My current car:
'87 S4 T2
dyno'ed at 177 at the wheel
also have KYB 8 way adjustable and poly bushings


So my problem:

Look at the picture, see the crack, my differential/driveshaft (at the connection of the two) would bounce up and then down, causing a bang sound. After inspection I noticed the crack between the two nuts that hold the subframe hindge to the differential. My question is what could have caused this? Body flex? Too much power? (177 isnt much). If its any of those issue's i'm sure someone else would have had an issue with this.

The most logical explanation is the bushing that is on top of the subframe keeping the differential/driveshaft from bouncing, broke. If so, how would i remove this?

 

That's just a broken diff mount - REAL common problem on all 2nd gens. Power is not an issue - I'm fixing to replace one in my near-stock '86 base.

It's a pain to install a new one - you have to drop the rear subframe and differential out of the car. I highly recommend getting the competition diff mount - about $80 from mazdaformance.com. BIG difference with the comp mount.

Dale

 

Hey Dale, you can replace the mount without entirely dropping the subframe, just loosen the driver side pull it down a little and then you can get to the two front diff mount bolts pretty easy, so then you only have to drop the diff and carrier.

 

Hold on, arent all of these mounts welded on?


So far I have removed the subframe and now I am looking at the cracked hinge or mount i guess, right???

 

The mounting shafts are for the diff carrier and the sub-frame, but that is the only part. You leave those alone anyway, other than removing the nuts.

 

I belive he is saying the braket on the subframe cracked or broke.

same thing happed to my car after I replace a bad diff mount, the bracket on the subframe actaully broke off, after inspecting it I have come to the conclusion that the metal was weak and rusted, bought a new subframe, haven't put it in yet but when I do I'll make sure to paint it with an anti-rust paint.

I can take a pic of my spare subframe if you want so you can tell us what piece actually broke on yours

 

Hmmm, never seen that bracket on the sub-frame broke...

 

well once I have some time to change out my subframe, i'll show you my butchered bracket, broke 2 time and got it welded back together both time, now I'm back at square one, the bracket is still intact just thrashed.

 

what was the condition of the diff carrier mounts??? was the rubber all shot to heck???

 

Well it happens. (check out pic) Thank you by the way to BlackRx7 for understanding what i'm talking about. My sub frame bracket broke and I just removed the differential mount and it is bad also.

I got a Sub frame off of a 86 na at the junk yard. What can I do to prevent this in the future. BlackRx7 you mentioned something about a anti rust paint. Whats a good brand and where can i get it. And do I have to sand it down first till the metal shows clear?

Cool gonna have my baby back in less then a week, already ordered the differential mount from mazdafomance a competition one (btw same as the Mazdatrix's one except $ 85 instead of $110) Just want to make sure this doesnt happen again, I appreciate the lesson of taking apart the rear of the suspesion but dont wanna do it again. :O


Thank you, Sergei

 

heh my subframe braket is prolly 10 times as ugly as that.

about the anti-rust paint, I'm not sure what this stuff is called my dad has, its a more like a hard plastic coating, specifically designed to stop rust. This paint actually bonds to the rust, just as long as its solid and not loose, I plan on paint my differntial cover with it too.

All you have to do is scrap of all the lose rust with a wire brush and paint it on, I'm pretty sure its not a spray, so you have to utlize your paint brushing skills

 

yep, that is pretty nasty:


But I still have to wonder, what the diff carrier rubber looks like. I would think with the front mount that wasted, that the diff carrier mount's rubber would be all cracked and broken up as well.