My rear end continues to make some loud noises, and i would just like to know some symptoms of the LSD gone bad, or is on its way...

 

rearends howl right before they die,,jack up the rear of the car,,of put down some water and try a burn out to see if there's posi,,you'll know
then

 

juss go to some donuts. thats wut i do to check if the car has lsd b4 i buy it

 

I was told to check was to jack up the rear end and turn the wheel on one side and if the other wheel turns the other direction then it is lsd. I think that is right and the donut trick does not work i have an 85 gs that leave perfect double donuts but is not lsd. but mine is wierd it also occasionall does posi burn outs. but then again it grabs right wheel some times. and if it hits posi in second it just luanches it cathes right wheel peel and it just lays it down for 20 feet. wierd if anyone gets any ideas let me know on that.

 

Is it a constant hum that seems to get louder?
It might be the U-joints in the driveshaft are worn out...

The rear end on these cars can take a good beating....

 

Actually, if the car is up and in neutral, e-brake released and spinning one tire results in the other tire turning opposite it is either an open rear end or a very weak/worn out LSD.

Some later viscous rear ends might trick you there, though. Same with some Torsen rear's.

Get one tire in wet grass and the other on pavement and see how quick you can accelerate. If it's open, the speedo may take off but you might not! ;-)

R

 

The actual, proper way to test a clutch LSD (which is the type first-gens came from the factory with if they had it) is to hole one wheel still and try to turn the other one. Easiest way is to jack up one rear wheel, chock the fronts, and leave the car in Neutral. It should be REALLY hard to turn, and then it'll "break away" and you can turn the wheel but it will still have quite a bit of resistance, although less than the break-away torque.

I don't have a Mazda FSM, but I've seen break-away torque specs for old Positraction units as well as Sure-Grips, and IIRC you put a torque wrench on one of the lug nuts, at a 90deg angle (meaning the angle: center of hub to lug nut to end of torque wrench) and the break-away poitn should have been about 40-50lb-ft or so minimum, just to give you an idea of roughly how tough it should be.

Back up in Cleveland we bought a 10-bolt out of a Caprice with Positraction, gonna put it in a slammed '57 Chev pickup custom/tow vehicle (not kidding!), and we used two 3' prybars in the lugnuts trying to get it to break away and we could JUST get it to break away (I'm around 190# and the other guy was, uh, "more", so we ain't sissies! ), and after it did it got about 50% easier to turn. Just FYI, of course RX-7 LSDs won't be THAT tight or the tires would slip before the diff would!

 

Jimmy I'm not sure if you remember me telling you how my car died but it was the initial result of my driveshaft. It ain't a pretty thing to see what it looks and feels like when your on the freeway and it goes out.
Hope you get it checked out handsome