ratboy

iTrader: (1)

I did some rear end work on my car this weekend upgrading the suspension and trying to figure out the cause of a sound my car is making. At cruising speed I can hear what sounds like a rubbing noise coming from the rear of my car (whup, whup,whup,whup....). I thought wheel bearings or brakes rubbing but when I jacked the wheels up and spin/shake the wheels I dont get any slop or noise. I came accross a post where someone described a similar sound and said -->ujoint. I noticed my drive shaft rubbing on some heat shielding so I bent that out of the way but the noise is still there. So my question is how do you know when a u joint is bad (wasnt loose or sloppy that I could tell)?

-Erik

BTW I plan on replacing my wheel bearings after I rebuild my spare diff and can get that ready for my car.

racintang

I would just spend the 5-10 bucks and replace it anyway. At least you can eliminate it. If it shifted you would know, just a little bit off and it will vibrate from spining outside of the centerline. I would also check the transmission bushings to to see if the whole thing has moved. It shouldn't be rubbing on any sheetmetal unless you hit something.

BMS2004

bad news ratboy you have to buy a new driveshaft if yours is bad. 83-85 had non-replaceable u-joints. My front joint was bad and after removing it i'm lucky it didn't explode on me causing some pretty bad damage. In my case under any kind of load it would make a "eeeee errr eeee errr" type of sound.

Best thing to do is jack up the car and remove shaft and move yokes to see if they move freely or not. Hard to diagnose with it still in car.

ttrider

you can get the u joints replaced. so not bad news. I have a 1985 and I just had mine replaced. Just go to a shop that does u joints and find one that will mashine it for you. They have to mashine the olds ones out and put the new ones back in. Make sure you find a shop that knows what they are doing. If they dont you will have to end up buying a whole new drive shaft. Cost me $180 canadian but mine were completely baked. I got everything replaced except the actually drive shaft its self. Good luck.

BMS2004

http://www.mazdatrix.com/g9.htm
see top disclaimer.

If you found a shop that did then sweet maybe I'll try that. I was just under the impression that nothing could be done.

pinkfloyd

ya i was told by people that i could not replace mine, but i took it to a place that did it for 85 bucks and that was with new u-joints and moding it so i could hookup a T2 tranny with a NA rear end, this was on my 2nd gen.

BMS2004

hmm thanks guys, you saved me $240 or whatever for a new one, guess I should cover up the old one this winter! =) Thanks

ttrider

ya np...I got mine done at a truck equiptment shop that sells like cranes and they do driveline for large trucks. They did an awesome job and hopefully that solves all my rear end troubles.

sixtydgree

You're right, although I had an 82 about six years ago and that had a Driveshaft/u-joint combo too.

Keep in mind that if you have that driveshaft machined with new u-joints (no matter how good the person is) you run a serious risk of the metal being weakened. Do screw around with your life, if that thing snaps you have a chance that it will find somewhere under the car to lock its self into and it will feel like the breaks were just slammed on and the back end will lock up and the possibilities from there are grim. Just be safe about it and replace the driveshaft.

bliffle

If you hear a new click or clank when you startup and have a strange nasty vibration at roadspeed you have a bad UJoint.

The rx-7 UJoints are actually replaceable, tho the shop manual says to replace the whole propshaft ($450 OEM from mazdatrix, or $250 aftermarket). The UJoints are only about $20 and you can actually do it with hand tools IF YOU KNOW HOW. You can also screw it up. I have a spare propshaft that I got a couple years ago that's going in this week.

B

racintang

bench vise, socket and a wrench is all you need.

rx7owner

I think you wrong because i replaced my Ujoints on my 83

bliffle

plus big hammer, punch and internal CirClip pliers or dikes if you're hardup. Can't do it without a heavy bench vise, tho.

SevenHeaven

Your right... I replaced teh driveshaft on my 85 almost 3 years ago. I looked into the idea of replacing the joints themselves but decided against it. For my piece of mind there was too much risk of vibration and sudden failure. I still use my car on the occasional track day so for me safety is a huge deal.

Like others have said there are good people out there who can do the job properly. I just didn't want to find a bad one!

ratboy

iTrader: (1)

My car makes the sound whether the transmission is engaged or not but it still sounds like the u joints form the posts of others (I have the occassional loud pop when putting in reverse in the AM). Should I stop driving the car or will I be OK with "whup whup" until it turns to "eeerr eeeee"?

Looks like I finally get to make that big mazdatrix order Ive been putting off....

thanks -Erik

Whanrow

Where abouts do you live? I'd like to source a place nearby that can do them.

Its very interesting to hear all the stories that they CAN be replaced. A friend of mine works at a heavy truck driveline shop. They have replaced some rx joints, and without fail have found the driveshafts impossible to perfectly balance. They will do it for you for about $250 cdn, but they do not recommend it as there will always be some degree of imbalance (read vibration) no matter what they do.

There was a guy here on the board a few months ago that replaced his by himself, and finally gave up a bought a new driveshaft beacsue he was so unhappy with the results.

bliffle

Interesting. the Haynes manual recommends using a set of variable thickness CirClips to get the centerlines coincident. I never had a problem with other cars, but that was a while ago. I plan to transplant an extra propshaft I have that I pulled from a rolled SE a couple years ago: it appears to be in excellent shape.

Mazdatrix has an aftermarket propshaft for $250 that might be good. But the problem remains of balancing the new propshaft against the old trans and diff.

SevenHeaven

Bingo!

I've hard the same stories. I also know some guys who make custom shafts and they said the same thing. From my research the Mazda part is the best one out there, thats why there is a Mazda driveshaft on my car. On a side note a friend of mine has a Mazda dealer (has been since the beginning of time) and he was saying that at one time the U-joints were replaceable on earlier cars. But they always had vibration issues with the replacement joints!

bliffle

Hmmmm. Makes a guy think. I'm still gonna put in this nice looking SE propshaft I have. I was just wondering if I oughta take it to the neighborhood guy or go underneath myself. These days I like to have someone else go under.

ttrider

ya im in langley B.C. and replaced them fine and shop knows what they are doing. They are right next store to a mazda shop and do some of the rx 7 u joints for them.