Rear Noise

[vettn71]

When I took my 90 out this morning I noticed that at 50 mph or higher there seems to be a slight vibration and a low "rumble" type sound. Nothing very clear, more like an under tone to the tire noise. It doesn't change when the clutch is pushed in, and under 50 it doesn't seem to be evident. I checked the bearings by jacking the car up and moving the tire with my hands at 3 & 9 and then at 6 & 12, but didn't feel any movement. Tried moving the half shafts and driveshaft, but didn't feel any play there, either. Tires are almost new and haven't had any issues with them. Any ideas?

Jim

[Jagdpanzer]

Had a similar experience after putting on a new set of GY D3s couple of years back. Turned out to be the tire balancing. Had the everything road-force balanced on a Hunter GSP9700 machine http://www.gsp9700.com/ (http://www.gsp9700.com/)
at a local tire shop and that solved it.

[rhipsher]

I've had the same damn thing I start to hear it from 68mph to 80mph. It's definitely speed related. It almost sounds like the tire roar of a big knobby tire on a 4X4. I thought it might be the drive shaft being out of balance. All my ujoints are brand new Splicers so I knew it wasn't them. And I got a four point alignment and that didn't take care of it. So I've just learned to live with it.

[USAFPILOT]

I was always told that a noise like that from the back of the car would be the rear end. I wonder? :dontknow:

[rhipsher]

I was always told that a noise like that from the back of the car would be the rear end. I wonder? :dontknow:Yeah but which part of the rear end would make a noise like that. I've thought of everything. Rear gears maybe? Wheel bearings? Tire balance? drive shaft balance? I gave up along time ago trying to pinpoint that noise and the cause. I just can't afford to throw money at it by replacing everything that it could be. I'm waiting for somebody to chime in and say they had the same problem and found what the cause was. This is the first time I've ever seen a post addressing this. I thought I was the only one. It doesn't seem to affect the drive ability. It's just kind of annoying.

[tomtom72]

You are sure that the fluid level is okay in the rear & trans? You don't think that this is a bad case of exhaust resonance, or something loose in the exhaust system? Or maybe the spare tire carrier is loose, or the jack is loose? The tires are okay, you didn't loose a weight off of a wheel or have a flat spot or a belt go bad?

I hate to say this but if it's not the rear hub bearings, and you are sure that all the u-joints are good on the 1/2 shafts and the drive shaft joints also.....then it only leaves the stub axles, carrier side bearings and pinion bearings.

Other than that I'm stumped. Usually a low pitch rumble is either the u-joint needles in the first stages of failure, or the rear bearings going south, usually the axle bearings make noise like that.

I wonder if those teflon washers used in the rear hubs could make this symptom if they wear excessively?

[rhipsher]

You are sure that the fluid level is okay in the rear & trans? You don't think that this is a bad case of exhaust resonance, or something loose in the exhaust system? Or maybe the spare tire carrier is loose, or the jack is loose? The tires are okay, you didn't loose a weight off of a wheel or have a flat spot or a belt go bad?

I hate to say this but if it's not the rear hub bearings, and you are sure that all the u-joints are good on the 1/2 shafts and the drive shaft joints also.....then it only leaves the stub axles, carrier side bearings and pinion bearings.

Other than that I'm stumped. Usually a low pitch rumble is either the u-joint needles in the first stages of failure, or the rear bearings going south, usually the axle bearings make noise like that.

I wonder if those teflon washers used in the rear hubs could make this symptom if they wear excessively?

I removed the spare and jack for wieght reduction. All the ujoints are brand new. Trans fluid is full. Not sure about the rear diff fluid. My wheel bearings have a little play in them but I don't think they would make a roaring noise. When I'm at 80mph I can put the car in neutral and as it coast down to around 68mph the roar pitch start to go down and gets quieter kinda like a single engine air plane dive bombing. It's tire rotation speed related not rpm related.

[QB93Z]

I don't know if this applies to your situation, but on the first long trip I took in my 1994 ZR-1 with new tires, when I got on the highway I got an unusual noise that I became convinced was the differential. It went on for a while and I amost abandoned our trip to return home for repairs. Then we exited from one interstate to another with a different road surface and the noise went away immediately. Since then I have noticed the noise on new asphalt surfaces. I guess my tires just don't like the texture of that stuff.

Jim

[rhipsher]

I guess some tire tread could be louder than others. The only other Z I've ever driven was Brads 92 and I drove it for two hours back to Houston and I didn't hear any noise at all. That car was nice and tight other than the sound of the corsa there were no other unusual noises. This sound is exclusive to the rear end and no where else. I think there are probably a good chunk of us that have an issue with our cars that has puzzled us for years that we'd love to to get resolved and this is mine. You can only look prod and poke so long before you just throw up your hands and just give up on it. One day I'll just take it to Corey and say fix it. And he will find it and fix the cause of that noise thats been bothering me all of these years in no time. I just have to get it over to him.

[vettn71]

It's nice to know this isn't an isloated issue. The thing that bothers me most is that I've owned the car for a year and haven't noticed it before. Maybe my hearing perked up or something. I am running Sumitomos, but again, this seems to be a new noise. I thought about the differential, but there's no leaks or seepage. As far as the u-joints, they seem tight, but I haven't tried to watch and listen with the car up on jack stands. Maybe I can convince one of my sons to get under the car when it's runnign 60mph in fourth!

Jim

[tomtom72]

I agree with Jim! It happens so much with my D3's that it's just back ground noise and I don't think about it much any more.

I notice that my GS-D3's will make different pitch noises depending upon the road surface material. Cement is the surface that really makes them sing, kind of like a stuka in a dive! Even different types of asphalt will yield different pitched noises.

Rick, just for chits & giggles, I'd give a check to the fluid level in the gear. JMHO.

:cheers:
Tom

Jim, I'd check the gear fluid level anyway. My car sat a lot before I got it and well seepage isn't the word for it....the seals thought they had no work to do. They seeped badly thru the first two fluid changes and then stopped. Low fluid level & or worn out fluid could cause a rear to make a low pitched growling noise....kind of the same noise a manual trans makes when it's low on fluid.

[jonszr1]

rick , arent your rear tires just about worn out ??? i had this problem on my 90 and after i got new tires thing got smooth again .dont know for sure if that this is your prob. just something to consider

[rhipsher]

rick , arent your rear tires just about worn out ??? i had this problem on my 90 and after i got new tires thing got smooth again .dont know for sure if that this is your prob. just something to considerYeah bro but even when they were new this sound was there. And transitioning to different road surfaces makes no difference. I can always count on it letting me know its still there. I am suspicious of rear gears or at least something to do with that area. You would think a giant bumble bee is on your tail.