Hi everyone, I have been experiencing what feels like a chattering or pull noise and feel when I make a full turn. It is coming from the rear and suspect it might be the differential or perhaps a wheel bearing. I have the GSL that comes with LSD and at first figured the noise was due to upgrading to front coil overs , rear lowering shocks/springs, and a racing beat sway bar recently as now the vehicle is much more planted to the floor. I don't hear a whine/whirl noise when driving straight or on the highway which is what i experienced when the diff was going out on a prior vehicle. Any ideas on what I should be looking for. Also, the previous owner was riding on blown rear shocks from what seems for a long time. I am wondering if perhaps the rear end might be experiencing suspension binding. I did not loosen the lateral arms etc. when i installed the rear springs/ shocks which is why I suspect this could be another issue.

 

I'd start with an easy test. Jack up the rear and check your wheel bearings. Side-side, and top-bottom play. Also rotate the wheels and check for excessive play with the rear end. Check the driveshaft joints too. That will pretty quickly source out any driveline related issues.
Suspension can require a little more due diligence since it's not as easy to statically replicate binding.

 

I had those exact symptoms with my LSD on my 83 GSL. This is probably the clutch pack chattering. I'd get it on turns and when just starting moving turning, launching after a red light.

I did a diff oil change with fluid that has friction modifier for LSDs and it diminished a bit but did not completely resolve until I added this exact friction modifier...

https://mazdatrix.com/product/oil-ge...-s-d-additive/

recommended by a forum member here. And even with the LSD special oil, I still had to use the whole container. This was a couple of years ago and no problem since.

 

Almost certain the LSD is the culprit from your description, and specifically that you hear it during cornering, as thats when the plate clutches are required to slip at their maximum. The GM friction modifier linked above is what I use, and you can't overdo it. Using the whole bottle and then adding 90w gear oil will almost certainly quiet things down again. Just changing the gear oil alone won't fix it. The LSD needs the modifier to work correctly or you'll end up damaging the plates by grinding them down. Report back,

 

A lot of GSLs have open diffs because the warranty fix for this was to install an open diff.

If a limited slip isn't barking, it isn't working.

 

Thanks guys, I just did a change on it recently (300 miles ago) with Valvoline 75w-90 that states it has "Limited Slip Additive." Should I top it off with the LSD gear additive or do a complete change with a heavier weight/ upgrade brand such as Redline?

 

Ha! That Valvoline is the exact stuff I used and it only calmed down when I added the friction modifier linked above.
Edit:
Drain or suction some of that fluid out, add in the whole bottle of friction modifier, and then top up with what you drained out. Don't overfill.

 

Better info... It was back in May 2024 when I had the chatter, and I changed from the Valvoline to Lucas 80W90 plus the friction modifier

https://www.rx7club.com/1st-gen-gene.../#post12602608

 

So you cannot just top off the friction modifier? If it requires a drain and refill, maybe it might be best to get something high end like Redline or Amsoil that already come with friction modifiers? Either way, the kid that owned the car before for 3 years did zero maintenance so the Valvoline stuff can probably serve to flush out the gunk as the gear oil was super dirty when I drained it.

 

Also, the local parts store has Royal Purple 75w-90 and 75w-140 on sale. Would this also be a good choice to replace the Valvoline Synthetic 75w90 (+LSD additive)?

 

My experience was that even though I already had friction modifiers in the gear oil, I still needed to add the additional friction modifier from the link, the whole container.

You want to fill with the proper volume to the factory spec, which is when it's just starting to dribble out of the fill plug as you fill.

First make sure your fill plug opens, then the drain plug and empty the entire contents. Since you are replacing the fluid, pour in the entire bottle of friction modifier first, then top up with the new gear oil.

I don't know about those other oils that you mentioned, all I know is that when I replaced mine with the Lucas 80w90 and the entire bottle of friction modifier that my chatter went away.

 

Thank you, I will start with the friction modifier first and then explore the other options with Redline, Royal Purple, Amsoil etc. as those have worked great on my previous cars. Redline has always seemed the best performing IMO.

 

Buy two bottles of GM friction modifier - you'll eventually need it with the next gear oil change. In the meantime, if it were me, I'd just drain a bit - add the CORRECT modifier - then refill to the proper level with new gear oil (*the same as what's in there now). Not all friction modifiers are the same; the GM additive is the only one that works with the Mazda OEM LSD.

 

Thank you all for the help. Great news…chatter is now gone! I ended up buying some CRC Trans-X® Posi Trac Limited Slip Gear Oil Additive from the local parts store. I liked that it came with a cone tip to allow easy pour into the differential. After reading positive reviews online about this; I decided to buy it and add a tube. My commute is 45 highway miles so after getting into the city; I noticed the chatter was gone when making turns from a stop. 😁👍