Differential growl/rumble
 

I'm hearing a low growling or rumbling noise that sounds like it is coming from the differential (this started about 2000 miles ago). It only happens after I have been driving on the freeway and then get off and make sharp turns like in a parking lot. I'm thinking since the car is hot, the oil is thin in the differential, and the gears are noisier. Just a guess.

The thing that worries me is, I had an old RX-7 with a 100K + on it and it had what I remember to be a very similar noise problem only much louder. It was scarey to drive it over 80MPH.

My current RX-8 is a 2004 automatic with 10K on it. Does anyone know what the cause of this is? I've heard it's normal from a couple people including one of the technicians at Everett Mazda and also from the guy I bought my old RX-7 from. Thanks in advance for any info y'all can provide.

Could be the dynamic stability/traction control systems activating -- that can feel like a rumbling. Try disabling the dcs/tcs and retrying the maneuvers. CAREFULLY, of course....

I've got the same exact noise/experience. When first starting out, slow-speed tight turns (like parking lots and driveways) are quiet and smooth. After about an hour on the road (could be less, don't know), I get the same groaning during low-speed tight turns, especially if I'm under power (i.e. in first or reverse, maneuvering for a parking spot). I was also suspecting heat in the LSB causing some additional LSD action/binding, but it seems to be louder than normal. Mine is a 6sp, with about 34K miles.

Anyone have any answers?

(I found this thread while searching, so I might still find an answer as I sort through the search results.)

lug nuts retorque?

Yes, the lugs are properly torqued. The sound I'm getting is NOT the clicking/snapping that would occur from the lug nut problem. It is a more-or-less continuous groan - like an old-man trying to get up out of chair - during tight low-speed cornering.

Try to swap out your gear lube in the differentail and inspect it for metal shavings when it comes out. Next refill with Redline 75W-90. You will need two bottles of the redline and a manual hand pump. You can get to the drain and refill plugs easily on the rear differential.

I thought my rumble/growl was the differential too.

It turned out to be a bad wheel bearing (RR) at 40,000mi.

I can confirm that this is indeed the DSC/TCS. https://www.rx8club.com/series-i-trouble-shooting-95/grinding-noise-when-cornering-50535/

This is not the same as the problem I have. Mine is whisper quiet on any/all low-speed curves etc. when cold. The noise/groan only occurs after long drives - like 45 minutes to an hour or more, at highway speeds. Then, the noise is there during low-speed tight corners. It is proportional to the differential action - i.e. the repetitive nature is faster with tighter turns, slower with less-tight turns. Obviously, also vehicle speed dependent.

You could describe the sound as similar to the sound of an old car, cranking with a half-dead battery (rrunh-rrunh-rrunh-), but coming from the rear.

Oh - and my noise is there with and without DSC/TCS.

I don't believe I have ever had a noise coming from the rear diff, but I did replace the oils in the tranny and diff at 16k miles and the factory stuff was pretty burned up looking. Replaced with Redline oils and have been just the same if not better ever since. I am at 27k now.

What happened? Have your resolved this issue?

In my case, the dealer consulted Mazda USA, and they recommended a full synthetic gear oil for the diff, and that took care of the low-speed groaning when hot.

^ These are very good news. Can you please mention what brand and type was your synthetic gear oil?

What about Gord? Did he solved the problem with full synthetic gear oil?

Sorry - they didn't tell me which synthetic brand they used. I can check the receipt, but it'll have to wait until Friday (I'm away on business now).

The sound you are describing sounds more like a bearing noise than anything. The groan of a worn bearing. I would consider changeing the fluid in about another 5000 miles and see if you have any particulate matter (metal) in the new oil. Also trhe drain plug is magnetic so look at that also. Just changeing to a synthetic oil might have made the noise go away for now due to better lubricating properties but the problem might still be there.
Keep an eye on it.
I think I am one of about 3-4 people that have had a diff put into there car. Mine would not make any noise as you are describing but rather it would shudder. If you stopped and turned the wheel all the way in one direction, then drove away. Like you are just takeing a sharp right/left turn. The rear end would shudder. The tech confirmed it with the DSC on and off. Pulled the drain plug on the rear end and got a pan full of metal. I own a 2005 AT and this happened at about 4900 miles.

Today I just changed my differential fluid and I put Red Line 75W-90. The problem was gone ! In addition we saw the drain plug and there was almost not metal at all.

Now the differential is very quite at any slow turn.

I will keep in mind your advice Easy_E1 but I guess that your problem was different than my problem. You had a shudder I was hearing only some noise when starting.

Glad it had no metal on the drain plug and sounds better.

Well, I would like to ask you couple of things now that I have solved my problem.

1) How many miles have you done free of problem (noise) after you have solved the problem?
2) Why we needed to change our differential fluid in order to solve the problem. I mean why the differential fluid from factory was not providing adequate lubrication?

What was the vehicle mileage in each of these cases?

^ I had 17.000 Miles but with hard driving.

Mine is starting to make a noise from the rear area, similar to the diff clutch chatter. I changed the rear end fluid at around 45k with red line, and I am near 59k now. I am going to check the fluid again to see what it looks like and if it solves the problem. I hope so :)

I'm having the same issue. Only happens when I've been driving awhile. I know it's not the DSC/TSC because I have the base model which does not have that. I have ~14K miles on my car and will have the dealer look at it in a couple weeks when it goes in for it's 15K mile service.

I was having the same issue. I took mine to the dealer but i couldn't get it to make the noise. On my next service appointment it made the noise after they did the service and i was able to let the mechanic hear it. Now i am getting a new rear end for my car. The mechanic didn't even put the car back on the rack. He went to a computer station and 5 minutes later he said you need a new differential. Either good service or part changers..... who knows.