rear whirling noise driving me crazy

[madkaw]

I know there a ton of threads like this, because I have read a bunch trying to get some ideas. Here's the facts

 

9/71 chassis-L-24, bwt-5, 89 LSD

Shortened and balanced main shaft, half shafts newer universals and also balanced

Tires new, wheels new, brakes new(wildwoods), rear bearings new.Pinion angle 2 degrees and parallel

 

Symptoms;

whirling out of balance sound from 45/50--70mph coming from rear

Changing gears at a constant speed affects the volume of the noise

At 60mph 3rd gear noise is hard to hear-almost non existent,4th gear it is the loudest, 5th gear reduces noise , but is still apparent

Disengaging clutch noise goes away

Sounds like it is coming from the drivers rear

Loading the tires by swirving back and forth doesn't seem to cahnge the noise at speed

 

So if I didn't get the bearing in on that side just right(not enough torque let's say), wouldn't the loading of the tire change things and why would disengaging the gearbox affect that?

Why or would gear selection make a difference?

 

I'm thinking it's the diff and it's just has noisy gears. I ordered some high/impact redline and i'm going to change the gear oil-even though it's fresh oil.

 

Guys-I need some ideas or input. I want to drive this thing 1000 miles in a week and i'm getting nervous

[T-Bone028]

I think you should do as your planning, flush and fill the diff, add some LSD additive, and hope for the best. If you have time, flush and fill the tranny. May or may not help, but I cant imagine it would hurt to try some basic maintenance stuff first.

[JMortensen]

LSD only functions when turning. If this problem happens when he's not turning, that rules out LSD.

 

"Changing gears affects the volume of the noise." Hmm. That sounds like it might be a transmission thing. Diff and driveshaft are doing the same thing at a given speed regardless of what gear you're in. The transmission is the one that will be changing gears internally.

 

Usually if it is a wheel bearing the noise will change when you swerve left and right (should swerve hard when testing this).

[madkaw]

Isn't disengaging the clutch taking the load of the turning components even though they are still turning the same speed? Just coasting there wouldn't be the torque the driveline?

 

I will search this, but didn't I read that the halfshafts were all the same length regardless of r180 or r200. I was being told today that he thought there were two different lenghts of halfshafts. Someone want to clarify this????

[JMortensen]

U/J halfshafts are all the same length. CV halfshafts are different left and right.

[madkaw]

Okay, that's what I read Jon.

 

I know it's impossible to describe a noise , but it is like a

 

wha-wha-wha-wha which increases frequency with speed. I feel nothing! The noise sounds fimiliar in tone to the noise the diff makes during deceleration, but it has a frequency to it.

[MONGO510]

You have bad cluster gear brg's. The noise disappears in 4th gear because it is straight thru 1-1. There is no load on cluster in 4th.

 

IMO

Mongo

[madkaw]

Okay, what are considered cluster gear bearing-sorry don't know what that is. It sounds bad and I'm ready to take a 1000 mile trip.

 

And I said the noise is LOUDEST in 4th at 60mph

Edited July 27, 2010 by madkaw

[madkaw]

I will say that I had someone else go for a ride today, another z owner and him and I both got out of the passenger seat while driving and put our ears to work . I laid my head right against the floor in the hatch area(tire well is gone) and I am 99% positive that the noise is originating from the driver's side and loudest inboard towards the diff.

 

Well I'm going to bed so i can put in 15 hours on the car tomorrow to get ready for the trip. Please keep the ideas coming in guys.

[madkaw]

Getting desperate here, but is there any way a person can get the diff stub axles on the wrong side? I mean would the longer one fit in the shorter side and visa versa or would it be blatantly noticible

[JMortensen]

Could be a bad carrier bearing on the diff, or a bad inner CV joint. I don't really know how to diagnose a rear CV, fronts you crank the wheel and stomp on the gas and it will click at you.

 

You need to step back, stay rational, and try to reason this out. If you can't do that then either take the car to a shop or don't go to the car show.

[madkaw]

Sorry if I am sounding a little irrational, the time crunch is getting to me. At this point I'm going with it. It hasn't gotten any worse in the 500 miles I've driven it. I will try swapping diff next, but probably not before I go.

The U joints are fairly new and feel good.

[Tony D]

Leaving the Ann-Arbor/Detroit Junction on I94 my transmission which was making noise popped out of gear (5th).

 

I used a bungee to keep it in gear for the next 3000 miles (which was about 36 elapsed driving hours from there to SoCal).

 

For your short trip, I'd relax and figure it out later.

 

Oh, bring duct tape and a bungee, just in case!

[madkaw]

Thanks guys! I actually had the same conversation with a Z guy yesterday. Same deal-blown gear in the trans and he drove it for a couple of years that way!

[madkaw]

Well I made it guys. The noise never got any worse-or better with the redline gear oil. The car got amazing mpg and cruised great. I saw 80+mph plent of times and she was smooth. Thanks for the support for the worry wart!

[madkaw]

Well the noise is still there, but it didn't ruin a good time at ZCON. I did get back under the car and started probing around again. The only thing I found of interest is the tranny mount. It seems to give way too much movement. If I get under it and bench press the tailshaft I can move everything up and down a 1/4" easy-maybe more. With some gentle persuasion of a small jack I can lift the tailshaft an inch easy. Now I know that is not a jacking point, but the mount just seems way too sloppy. This was a newer mount that I modified to use the bwt-5 in my car. I cut and welded on this piece, but tried to be careful of the rubber-but maybe I still ruined it. How much is exceptable movement? I would think on hard acceleration that thing is moving close to an inch or more-but I haven't noticed any thing in the shifter. I will say that i haven't done hardly any hard driving with this car yet.

 

Could this movement be contributing to my noise? Hmmmmmmmmm!

[bjhines]

Bad mount= NVH, but you have another problem.

 

I have to go long on this one. Your tranny description really makes this tough, but it may shed some light. Vibrations are transmitted throughout a mechanical system. You may hear the noise from the rear left, but it's source may be the input-shaft bearing or input-gear tooth in the tranny.

 

Check my logic. 4th gear is worst NVH. 4th gear is straight through, input shaft is locked to output shaft. The other gears run on the counter shaft and are isolating the system(enough). The countershaft would completely isolate axial vibrations. Granted other v-modes will still pass through.

[madkaw]

Sorry BJ,

 

but you lost me with the NVH(what does this acroynm mean) stuff. In the beginning when I was trying to figure this out I called a shop that worked on diffs, but mostly trannies. He said that if the noise changes at all with shift changes, then the problem is the tranny-no doubt. That is sound logic since everything else behind it is turning a constant speed.

My contention is that the speed is the same , but the torque amount is not. That's why I thought the pinion angle made sense-especially seeing all the movement in this drivetrain. I'll admit I am way over my mechanical know how at this point-but it is fun learning!

[madkaw]

Well an update on this thread. I finally got around to replacing my diff with another r200-non LSD type and the noise is gone. The catch with this is that when i went to remove the halfshafts from from the car I noticed that I didn't get the nuts tight on the stubs. Maybe in haste to get the car together to get to ZCON I didn't tighten the nuts all the way? The halfshafts seemed to have beeen sitting flush against the stubs and I could't feel any play, but now I will always wonder if that played into the noise.

[madkaw]

I thought I would close out this thread because is does relate to my ongoing issues.

Using my recent discoveries of a bad halfshaft, I think I can safely assume that the shaft wobble was causing my whirling noise in the diff. I don't believe anything was wrong with the diff- though I had suspected sloppy side bearings. If they were a bit worn, the shaft just excentuated the issue.

I don't have too good of a memory, but I distinctly remember hearing while laying in the hatch area --what now makes sense as a worn shaft.

 

I know a lot of threads come up with these issues, that's why I am sharing my experience.