Possible diff problem?
 

This has started recently, and has gotten worse. I don't know what might have caused it, since I do get on the gas often, but I've never actually launched my car ( for the specific reason that I'm scared of breaking something ).

What happens, when the car is cold, I'll be pulling out of my parking spot or the apartment complex, I'll accelerate from a stop as I'm turning, and while I'm slowly letting the clutch out, I get a vibration/jerking motion from the rear of the car. It sure strikes me as similar to what people have described when they lose teeth on their gears. Of course, this only happens when I'm driving from a stop, and after a few minutes it will go away completely.

The length of time that it takes to go away has started to increase. My first idea that the diff fluid needs to be changed since it goes away after the car has warmed up a little, and I know diff fluid has to warm up to get decent lubrication. And I also assume its the diff, since it only happens when I'm turning. Anyone able to pinpoint the problem exactly?

Blake

Changing fluid may help, but I don't think anything is wrong with it. Mine acts the same way. Go to "How stuff works.com" for a good explanation of differentials work

Sounds like your PPF may be cracked same problem Im currently having. Or Bushings little by little are getting worn out.

PPF?

I know how diffs work, the problem is the fact this has just started happening recently, and continue to gets worse...

Blake

Power Plant Frame, dont feel bad I didnt know the intial either until last week. If you hear the differential "hopping" like a thump that may be it.

Did you add limited slip differential additive the last time you changed your differential fluid? If not your differential will stay locked up in sharp turns and make the back end chatter.

The third gen diff is a torsen. It does not require limited slip additive. Limited slip additive or friction modifyer is normally only used in clutch-type differentials.

I disagree. Page A-16 of the 1993 workshop manual says "On vehicles equipped with limited-slip differential, API GL-5, SAE 90 special lubricant is required for limited-slip differentials". Also I changed my rear diff fluid with gear oil that didn't have the LSD additives once and the back end chattered around sharp corners. I switched to redline 75w90 which does have the additive and the the chattering went away.

It shouldn't matter, I haven't had the diff fluid changed in a long time, but that should be something that would show up pretty early after the change. I might just change it, but I don't want to spend money changing it if its something much worse.

Fatman, I know what the ppf is, never seen it abbreviated though. I don't see why that would go away when it warmed up though.

Blake

I have the same problem, but it doesnt happen all that often.

Mine usually does it when I am doing a sharp turn reversing out of a parking spot.
I recently changed my diff fluid to neo synthetic and it helped the problem some, but it still remains sometimes.

I have 86k on all my stock bushings, so my pushings may be on the way out, or my PPF is crackes somewhere, who knows.

diff bushings are more than likely the culprit. that and most anything is going to be a little rough until it reaches decent operating temps. buy a kaaz and you'll wish you had your current noises :) check you ppf for any cracking and maybe invest in some new diff bushings

k, I'll take a look. Is there any way to tell if the diff bushings are bad by looking at them? How hard are they to replace?

Blake

the stock ones have some nasty, milky looking fluid in them. if they're bad, it'll usually be a little wet on top of the diff and you'll see remains of this fluid on the bushings. to replace, you have to drop the diff down at least a few inches, and take off the diff mount. then it's a matter of pushing the old ones out and pressing the new ones in

Ah, doesn't sound too bad. I'll take a look at them. I was looking at rotaryextreme and rx7store and didn't see and replacement bushings. Do they make improved aftermarket ones, or should I stick with Mazda ones?

Blake

any aftermarket ones are going to be quite noisy. i have pettit solid bushings. other than the fact that they were different sizes when i got them. after rigging them up to work right, they eliminated a lot of slop, but i can hear the rear end whine like crazy when i'm decellerating. i personally would stay away from the pettit, just because of the experience i've had with them, but there's a few options out there. you might be able to find someone with a set of Jimlab's diff bushings for sale