Loud roaring noise rear end?

[petere]

Hi all,

Big fan of the site and have searched and found loads of info, amazing what people have are willing to share on a forum!

Our 1987 tercel has done just under 300,000km and has starting making a roaring noise from the rear end, especially noticable on the highway, this can then be split into to 2 seperate noises:

Noise 1 - constant never changes - assumed to be wheel bearings

Noise 2 - by shifting into 4wd the noise 2 dissapears and then re appears when I switch back into 2wd - I assume this is either the diff of some tailshaft or transfer case issue? sound is very loud

Any suggestions on the cause of the noise would be greatly appreciated.

I was thinking about replace the rear wheel bearings and speaking to a mechanic about removing the rear diff centre etc so I will only have a front wheel drive tercel as I rarely use the 4wd function anyway - can this be done?

Cheers
Peter

[Mattel]

I'd say rear wheel bearings, don't pull the diff unless you try this first and noise does not desist. I am not sure about the 2wd/4wd quandary though as that should not make much difference, so perhaps it may be driveline? How long since the bearings have been done? some good synth oil in my rear dif has reduced a small noise I was getting from there.

[keith]

Find a lonely road and then do some swerving to see if the pitch changes. If it does, that indicates wheel bearings. If it does not, it could be a bearing inside the differential or a U-joint (or two).

Sometimes a tire can really roar too.

[Petros]

Worn out rear wheel bearing are pretty common on high milage cars, sometimes if it is bad enough you can raise the rear wheels, trans in neutral, and turn the wheels by hand and feel the rough bearings. They will roar louder with higher speed and power loading does not make much difference in noise. Wheel bearings tend to roar whether in 4wd or not, and go with car speed, diff noise can go with power loading so there can be little to no noise unless you are in 4wd.

Wheel bearings are not too hard to do yourself, you remove the rear axle half shaft and take it to a shop and have them press off the old bearings and press on the new one (be careful not to damage the seal in the axle housing when pulling the axle). If you have access to a press you can even press them off yourself. You will know for sure it is the bearing once you can hand turn it directly, it should be smoothly rotating and tight. Should be about $40 per side. The rear diff is pretty durable, unless you run it dry it is not likely to be worn diff carrier bearings.

Does your trans and front diff oil level full? If it is low it might cause the noise, hopefully it is not too late to top it up.

The front wheel bearings or the half shafts with 2 CV joints each can also act like this, when in 4wd you are not driving through the front axles alone taking some of the stress of of them, reducing the noise of worn bearings or CV joints. Typically if it is the CV joints, they will be louder when you accelerate through a turn, and they would also make a rhythmic thumping sound. Front wheel bearings will roar with speed and turns make little differece. These, like the rear, must be pressed out of the hub. It would save you money to dissaseemble the front hub and have a shop press out the old bearing and press in the new one, rather than have the shop do all of the work.

If you have a self service wrecking yard near you (Pull-A-Part, Pick-your-part, etc.) you can just go get the hub assembly, and even a rear axle assembly, with the bearings in them, and swap out the whole assembly. Way cheaper than new bearings. If the front axle shafts have good boots they are work getting too. I would not replace any of these parts unless you know yours are bad. You can reliable tell if the used parts are good by rotating them by hand, should turn smoothly and be tight, no binding, grinding or roughness (not even a little), and they should be good.

if your front diff bearings are shot it might also act this way, but this is pretty rare unless you ran the front diff dry.

First thing I would do is change or top up all the gear oil in the front diff/trans/transfer case and the rear axle. One you get the rear axles bearing fixed isolating the other sounds might be easier.

I would try to isolate the noise before I made any major repairs. Let us know what you find.

Good luck.

[toughtercel]

of course , the wheel bearings , pull out the rear axle shaft ,turn the bearing by your finger , feel funny that the problem , i replace them alots , like " petros" say they are common ,very common , when order parts " beaware" , half of the time i order bearing WITHOUT "inner retainer so far only place find complete kits is at the dealer and price reasonable . so that in Canada so i dont know about you fella

[petere]

Thanks for the replies,

The CV's have been replaced recently and are pretty quiet, but the rear wheel bearings have never been touched.

This week I'll try check off some the items mentioned -

- first the basics check oil levels/ top up etc
- swap one of the rear tyres over as it is pretty old (still legal) but might be making some noise - will also see how the wheel bearings feel with the car up on a jack
- replace the rear wheel bearings

Will let you know how it all goes.

Thanks again
Cheers
peter