Well here goes, I bought a slightly decent 85 gsl-se
four months ago. After fixing most of the little things
and making sure nothing was about to go,
one thing is still bugging me-"noise in rear diff"
I have fixed a lot of things on this car but this is
the hardest. I think it's the rear wheel bearing ;
I even took it to my mechanic and he seems
to think the diff is going, but still safe to drive.

So what to do? I can pull the diff If I have to.
He says the U-joints are not bad.

But the sound I have to admit, is not that bad
i.e. you can still talk in the car and most people
don't even notice it. It's not that loud.
But I do have play in the rear wheels
and this sound also disappears when you
pull hard on the emergency brake.
Wheels turn freely no binding.

Can you have any play in rear wheel bearing?
my car has some. Ya I know that the car has 185000k on it. So the rear diff is abit long in the tooth anyway.
So for sure my mech is probably right
in a way.

It did have the ring and pinion done by
a mazda dealer at 114000k
He said they my not have set it up right,

What can you do. Well I just might
try changing the rear wheel bearing.

Or get a second opinion on it
from another mechanic?

Thanks

 

Try swapping out the old 90W gear oil with Amsoil 75W-90 synthetic gear oil and see if it doesn't quiet down.

 

Are you sure they added the LSD friction modifier?

Whenever the diff oil is changed in a limited slip differential you *must* add the friction modifier or it will chatter.

It costs like $3 a tube. You could just put some in and see if the noise goes away.

 

Describe the noise. A whinning that increases in pitch and volume as road speed increases is a sign or ring/pinion trouble. Rumbling/grinding noises can be wheel bearings and usually can be figured out. Does the noise go away or change during turns? Or if you lightly touch the brakes while rolling?

Is there any vibration associated with the noise? Usually u-joints cause a vibration that can be felt. Oh and your 85 has NON replaceable u-joints. Doesnt mean they cant be changed, just means its a job for a driveline shop, not a regular mechanic. Your mechanic dont know what he's talking about. They are not a simple unbolt and throw in a new one.

Oh and wheel bearings cant be easily changed either. Requires a hydraulic press. If you need to do it, remove the axles and take them to a machine shop and let them change them.

 

Well I have changed the diff fluid I put in a 80-90wt
and lsd additive.
The sound is fairly constant. turning does not change
the sound but over bumps it does change.
it goes away when you some hit bumps
Its a metallic sound almost like brake drag.
Normal braking does not affect it.
But if I pull the parking brake hard at low
speeds it goes away
Thats why I think its a wheel bearing
bumps could be unloading it.
Same with pulling the parking brake

I does not matter what gear its in or whether
its accellerating or decellerating
clutch in or out.
The car has some vibration
but nothing crazy.

my mechanic just unbolted the driveshaft
to check that the u-joints were not seized
or binding says they are o.k.

 

Hey

I had the same thing...............But to my ears it was coming from the front........turned out to be the rear wheel bearing..........

 

Sounds like a wheel bearing to me. I had the same thing also, and like jimtesla said, it sounded to me like it was coming from the front as well. Then I really started to listen, which was easy 'cause it got louder, and sure enough, it was coming from the rear. It was definately a slight metal-on-metal sound with the added bonus of a low oscilatting rumble that was variable based on speed.

Brian

 

Thank-you guys for all your replys. It's been great help.
I went and looked over, drove the car today and crawled
under it again. Man the rear u-joint is gone!
my mechanic just does not want to break the
bad news to me lol!

Oh well now possible wheel bearings and u-joints.
and diff

I think that the u-joints are going to be first
thing I change. hope the diff holds out for
few more miles. I emailed and I will call
a place in town that replaces 'staked' u-joints.
So I will see what their price is.

http://www.euro-drive.com/

http://www.shafts.com/Merchant2/merc...de=MAZDA_STAKE

 

It's a 1985 5 speed the letters on the back says gs. I don't know if it is a gsl or se. I have a question. The fuel light is on. I was wondering if any of you know do I need to change the fuel pump or the float inside of the tank. Before you guy's start it does have gas in it.

 

It'll need a new in fuel sending unit. The sedning unit is about $110 and hopefully the screws aren't too rusted. Remove the cover immediately behind the drivers rear wheel (you'll have to get underneath for a couple bolts) and you'll see the sending unit. There are 3 prongs that go to the unit and usually one or more corrodes into dust leaving a constant fuel light or worse, a malfunctioning guage.

 

Do the ujoints, and if the noise is still these, put the rear axle up on stands, put in in forth gear and let'er rip a little to see if you can hear it and pinpoint which side.

 

errr, his post was four years ago, 84stock.

 

The low level fuel light comes on when their is approx 2 gallons of fuel left in the tank. If you are sure that you have alot more than this in the tank then there is a problem.

Most of the time the issue can be fixed by cleaning the corrosion on the electrical connections at the sending unit.

There is a test that can be done afterwards if the cleaning does not work.