isn't normal.
1. I have a dull roaring noise that starts around 20 mph and doesn't really increase in volume or frequency as speed increases. My theories on this are:
1. I have a dull roaring noise that starts around 20 mph and doesn't really increase in volume or frequency as speed increases. My theories on this are:
A) I haven't yet replaced my drum brake master cylinder with a disc brake one (planning on doing this as soon as I get home in a few weeks). From what I have gathered, the drum brake master puts a sort of pretension on the rear brakes, which when switching to discs can cause the brakes to drag slightly. I suppose I could confirm this by lifting the car up in the rear and checking the rear pads for dragging
B) My rear end is bad/pinion tension is incorrect. I have no history on the GSL-SE Rear that is in my car other than that I bought it from a member of this forum years ago, and from what I remember they believed it was in good working order. I honestly can't remember though, so if I bought this from one of y'all and you remember, please let me know.
C) This is normal road noise and I'm being a pansy because I've been driving newer vehicles for a few years. It's been almost 5 years since I last daily drove an old Japanese car, so I can't remember what "normal" levels of noise in the cabin are.
2. A soft whining noise coming from the rear end:B) My rear end is bad/pinion tension is incorrect. I have no history on the GSL-SE Rear that is in my car other than that I bought it from a member of this forum years ago, and from what I remember they believed it was in good working order. I honestly can't remember though, so if I bought this from one of y'all and you remember, please let me know.
C) This is normal road noise and I'm being a pansy because I've been driving newer vehicles for a few years. It's been almost 5 years since I last daily drove an old Japanese car, so I can't remember what "normal" levels of noise in the cabin are.
A) I have driven in some other older vehicles with LSDs (Foxbody Mustangs, Porsches, etc.) throughout the years and I have heard a similar noise from some of those cars. I'm not sure whether or not that is normal though, or if those cars were just poorly maintained. I also haven't heard what a KNOWN "good condition" limited slip sounds like for this particular car, so it's hard to know if mine is ok. Are these LSDs typically "vocal", or are they normally quiet.
B) My LSD is bad. Either the clutches are shot or something else in there is unhappy.
3. A hell of an exhaust leak:B) My LSD is bad. Either the clutches are shot or something else in there is unhappy.
This one is a known issue, my exhaust is some shitty exhaust shop job I got done a year ago just to keep from irritating my neighbors while I got the motor up and running. Any recommendations on an exhaust setup are appreciated. My gut instinct would be to go with a racing beat setup, but I've heard that their quality has gone down quite a bit recently.
I don't like asking anyone to diagnose issues over the internet, I'm more just trying to get a sense of what a "normal" sounding FB road car sounds like as far as cabin noise is concerned. Any advice/help is appreciated.
03-09-22, 05:52 AM
#2
I would suspect axle shaft bearings to start. If you're going to be going through the rear brakes, take it one step further and pull the axles and replace the bearings and collars. At least pull the axles and check them that way you will know if the bearings feel ok. This is a good time to replace the rear axle seals as well.
If the pinion bearing were going, typically you would hear bearing noise under acceleration or load and that noise would diminish as you let off the gas. It would be prominent in the rear end.
I would inspect the u-joints for play and for binding. I've had a rear u-joint that made noise but did not cause a vibration. Its worth a look.
If the pinion bearing were going, typically you would hear bearing noise under acceleration or load and that noise would diminish as you let off the gas. It would be prominent in the rear end.
I would inspect the u-joints for play and for binding. I've had a rear u-joint that made noise but did not cause a vibration. Its worth a look.
03-09-22, 07:08 PM
#3
84SE-EGI helpy-helperton
First off, they're pretty loud. Very loud compared to modern cars. What you may be hearing is normal wind and road noise being transmitted through the floor and body of the car, but here's a quick list (*from most likely to least likely) to help you turn the volume down by a few degrees;
1) Door Seals - these wear out through use and UV light, often deteriorating the point of crumbled rubber. This will let the airflow through, and being riht next to your head, sounds pretty loud. The noise also builds up to about 50-60mph, and then stabilizes. Any headwind makes it worse. If your doors close easily with it all buttoned up, your seals,may need to be replaced.
2) Window Seals and channels - as above, the window edge seals which line the outside can fall apart or crack which lets rain (*rust) into the door, but also wind noise. The felt channels in which the glass runs can also get bent or fall apart, which lets air get around them, adding to noise.
3) Transmission Mounts - the rear of the transmission has a rubber isolated mount at the body where the tunnel sits, and the two donuts here can give out, resulting in misalignment of the transmission in the tunnel. This leads to driveline noise, as the transmission is transmitting vibration to the body. Additionally, a rubber isolation mount bolts to the transmission and the cross-brace, and when it fails, it can allow movement of the trans, too.
4) Shifter Rubber Seals - there are 3 rubber isolators which prevent intrusion of road noise into the cabin at the shifter. Most of these get destroyed over time by lazy shops who cut around them drop the trans, and they're not cheap to replace (*but definitely worth it). All 3 are there by design and damp out the reflected engine and exhaust noise which is bounced upward back into the car. If yours are damaged or missing, these 3 parts make a HUGE difference in interior noise control.
5) Driveshaft U-joints- If they're bad, you get a notchy, thump sound, usually out of the back, which increases with speed. When the front goes, you get vibration. A new Mazda OEM driveshaft gets you back up and running, but Mazdatrix sells replacement shafts with replaceable joints that only weighs 13.8lbs. Get it, and you can do your own U-joints going forward.
6) LSD Slip Additive - GM makes a specific LSD Slip modifier required for clutch-type LSDs. If you don't add it, the clutches wear out and make a lot of noise as they slip. It's a necessity for this type of LSD, and your pumpkin housing will have a sticker on the back near the fill hole specifying it's need. Check and be sure by drain and replace the 90w gear oil, along with the required amount of LSD Slip additive.
7) Body Holes (rust) - rust never sleeps, and the most likely areas where you get interior noise are the floor pans and the rear suspension mounts, inside the storage bins. If you have holes through the body, all kinds of noise will get in. Weld over plates, or otherwise fix the rust problem, and you may help with noise inside the car.
I spent several $hundred on Dynamat and stripped out most of the interior of my car to access everything where I could put it, including inside the door panels, the co plate floor pan area, the rear deck, inside both rear fenders, the spare tire well, and inside the bin area. Even going so far as to run up inside the B-pillar areas and up the inside of the firewall. It helped, but as soon as you roll a window down or open the sunroof, it's loud again. It added about 30lbs of weight, and took me about a week to install and put it all back together, but it was worth doing. The doors shut with a satisfying THUMP.
Upshot: the older you get, the worse your hearing becomes and the car starts to get quieter!
1) Door Seals - these wear out through use and UV light, often deteriorating the point of crumbled rubber. This will let the airflow through, and being riht next to your head, sounds pretty loud. The noise also builds up to about 50-60mph, and then stabilizes. Any headwind makes it worse. If your doors close easily with it all buttoned up, your seals,may need to be replaced.
2) Window Seals and channels - as above, the window edge seals which line the outside can fall apart or crack which lets rain (*rust) into the door, but also wind noise. The felt channels in which the glass runs can also get bent or fall apart, which lets air get around them, adding to noise.
3) Transmission Mounts - the rear of the transmission has a rubber isolated mount at the body where the tunnel sits, and the two donuts here can give out, resulting in misalignment of the transmission in the tunnel. This leads to driveline noise, as the transmission is transmitting vibration to the body. Additionally, a rubber isolation mount bolts to the transmission and the cross-brace, and when it fails, it can allow movement of the trans, too.
4) Shifter Rubber Seals - there are 3 rubber isolators which prevent intrusion of road noise into the cabin at the shifter. Most of these get destroyed over time by lazy shops who cut around them drop the trans, and they're not cheap to replace (*but definitely worth it). All 3 are there by design and damp out the reflected engine and exhaust noise which is bounced upward back into the car. If yours are damaged or missing, these 3 parts make a HUGE difference in interior noise control.
5) Driveshaft U-joints- If they're bad, you get a notchy, thump sound, usually out of the back, which increases with speed. When the front goes, you get vibration. A new Mazda OEM driveshaft gets you back up and running, but Mazdatrix sells replacement shafts with replaceable joints that only weighs 13.8lbs. Get it, and you can do your own U-joints going forward.
6) LSD Slip Additive - GM makes a specific LSD Slip modifier required for clutch-type LSDs. If you don't add it, the clutches wear out and make a lot of noise as they slip. It's a necessity for this type of LSD, and your pumpkin housing will have a sticker on the back near the fill hole specifying it's need. Check and be sure by drain and replace the 90w gear oil, along with the required amount of LSD Slip additive.
7) Body Holes (rust) - rust never sleeps, and the most likely areas where you get interior noise are the floor pans and the rear suspension mounts, inside the storage bins. If you have holes through the body, all kinds of noise will get in. Weld over plates, or otherwise fix the rust problem, and you may help with noise inside the car.
I spent several $hundred on Dynamat and stripped out most of the interior of my car to access everything where I could put it, including inside the door panels, the co plate floor pan area, the rear deck, inside both rear fenders, the spare tire well, and inside the bin area. Even going so far as to run up inside the B-pillar areas and up the inside of the firewall. It helped, but as soon as you roll a window down or open the sunroof, it's loud again. It added about 30lbs of weight, and took me about a week to install and put it all back together, but it was worth doing. The doors shut with a satisfying THUMP.
Upshot: the older you get, the worse your hearing becomes and the car starts to get quieter!
The following 4 users liked this post by LongDuck:
04-26-22, 12:32 AM
#6
79 Red
iTrader: (1)
Join Date: Jun 2005
Location: Ballwin, MO
Posts: 105
Likes: 0
Received 0 Likes
on
0 Posts
MAZDAVERX 713b -
I've been told I have a rear pinion bearing "going out" (symptons as you describe above) and the best thing to do is just live with it, since once you take it apart it could lead to a multitude of other unforeseen problems. How difficult is the rear pinion gear to replace? are parts available?
(PS - I have been 'living with it' for a number of years, but it sure is aggravating when rest of car is near mint).
I appreciate your knowledge
Ron
I've been told I have a rear pinion bearing "going out" (symptons as you describe above) and the best thing to do is just live with it, since once you take it apart it could lead to a multitude of other unforeseen problems. How difficult is the rear pinion gear to replace? are parts available?
(PS - I have been 'living with it' for a number of years, but it sure is aggravating when rest of car is near mint).
I appreciate your knowledge
Ron
04-27-22, 05:59 AM
#7
The pinion bearing replacement involves removing the rear differential and taking it completely apart. The plus side is that in doing so, you will replace the carrier bearings as well as the pinion bearing and the pinion seal. You will want to replace the axle seals that keep the gear oil from seeping out in between the backing plate and the axle housing. Replacing the bearings will require some special tools for the carrier bearing replacement and the knowledge of how to set the proper backlash. You could always remove the differential from the axle housing and take it to a shop to be rebuilt.
You'll also want to replace the axle shaft bearings if you suspect any degradation of the bearings. Another us is that if you tackle this project, all of the rear bearings will have been replaced and your rear end will be quiet and reliable once again.
You'll also want to replace the axle shaft bearings if you suspect any degradation of the bearings. Another us is that if you tackle this project, all of the rear bearings will have been replaced and your rear end will be quiet and reliable once again.
Thread
Thread Starter
Forum
Replies
Last Post
rybrx7
3rd Generation Specific (1993-2002)
5
12-22-03 09:16 PM