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Rear Diff dying? (roaring noise)


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13 replies to this topic

#1 EastCoastEJ22T

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Posted 16 August 2008 - 10:34 AM

Just bought a 1996 2.2/4eat legacy last month and in the last 200km the car has developed a loud roaring noise from the rear end. It sounds like a really bad wheel bearing, but i jacked the front and rear and checked the wheel bearings and they seem fine. The noise comes on at around 60 and gets louder as speed increases up to about 110, when it seems to start to fade again. I removed all the heat shields and checked the u-joints they are fine there is some play in the center/ carrier bearing, but nothing drastic. I tried driving with the 2wd fuse in, no change. I've done the torque bind tests and no problems. It's just making a crazy amount of road noise. Front diff levels are fine, and when i checked the rear diff levels i removed the top fill plug and fluid came out!! I assume the diff was over filled by previous owner/mechanic, drained and refilled but the noise is still there.

Any input or info is much appreciated, or if any one knows of a test for the rear diff, other then the torque bind test. Thanks alot.

(canadian car 290000km dealer maintained one owner)

#2 Reveeen

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Posted 16 August 2008 - 10:50 AM

The "easy stuff":
Rear backing plates @290,000K they are rusty and maybe 1/2 gone.
If a posi the rear tires HAVE to be the same diameter (check with string)

The not so "easy":
The wheel bearings are roller bearings, the ONLY way to check them is pull the axles, and hubs (unless they are blowed up)
@290,000 the rear U joint has play in it
If the car has been jacked up on the body side of the rear trailing arm make sure the bracket isn't bent negating the rubber.
Check the rear sway bar and mounts.

That's all I can *think* of.

#3 EastCoastEJ22T

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Posted 16 August 2008 - 11:20 AM

thanks for the info, I'll check the backing plates when the rain slows a bit(good old Nova Scotia weather). I didn't know they were roller bearings, hopefully thats what it is, cause thats what it sounds and seems like it should be.

#4 Reveeen

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Posted 16 August 2008 - 02:50 PM

hopefully thats what it is

The wheel bearings on your car, like mine, require a special tool. It would be awfully nice to put the bearing carrier in a hydraulic press, pushing the bearing in, and out, but you will distort (bend) the carrier. I'm pretty sure you could use a piece of hardened threaded rod, and a couple of machined up washers to draw the new bearing in, otherwise it is a dealer only operation. Don't forget the seals, one inner, one outer with each bearing. (seems to me that 2 seals and one bearing are about $75 locally (aftermarket), or at least that's what I recall paying)

#5 EastCoastEJ22T

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Posted 16 August 2008 - 04:15 PM

Thanks for the tips. I work as a aircraft mechanic and have access to a full machine shop, We have tooling made to change aileron/elevator bearings the Rod/cup/press type. I think i'll just order a bearing get some dimensions and make up a set up out of 6061 stock.
We also have a few presses for building up landing gear/flight control hinge fittings, that are soft jawed and have brass dies, but i'd rather not tear down the whole rear end just to change two wheel bearings.

by the way jacked up the rear and checked the drum backing plates there fine, sway bars fine, and the jack points front diff support mounts and tabs are fine. But there is definately drag in the Driver side rear wheel bearing. We use alot of roller bearings on torque tube/ flight surface actuators, and the bearing feels heavy, and nothcy? (hard to explain)

is there a procedure in the service manual for changing them on the car,
I have a download of the 96 SM, but can't seem to locate it.
or do you know what side of the bearing carrier the bearing is pulled/pressed from. (inbord face or outboard face)

Trying to type and watch CORR truck racing at the same time is proving to be difficult. :D

any more info/ideas is appreciated.

#6 Reveeen

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Posted 16 August 2008 - 06:11 PM

is there a procedure in the service manual for changing them on the car

Ok, well, I don't have a service manual, and I don't own a car with drum brakes. So, with a rear disk set-up, you gotta get the axle out, so, with the wheel on the ground, crack the axle nut (loosen), jack the car up, put on stands, take off wheel, brake stuff (rotor and caliper, I would assume drum) take nut off of axle, and remove the two strut bolts, This will let the carrier move enough to pull the axle out (flop the carrier towards you, push the axle back on the sliding joints) The hub should pull (maybe a bit of tapping necessary) out of the bearing. The bearing goes inwards. Now because the hub rides in the bearing check CAREFULLY the surface that the bearing rides on. New hubs are approx $120 (dealer only). Clean up the carrier (where the bearing goes with emery cloth) and carefully install it with oil to help it slide in, pulling it in place with the tool you made. Install everything you took off.

I am not familiar with your specific car (year and drum brakes) it might be necessary to remove the bolts holding the diff in to get the axle out, mine comes out as described.

#7 aircraft engineer

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Posted 16 August 2008 - 07:16 PM

Just bought a 1996 2.2/4eat legacy last month and in the last 200km the car has developed a loud roaring noise from the rear end. It sounds like a really bad wheel bearing, but i jacked the front and rear and checked the wheel bearings and they seem fine. The noise comes on at around 60 and gets louder as speed increases up to about 110, when it seems to start to fade again. I removed all the heat shields and checked the u-joints they are fine there is some play in the center/ carrier bearing, but nothing drastic. I tried driving with the 2wd fuse in, no change. I've done the torque bind tests and no problems. It's just making a crazy amount of road noise. Front diff levels are fine, and when i checked the rear diff levels i removed the top fill plug and fluid came out!! I assume the diff was over filled by previous owner/mechanic, drained and refilled but the noise is still there.

Any input or info is much appreciated, or if any one knows of a test for the rear diff, other then the torque bind test. Thanks alot.

(canadian car 290000km dealer maintained one owner)


you might try looking at a junkyard - those rears are pretty much interchangeable in that time frame. It's a LOT easier, of course, IF you find drum brakes since almost all ot them seem to be DISCS. You will STILL need to disassemble the entire rears and take out the unit hopefully with the entire strut to save aggravation later on.

actually pressing out the hub and changing the backing plate from disc to drum is pretty easy - particularly if you work on planes. the hardest parts are the axle nut (32mm) and that &^^%^%#! LINK at the bottom the HOUSING (19mm and an absolute BEEATCH to get loose because of the close clearance) piece of cake otherwise (remember to buy new grease seals and IF you disassemble the hub to pull the tone ring put more grease in the bearing. ALL of the factory units were BALL BEARINGS - the rollers are "aftermarket fix" - like was said easy insertion/removal. If you use "pre-owned" parts) it may or may not be a roller bearing. The roller bearings supposedly hold up better.

I have to do at least 1 on my IMP and I'm not necessarily looking forward to the job (it IS kind of messy)

BTW - get a mechanics stethoscope and determine which side is "bad". From a practical standpoint, while it takes longer, you might save future aggravation by doing "both". The replacement ball bearing is $70 US or so. The JY unit was $40 US each, so it might be a better deal IF you want to go strip a donor car

rears remove and insert from the OUTSIDE (the snap ring is on the OUTSIDE - under the HUB) there are articles about it online GO HERE: http://forums.nasioc...ad.php?t=787070 with pictures too It's for FRONTS, but it's pretty much the same as rears except that the bearing go in from the OUTSIDE inward

#8 BoostedBalls

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Posted 17 August 2008 - 12:47 AM

I would feel the hubs in the rear after a good highway blast. Try to coast to a stop, using the brakes as little as possible. Then if one hub is warmer than the other, I would tear into it. Stupid car dealerships like to pressure wash cars to make them look newer. In some cases, they blow water past the seals in wheel bearings, ball joints, etc; this eats the parts from the inside out.

If you don't feel any difference in temperature, I would replace the carrier bearing and replace the gear oil in the rear. If the gear oil is nasty, I would use something synthetic and maybe a little thicker than recommended. Stick with LSD oil if so equipped.

#9 EastCoastEJ22T

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Posted 17 August 2008 - 09:52 AM

1. I going to change the diff fluid this moring to a synthetic 75W90 and see if that changes anything, it's a cheap and easy test so why not.

2. I'll check the bearing temps Monday morning on the ride to work 30 min all highway, with lots of room to coast to a stop.

3. I'd be willing to strip a donor and swap new bearings into the donor carriers/ then just swap the carriers. I'll have to wait till monday and make some phone calls to see if i can find one with drums. I have a 1992 touring wagon (EJ22T) for parts at my parents farm (4hour drive) but it's got disks and i don't know if the carrier is simmilar in design or not, maybe i'll get the old man to take some pics to give me a better idea.

Thanks for the nasoic link pretty informative, i'll update in a bit with any changes.

Any one know how much play is allowed in the driveshaft carrier bearing?

Changed the fluid, made no difference, i'll check the other ************ later.

Thanks for the help so far.

Ian

#10 johnceggleston

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Posted 17 August 2008 - 12:21 PM

it would be a fair amount of work just to rule out the drive shaft carrier bearing but you could put in the FWD fuse and remove the rear section of drive shaft. this would leave only the wheel bearings and the diff turning.

#11 EastCoastEJ22T

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Posted 18 August 2008 - 03:08 PM

Ok, so ran some temp tests with a infared digital thermometer today.

After running at 110 kmh for 15 minutes all highway i coasted to a stop no breaking and took a reading for the wheel bearing carriers.

FL-112 F
FR- 110 F
RL-108 F
RR- 132 F(the worst)

Reardiff 118 F

This does not seem that bad to me, with the amount of noise coming from the rearend, i figured one bearing would be Blue hot.

ANYway i'll try and drop the driveshaft/carrier bearing tonight and see if it has bad play/ temp issues( it's hard to tell on the car because of the rubber bushing it sits in)

IF no play is found in the steady bearing, i'll change the RR wheel bearing.

#12 hohieu

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Posted 19 August 2008 - 12:02 AM

How did you check the bearings? I had a rear right wheel bearing making noise for over 40K miles before I replaced it, and there was never any play or perceptible roughness in the wheel when turning it by hand. I could feel roughness in that corner only by placing a hand on the coil spring while rotating the wheel.

As mentioned by AC, removing that lateral link bolt is the toughest part, especially if you live in the rust belt. The rest can be done on-car if you have Hub Tamer type tools.

#13 BoostedBalls

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Posted 03 September 2008 - 01:14 PM

That RR bearing seems like a problem to me, especially if you have aluminum wheels. They will pull the heat out faster than steels.

BTW- the driveshaft will ALWAYS spin if the car is in motion. Regardless of the fuse for the transmission. It is directly connected to the spider gears in the rear diff and then to the tires.

You could remove the driveshaft and clock it 90 degrees out from original to see if the noise and vibration changes.

my $1 is on the wheel bearing though.

#14 EastCoastEJ22T

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Posted 04 September 2008 - 03:10 PM

FIXED.... left side rear wheel bearing. Didn't have the time to do it myself. 2 hours labour plus $120 canadian for the OEM subaru bearing/seals x 3. The place who did it had a hub tammer and did it on car. Car now runs butter smooth and quiet....very nice. I could not beleive the deafing amount of noise the bearing was making. Thanks for all the input and help.
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