Uh oh, a blank thread. Quick, someone close it.

~T.J.

(Somehow this didn't get uploaded...)

I'm not the most mechanically-inclined, so I'm sending up an SOS here....

Got an '84 RX7. She's developed this outrageous shudder when on the move (higher the speed, more intense the shudder) emanating from the back end. Local mechanic at the dealer says it's the rear axle, that there's a loose fitting inside that cannot be adjusted and that the whole thing needs to be replaced. I'm not exactly buying into that theory just yet.

I've read one or two threads here on the subject but nothing that really addresses this particular symptom.

Any ideas out there....?
Many thanks in advance.

-Branch

bring it to a transmission shop, they deal with driveline problems on a daily basis.

Check the U-joints on the drive shaft near the rear end.

Check for rotten-arse old tires that have a radial belt broken. That was my problem. I mean it shuddered horribly, right at 70+.

Now, it shudders because the front U-Joint has about 1/4" of play in it. Mazdatrix to the rescue, new driveshaft next Thursday.

It could be shuddering because of out of balance tire/rim.

jerij

:withstupi
Take it to a shop and get them to balance and aling everything for ya. It could jsut be that a weight on the rear tire came off and is now off balance. Even if that doesn't fix the problem its a good thing to have done to your car and also not horribly pricey either. Especiall yif it saves you form having to get a new rear end!

i had the same problem! the transmission place told me it was the diff!!! but fortunalty it turned out to be the Uni joints in the driveshaft!!!

My 84 does something similar, but my tires and driveshaft are in good shape. Does it more at low speed. I believe it's a combination of weak springs/struts, worn clutch packs and a sticky bearing in the real axle. Sometimes, if it sits for a few days, it will CLUNK when I take off.
Anyways, good rears are hard to find for 1st gens. The parts to rebuild would cost around $250 from mazdatrix. Not sure on labor. I wouldn't say it'd cost too much if you drop the 3rd member yourself and take it somewhere. $100 maybe? If you're junkyard savvy you can find some replacement gears like from a b2200. I've always wanted to try that...

jayroc, when was the last time you changed your diff. lube?

Big Thanks!
 

Thanks to all for the responses.

I'm not the best person to be under the hood (or under the rear axle for that matter). Been taking it to a dealer (...hold your boos & hisses please...) and they're the ones that said I needed a whole new rear axle.

I like the additional ideas.

Can anybody recommend a good shop in the mid-peninsula area that can do the work reliably?

Thanks again!

-Branch

I changed it when I got the car about a year ago and used Mobil1 synthetic. Didn't help.
I heard LSD additive would probably help, but I'm too lazy, and it's my second car, so.....

jayroc
I've had 6 diffs and I can say now, you need a new diff if it clunks occasionally, it's not THAT much of a problem... yet, but the clunk will become more common as the car ages (Loose diff pin)

And anyone know how to remove the kangaroo effect when decellarating? Like idle mixture? Or something?