Rear end sound(s)

[SVOJames]

My 116K mile 86 has developed some strange sounds, and since I can't troubleshoot worth a darn, I'm turning to you folks.

First sound, it's a "whine", a high pitched type sound. Mostly noticeable at 60 mph +. It's not road sufface or tires, because if I depress the clutch, the noise goes away (or lessens, anyway, kinda loud exhaust).

(It's not the turbo, I know that whine, and this noise even happens coasting down hill)

Second sound is kinda of a "grinding noise", not like rocks thru gears, but maybe salt?

After about 20 miles of 65+ highway driving, the center of the rear wheels was almost to hot to touch, and you didn't really want to press your hand down.

brakes binding? low fluid? wheel bearings?

Any suggestions for tests or such?

TIA

[svobud]

both of them sound related to the rear differential.

I would suggest popping the pumkin cover off and taking a look at it a bare min. Sounds like you need, at least, is change the fluid. Ya, know..if you don't change that stuff on a regular schedule - it can turn to thick putty? Worse case - as you may have done some serious wear on your gears from running it like that is...you're gonna need a new set of gears/shims.

btw, that deep/low 'whine' you hear....is usually called a "howling" rear gear...

[KevinK]

sounds like axle bearings need replacing. Probably not too expensive. Some are pressed on the shaft. Not sure what the 7.5 or 8.8 have. You can pull the axles and have someone press new bearings on. Some slip on and others are set into the housing. If I'm opening a rear end with >80K miles I would replace them. The right oil does wonders too.

[gbeaird]

Yep, check the axle bearings. Both sounds may be sourced there.

Get the back end of the car up on jack stands, pull both wheels, pull the shifter into neutral, and go turn each axle by hand. If the bearing is going out, it will sound and feel rough as you turn them.

It could be only one bad one. I seem to remember the diff on our 86 whining a bit when the passenger's bearing went out. After things warmed up, it sounded like I have gravel in a hubcap on the right rear. Everything got replaced, and the diff filled with some fresh Red Line, and everything's been quiet ever since.

Gene Beaird
86 2R SVO
Pearland, Texas

[svobud]

DOH!

I forgot about checking the bearings!

[cobra0478]

I believe Bud was closser with his first post,you did say the diff. housing was heating up a bit.
Catch the oil in a clean container when you drain it & look for metal particals.Post back with your findings.

[SVOJames]

Now I know what I'm doing this weekend, thanks for the pointers.

Watch for another post from me in this thread, I'm giving 5 to 1 odds it'll happen.

[SVOJames]

Ok, wheels off, the driver side takes a _lot_ of effort to turn (break-over bar across the studs), and seems to bind about half of every revolution. Might be the brakes dragging, I don't think so, but I don't have an allen head (hex head?) wrench that fits the caliber pin, so I haven't pulled the caliber. Any one know which size I need?

Passenger side turns by hand, takes a little bit of effort, but doesn't require a break-over bar to turn, and doesn't have the binding the other side seems to have.

Looks like we have 2 bearings on each rotor. Will I be able to look at these and determine if they are bad, or should I just replace them anyway?

If the hub binds, but after removing the hub, the axle rotates freely, that indicates bad wheel bearing. If the axle still binds after the hub is removed, that indicates bad axle bearing. Is this basically correct?


========================

Got the pumpkin cover off, fluid wasn't putty. I don't _see_ anything wrong, no shiny spots on the gears (had someone rotate the wheels slowly while I looked). Of course, this is the first time I've seen in the inside of a diff, so I don't know what I'm looking for. Anything I should look for, or should I take pictures and post them here?

Now, when I go to button the rear-end back up:

What fluid do I use?
I need a "limited slip diff" additive, right?
Is the Red line fluid stand alone, or is it an additive also?

Lastly, how the heck do I put the fluid back in? I can't find an opening/drain plug.

Again, thanks in advance for the replies, and for the help given so far.

James

[SVOeric]

ok , I'll try to help a little.

first off, when you turn the left wheel, the right wheel should turn also (and vise-versa).  If you only had one wheel up in the air at a time, this may be what your binding was ???? (posi-traction rear end)

there is no drain hole on the rear, but there is a fill hole.  it is on the front of the differential, and use a 3/8 ratchet, with a short extension to remove the plug (with no socket)

there is a lot of good differential grease out there.. i would recomend something synthetic.  I run mobil one in my rear, and mobil one synth ATF in my trans. -- whatever you use, you need to put the friction modifier in it (nasty smelling stuff too!)

as far as the bearings go, you have no bearings that you will be able to look at, unless you pull the c-clip (in the center of the differential) , and all the brake hardware off the car.  then you will have to pull the axle, and as I remember the bearing  is about 6 inches away from the hub (and there is only one per side).  these bearings are pressed on (not like a wheel bearing) and you would have to have someone press it off, and a new one on.  about the only way to check them is to pull them out, and roll them, and inspect them. (while still on the axle)

 

If you've never had a differential cover off before, here is how you get it to seal back up (without leaking) get some black silicone RTV, after all surfaces are cleaned, run a bead around the cover, dont put a ton on it, but a healthy bead (it will squish out of you use too much) -- let it sit that way for a few mins,(about 5) until it starts to get firmer, then put the cover on, and tighten all the bolts about finger tight, let it sit for at least a hour ( most of the tmie, i let mine sit overnight) , and then torque it to specs, and fill it with fluid, and all should be good.

 

 

[SVOJames]

Both wheels are off the ground at the same time. I wondered why I didn't feel the binding on both wheels, considering the limited-slip, but thought it might have been the slippage that is inherent in the system.

Since I'm this far into it, should I just pull the c-clip and get those axle bearings replaced (along with the wheel bearings)? Pulling the calibers isn't a big deal, it looks like I just pull the clip and slide the axles out (and back in) - I don't have to mess around with the stuff the book tells me to "leave to a professional"?

Thanks

[SVOeric]

I would pull the axles, and check the bearings.  just roll them, to make sure they are smooth, and look them over good.  I'm wouldn't replace them unless necessary.

Just unbolt the 4 nuts from the axle retaining plate, that holds the axle in, pull the c-clips, and the axles should pull right out (sometimes a little coaxing is required)

With the back of the car jacked up, You should be able to turn the axles by hand, and when you turn one side, the other side should turn in the same direction as well.  Get those brakes off  there, and eleminate that as a source of binding.

If you are getting that much bind, and only on one side I would almost think you may have a bent axle.  How long have you had this car, and have you ever slid the rear wheels into something sideways ??

 

[svono50]

Whoa Eric, hold on. The 7.5/8.8 rears do not have the bearings pressed onto the axles, they are pressed into the housing, so you don't have any bearing retainer plate to unbolt. Just thought I would clarify that before James starts unbolting things that don't need to be touched.

To pull the axles all you need to do is pull off the calipers/rotors, pull the differential pin (or at least push it out of the way of the c-clip), push in the axle to get the c-clip off the axle end and then pull the axle out. On the end of the axle tube will be a seal and behind that will be the bearing (roller type).

Another thing to check with the axle out is the surface of the axle where the bearing rides. If it is pitted your axle is pretty much trash. You can go with "axle saver" bearings, but I would suggest getting new axles. The axle saver bearings move the bearings out further to ride on a virgin part of the axle and have an integral seal. I thought they were the best thing since sliced bread, until I went though 3 defective ones that had bad seals. How fun is pulling your axle 3 times in as many weeks.

Anyway, it sounds as if your bearings are trashed, hopefully your axles are fine. Good luck and keep us updated.

[SVOeric]

he is right.., too many rears I have worked on since my SVO.  (namely my truck)

When I was typing that, I was trying to remember which was which, and I thought I had it straight.  -- SORRY!

[svono50]

Don't worry about it, I wasn't trying to flame ya, we all make mental errors...I should know.

[SVOJames]

Ok, got the calipers off, turns out that's a 7MM hex key on the caliber pins.

One of the caliber pins needs to be replaced (hex portion is stripped). Is this going to be hard to find a replacement for?

I'm stuck getting the rotors off. I've removed the caliber, and the outside break pad. My Chiltons tells me "remove the rotor retainer clips and the the rotor". I can't find the retainer clip. How does this rotor come off?

Eric, I've had the car 8 years or so, and while I've been sideways in it, I've never hit anything (knock on wood).

TIA