I'm getting a large amount of vibration from the drivetrain that literally sprang up last night. There wasn't any instance that I know of causing it, it was rather a case of "hey wait, what's this?"

The shudder is most noticeable between 10 and 20 mph (especially during decel), after that it smooths out as the frequency increases, but it's still easily felt through the stickshift and, to a degree, the seat. It is speed-dependant, and seems to have no relation to engine RPM or transmission gear. In fact, there is no difference between being in gear (clutch in or out) or neutral. Revving the engine parked in neutral is smooth as butter.

Sounds like rear drivetrain to me--driveshaft u-joint, differential, or half-shafts. What has me confused and seeking opinions is how quickly the problem popped up, and the fact that there isn't any accompanying noises like the clunking or thunking you get from a failing u-joint. The entire drivetrain is being replaced in the swap, but in the meantime I don't want to be driving on something that could make for a catastrophic failure.

Anyone run into this before?

 

I believe shuttering on decel is caused by bad rear u-joints. I would wait for conformation first.

 

does it alsso happen around 60mph?? check your Ujoints for play and DO NOT WAIT TOO LONG TO FIX IT or you might end up with much more damage.

If not the U-joi9nt then check your suspension componenets, steering, wheels, etc. etc.

what have y ou checked so far???

 

That does sound like it's the driveshaft. Unfortunately the U-joints aren't serviceable so it's not a cheap and easy fix. It is an important one, though, as failure can break the transmission housing or, well, anything else around there it wants to break.

 

You have some options:
1. get another STOCK DS (used or new)
2. www.mazdatrix.com has some rebuildable DS I believe.
3. Go to a local shop and have them modify your DS with rebuildable U joints.

 

Mazdatrix has a few choices to go with. I opted for the aluminum DS. I am very happy with it. Just make sure you get the right one. If you have changed anything in your drive line other than factory, let them know. I.e n/a with T2 tranny etc. etc...

 

Nothing. It's 25 degrees outside with the windchill, and I'm more of the athletic type. I can't even think straight in that temperature let along figure things out under the car.

Around 60 it feels like mild back massager, but is still part of a progressive change with an increase of speed and isn't marked by any spike in intensity. I'm guessing whatever's vibrating is around resonance at about 10-20 mph.

I doubt it's steering related because vibration through the steering wheel is minimal, the vast majority comes through the stickshift. It's a completely different feel from normal, if I wasn't completely familiar with it from always driving one-handed I'd still be wondering if it was just my imagination or a slow-building exhaust leak.

 

ouch. Well don't drive on it unless it's an emergency because like we said, if it breaks you WILL see a lot of damage. I've seen the damage it caused at 25mph and I'd hate to see what would happen at hwy speeds.

 

Figured as much, I've already called out from work indefinitely. I think I know a couple people with replacements, but better to be safe than sorry. At any rate, I'll know more when the sun's up.

 

junkyard for a temp fix in case you need to go to work. You already checked the regional forum?

 

OK, an update. I have some play in the driveshaft, but it's all rotational. In the u-joint itself there is only a couple degrees of play (again, zero play in the "jerk your arm around" directions), but in the differential I'm getting about 10 degrees of driveshaft rotation that translates to no movement on the half-shafts. CV axles are solid with barely distinguishable rotational play, much like the rear u-joint on the driveshaft.

Edit: Haven't lifted the car yet to let it idle in gear and eyeball things again, but if the diff being shot turns out to be the problem, I'm probably just going to go with replacing the fluid with Heavy ShockProof from Redline. It'll make what's left of my LSD useless, but I'm thinking there's not much left at this point anyway. It only has to last another month or so before the TII train goes in.

 

it may not be the u-joint itself but rather where it mates to the driveshaft
I had a hairline crack in the weld that wouldn't show unless the drivetrain was under load while driving - had a helluva time finding it even after the shaft was pulled from the car, needed a friggin magnifying glass to see it
from your description you may have the same exact problem
and unfortunately the only solution is getting another driveshaft

 

If you had a hairline crack that only gapped under load, then you shouldn't have had any problems unless you were under load. But as I said, I can be slowly coasting in neutral at a human running pace and be getting a shudder. Still, I'll grab a magnifying glass when I jack the car up...

 

Here's a little story i'd like to tell and it goes a little something like this...

I was in Cary NC visiting a friend and when i was going to Cary Town Plaza I noticed my car vibrating... No biggie, except the fact that I live in Tallahassee FL. Well I made a few calls and the advice i was given was don't even think about driving back to FL with vibrations or i'm going to end up on the side of the road with a busted DS... Low and behold I put in a replacement DS and made it back to FL. Just for kicks I removed the new DS and put the old one back in just to drive around the city with. After 2 days this is what happened... Not Cool... I was at the mall going uphill and all of a sudden I heard a loud snap then metal dragging and well yeah... check it out...




Goodbye Drive Shaft... lOl

 

Awesome. I did the same thing in my CJ-5 flooring it up a 45-50ish degree incline. Put a big dent (made up of a lot of little dents every time the shaft swung around) in the floor behind me. While that was hilarious, I really wouldn't want to see anything like that on an RX-7.

But the examples I keep getting are all for cruising speeds, not crawling. Did any of you get the vibration at very slow speeds, if you can call about five shakes per second a vibration.

Hate. Cary.

 

If your diff's shot it'll make a weird noise when turning....its u-joints dude.

 

mine were at crusing speeds. Redundant vibrations from failing U-Joints...

 

While odds are it is something like the ds u-joint, just for ***** and giggles you should have the tire balance checked just to eliminate the obvious...and if they fixes it great : ) Other that check the obvious like bad suspension components and wheel bearings.

 

I spent today and yesterday replacing my front suspension and the driveshaft. While I didn't think the former was the culprit, I figured "eh, might as well knock it out while the car's off the road." Ironically, getting the damn forward bushings out of the control arms took longer than anything else. Trying everything from setting them on fire, drilling, torquing, devulcanizing the rubber, and various combinations thereof, the only thing that finally got them out was crossdrilling out the center fitting and then blow-torching the rest out. Bleh.

Anyway, it was the driveshaft afterall, but again (as always) not quite what I was expecting. All of the u-joints were tight, but one of them was a little too tight. One of the pivots on the forward u-joint is completely locked up, and all effort's I've made to free it have done nothing. It looks centered, but even if it's perfect there's a reason it needs to flex and I'm sure that was the cause for the problem showing up at any speed. Every half-turn it must have been giving my transmission a little shove. That would have been an express method of destroying a rear tranny bushing.

Either way, the replacement is in and all is well. Back to work. Thanks for the help guys.

 

Just out of curiousity... I thought that although Mazda produced a driveshaft that was not to be "serviced", that you could replace the U-Joints

http://www.rotorwiki.com/index.php/R..._FC_Driveshaft

I've never done it myself, so I really wouldn't know.

 

I'm in the process of replacing my u-joints for a stock shaft right now. Rockford Driveline (www.rockforddriveline.com) make replacement joints. Order two of those and this is what's required.

The stock joints are held in the yokes by a little lip, called a stake. The factory basically puts in the joints and uses a press on the end t press in these little notches that push over the top of the bearing cap, on all 4 ends of the joint.

Get a heavy duty grinding disc made for a dremel and cut that lip off. Don't worry about cutting into the old cap, as those joints are history anyway (although try not to because the hardened steel will wear down your disc).

After you can fully cut off the staking lip, beat the **** out of the other end using a socket just small enough to fit the cap. This is the hard part, I'm still trying to get it out. But supposedly, once the staking is gone, the bearing cap and joint should eventually poke out the yoke enough so you can grab it with pliers and pull the cap off.

After the joint is removed, grind out the spline in the yoke ear hole so you have a smooth, round surface in there. Put in the new joint and attach clips.

Now you have a serviceable u-joint.

A shipment of two joints is about $52-54 delivered. Much better than the $$$ new shaft, although you may not have the time fr all this. I'm fortunate because right before this problem occurred to my car, I bought an old Subaru for the winters here in snowy NY. Now I have until spring. I'm taking some high res pics of this process as I go. I'll try to post them so you can see what I'm talking about.