2004 RX8 6 speed
137,000km
Driving style - Very Hard

I looked at a few threads that didnt really give me an answer on this problem . My car sounds like there is a "whine" comming from the rear diff and it is not the tranny . When im cruising on a strait stretch and the drivetrain is under load there is no sound , as soon as I let off the gas it starts to "whine" . It does not matter if im in gear or not in gear , or if the clutch is pressed down or not so we can rule out tranny noise and throw out bearing . It gets loader as I go faster (again no noise under load) and the noise slows down with the car . It does not sounds like a wheel bearing to me so Im thinking it can really only be.

- Tranny output bearing
- Pinion bearing
- Pinion/Ring gear mesh noise

Im curious if this is a common problem on higher km's RX8's ? Car has seen track time and im not easy on the rear diff and has also had some 8k clutch drops on it for some closed course fun .

Any thoughts on this and wearther someone makes a good aftermarket gear set (mabey chromo ?) .

 

clutch wont affect tranny noise since tranny always spins with the rear diff.
and you said doesnt matter in gear or not so thats probably not tranny internal gears more like output shaft bearing and the stuff after.
although there are some combinations you can rule out if the sound is front the input side of the tranny. in gear clucth in/out, not in gear clutch in/out.
when did you change diff and tranny oil? you might try the cheap stuff first.

 

Thanks for your reply ,

Yea the tranny is always spinning , I did not word that quite right . Yes I did change my tranny to redline , and the diff to synth . I took it out for a drive today and suspect it is the output bearing becuase it sounds closer to the gearbox . The only thing that throws me off is the sound is like an off/on swith with the throttle , as soon as u take ur foot off the gas it starts . I feathered the throttle off rather then just dropping it and the noise does not feather in with the throttle , it just gets to a pinpoint and starts which isnt really a characteristic of a worn bearing . When I park the car and put the tranny through a wide range of rpm it does not make any sounds , its only when the car is under load so it has to be output or further . Just a tough one to try to pinpoint while its on the hoist .

 

When was the last time you changed the differential fluid?

 

prolly a couple months ago , going to be changing it out today .

 

did the problem occurr before or after the change?

 

Put the rear end on stands. BE SAFE! Get a helper and a mechanics stethoscope.

http://www.amazon.com/Lisle-52500-Me...9601468&sr=1-1

Have the helper bring the drive wheels up to a speed that you can hear the noise then while he is able to duplicate it, crawl underneath and listen for the noise using the stethoscope as help to pinpoint it. Don't want to sound obvious but watch out for the rotating items: driveshaft & rear axles. Use the stethoscope around the rear diff, the rear wheel bearings, and the transmission output shaft.

Again, BE SAFE! Or just take it to a local mechanic and have them diagnose it for you instead on a lift

 

Im not exactly sure when it started but I can say its winthin the last couple months , so after . I had AP with cat delete and got sick of it so I put in a cat which made it about 40% quieter and thats when I started to notice it .

 

Yea it will be in my friends shop hoist's, im gonna try this today accualy . I was just curious if there was a more common problem or not .

 

whining is not uncommon problem with manual transmissions. my S2 makes a high pitch whine in 4th gear when on gas, also it makes a even louder when in 1st gear when decelerating.
could it be the shifter boot is broken and passing transmission noise into the cabin?

 

If the noise is in the rear end/diff its the pinion/gear mesh. Basically the lash is off/gears are worn.

 

tranny is fine , rear end toast . its not gone but had some decent chunks on the magnet and we got a few more with a smaller magnet inside pumpkin . My guess is the chirping when you launch when the rear is fighting for traction , and first to second shifts when it gets hoppin . Mazda where I live (Vancouver B.C.) quoted me on ring&pinion alone was $668 . No side bearings , no pinion bearings so call it almost a $1000 all set and done with new seals and all . Might just try to hunt one from a wrecked car . Throw one back in and see how long she goes for again ! Your not having fun if your not breaking things , these cars deserve to get DRIVIN ! Nothing like holding a tight sweeping corner in 2nd at 9,500rpm and launching out into 3rd and really start moving . All on closed course of course

 

That's my vote. Diff parts are pretty cheap from Mazda. Setting lash is a talent. With that many miles and assertive driving you should look at the entire drivetrain. I'd look at the exhaust manifold and condition of all four ABS lines (about 2-3ft in length). When the ABS fails in these cars it is ugly. UGLY. UGLY to the point of scarin the crap out of you. I've had ABS fail at Daytona and hit the wall left of the bus stop hard. Needless to say I gave the car back to the owner and never stepped in it again. Another thing I'd look at with high mileage is the half shaft boots and the front caliper pad wear. The front calipers flext and we throw them away mid race season. You will see this in brake pad taper from the front calipers opening permanently. The rear wheel bearings are near bullet proof. The fronts should be replaced. They too are cheap and contain the front ABS unit. We run new front hubs at the beginning of each season also. If these hubs overheat they are prone to ABS failure. This is seen as 300+ mph via the OBD port.

 

Thanks for the reply , it was the diff after all and the new one should be in today that I got from a wrecker for $400 with 80,000km on it and car had front fire damage so drivetrain is in good shape . We are going over the whole drivetrain as we speak , one front leaky crank seal so far ... no biggie and thats about it other then changing all fluids and checking bolts and plugs and lines and all that fun stuff , no leaks in maniford and everything has been re torqed. I dont care what I have to do to the car really becuase its like a sport to some of us , just like my rock crawler (you think an 8 is alot of maintainence try rock crawling) But I love these cars and everything about them and still love the fact that it runs like the day it was bought from dealer and its got 137,000 HARD driven km's on it . The weight balance is just tops in this car , from the rear suspension to the kicked back motor for a near perfect balance . IMHO the people who accualy drive these cars and not baby them get better life out of the motors from what ive seen . You just gotta spend near the same as a new motor replacing hubs bearings seals and fluids haha .

 

Hope I can do this as well. My car is making the same exact noise as you have described. Should I as a novice mechanic uh wannabe car fixer, attempt this?

 

It wasnt THAT easy of a job , even with full shop , hoists and everything . I wouldnt wanna do it in my driveways thats for sure . have since dropped a ls1 with 300zx rear end in , couldnt keep the stock diff together .

 

Well I just found this tread and was glad to see it was not-just-me.

I had the same problem on my 2005 and 2008 RX8s... both were bought new... both developed the whine after only 1K miles... dealer said it was a gear lash noise... normal !!!

I thought the 2005 was a "bad one" so I waited a few years before getting the 2008.

I loved both cars but had to get rid of them before 5k mikes because I could not take them on a trip... the no-load whine noise for a 10+ hour drive was more that my wife or I could take. My wife kept checking her cell phone thinking that it was ringing.

I tried Amsoil rear end lube in the 2008 to no avail... so it's not just a problem limited to high mileage / hard driven RX8s.