gerpacar

Have a 1990 GXL with Automatic tranny. Recently starting hearing a single clunking noise on takeoff and deceleration sometimes. Noise usually happens at slow speed, <25mph. Read a lot about loose rear differential mounts on this site. Everything appears tight underneath with car sitting on ground. What's the proper way to check the mounts? Is it the 2 wide mounts at the rear of the differential everybody's talking about? Any other suggestions about what it might be?

nonameo

driveshaft u-joint... check that.

mac_dad6

im not sure how to check them. they basically work the same way as an engine mount and if the rubber part break the differential will move and thump on the bottom of the floorpan. i thought this what what was wrong with my car but it truns out the differential was just toast and it blew up 2 days later

Madrx7racer

ouch.......how much did it cost to fix/replace?

BTW check the U joints and mounts....as nonameo said.

nashman69g

iTrader: (3)

I seriously doubt the U-joints are bad as you would be expriencing a lot of vibrations out of the car...I am willing to bet you your rear differential mount if broken...they will go out just like your motor mounts...after 14 years of use they tend to go bad esspecially if you put a lot of stress on it...When I had my auto (Now 5speed) mine broke...Now to answer how--You will need to drop the subframe assembly and then you can get to it....This is PITA ...And also the mount costs about $135 for the stock on or $110 for a competition one(stiffer) from mazdatrix! Good luck!

silverrotor

iTrader: (1)

The Differential Mount Is classic when characterised by a clunk to the rear. Raise It up and confirm this. Our cars are noted for this Mount breaking.

87turbo2

rear end mount. I've broken several. This sounds identical to that.

fg0d

It is the CV joints if these cars have any.

87turbo2

Cv joint? NO. The rear differential's nose has a mount that wears out or will break all together sometimes. This is heard as a clunking noise in the rear of the car under initial acceleration or deceleration. Just drive down the road and let off the gas and you'll hear it. RB or mazdatrix has the replacement mount, they run about $90 US. Or if you want to make it stiffer it can be welded in place.

gerpacar

Once "raised", how do I confirm it's broken? I've already looked at it, and from the outside all the rubber appears to still be there, although looking old and dry. With broken motor mounts on "normal" engines you can usually see the cracked rubber, which I didn't see here on the 2 mounts holding the differential up. Should I be able to detect "looseness" with the rear end jacked up?

Thanks for all the replies!!

twistedriver

Wow i didn't know abuseing your car can blow up your diff mount! I think i broke my diff mount. My quetion is how long will it last before the whole thing falls out? THnak you have a good day!!

1987RX7guy

iTrader: (3)

Sounds like a broken front diff mount.


Santiago


PS- I have one used in good condition PM me if you want it.

silverrotor

iTrader: (1)

Here Is a broken Differential Mount -


For additional Info, look here -

https://www.rx7club.com/showthread.p...hreadid=271688

I also posted an additional link In the link above for ***** out permanent repair.

twistedriver

IS it safe to drive the car with a broken diff mount? Will the whole thing just fall out or damage other componets? Thanks you !!

razorback

would this noise come from around the mid engine area?

PHATFC3S

like everyone else said check the diff. mount get under the car and actually inspect it. check it for cracks in the metal piece and check the bolts and make sure the rubber piece of the mount is still attatched.