Brassmonkey

iTrader: (2)

Hey guys,

I've done a bit of searching but didn't come up with an answer to this question. My car is a 1986 GX, with a TII swap (engine, brakes, transmission, driveshaft).

When the vehicle is in motion, I hear this low "thwum thwum thwum" kind of sound, that is very periodic. As I accelerate, the sound speeds up as well, and changes pitch slightly. I'm pretty sure it's not engine related, as I will get to a good speed and coast, and the sound remains the same. I'm also pretty sure it's not brake related, since I will brake hard from a good speed, and I can still hear the sound.

So, I'm thinking that it has to do with the drive train; perhaps the driveshaft or one of the axles is out of alignment, causing this off-center sounding noise.

Any ideas?

Thanks,

Dan

unren

iTrader: (3)

you might wanna check your wheel bearings. i slid into a crub and both of my right side wheel bearings started making that noise. i can really start to hear it at ~30+ mph.
if you are gonna check em, just push(hard) in and out on the left and right sides of your wheels and the top and bottom. (looking straight at the wheel) if there is any noise or movement, its probably your wheel bearings.(also could be a tie rod or ball joint on front wheels.)

nofords

iTrader: (9)

my 88 GX does that because of the rear u-joint in the d-shaft

jake1191

iTrader: (1)

Check the stuff in this order

1. Wheel bearings
2. CV Joints(dont forget to release the e-brake)
3. U-joints in the driveshaft

it is most likely the wheel bearings. Especially if it feels like what many call fast rumple strip which is basically what you decribed

jake1191

iTrader: (1)

oops double post

pfsantos

iTrader: (1)

See what happens while coasting or holding speed while turning on a long bend...see if right or left sounds different...the weight shifting during the turn will change the sound if it's your wheel bearings...if so check your wheel bearings.

Puck

iTrader: (1)

If you changed out the driveshaft, make sure you tightened the bolts on the driveshaft to rear end flange. Don't ask me how I know...

Brassmonkey

iTrader: (2)

Thanks for all the input so far, I will look into the wheel bearings first.

Is safety a concern right now? If I do as pfsantos said, would it be unsafe?

Gene

iTrader: (1)

If it's indeed the wheel bearings and they are making as much sound as you seem to indicate, then it could be a safety issue. OTOH I drove my old eclipse with a whoom whoom whoom sound for probably 30k miles. I wouldn't drive it on the track that way though :p

The front wheel bearings on these cars suck for whatever reason. I have to tighten the nuts on my fronts maybe every other track weekend. If they're not too badly shot you can generally get away with just re-tightening them. Check the FSM for the procedure.

MazdaMike02

iTrader: (4)

Thats because you don't lock the nut to the shaft by hammering the nut into the slit on the end of the shaft dude.

Anyway check the rear wheel bearings, put the car on jacks and in neutral. Spin the wheel with one hand and put your hand on the spring and feel for vibrations its extremely obvious. Its the better way of checking for a bad wheel bearing because sometimes they don't have any wheel play. CVs will click when turning and when straight if really bad. U-joints on the driveshaft will hum and click just change them anyway its easy.

Brassmonkey

iTrader: (2)

Sounds simple enough, I will try to take care of this on the weekend.

When you refer to the univeral joint on the drive shaft, which part of that is replacable? The section that bolts to the differential?

MazdaMike02

iTrader: (4)

Both sides are. Snap rings hold the caps in, take the snap rings out and use a press to press out the caps and then get the ****** joint out. Its really easy just you need the right press use a ball joint press.

Brassmonkey

iTrader: (2)

So I finally got around to doing something on the car last night. I've got the back end jacked up, and when I press on the top of the wheel, there is play. That is to say, I can 'wiggle' the tire back and forth. I took the wheel off, and the whole wheel hub (rotor and all) has the same play. This doesn't seem right...

Is this what you were referring to? Does this mean the bearings are shot, or is it another problem all together?