legokcen

iTrader: (8)

With the interior pulled recently I'm hearing a lot more sounds from the RX-7 than I had been used to. I've had it completely stripped for about two months now and I have a question about what I'm hearing.

When I'm on the gas (light, steady, hard, doesn't matter) I get a higher pitched whine coming out of what seems like the rear of the car. At the same speed cruising steadily, I don't hear it. And it's gone when decelerating. It's only present when I'm on the gas. Any idea what it could be? I have a GSL Rear going in the car soon so if my drive shaft U-joints or rear diff are going, I'll be changing those. Any help would be appreciated on the whine.

Thanks.

81gsl12a

iTrader: (1)

my 1st rearend had that same noise... kinda sounds like the gears are tight (cant remember if its tight or loose that makes the noise)..in the end it went KA-BOOOOOMMMMMMMM

change the gear lube to something good.. and dont be as hard on it.... if its your track car swap that other rear end in it....the rear end you are puting in it is from a 84 or 85?

legokcen

iTrader: (8)

I'll change the fluid in the rear ASAP. Are one side of the gears worn which makes that noise or is something broken inside?

Rogue_Wulff

Probably more related to the age/miles on the rear end, and the gear oil inside it.
If the car sat for a long period of time (1-2 years, or more) without being moved, the exposed areas of the gears/bearings could have gotten some surface rust on them. This is especially true in a very humid climate. This can lead to a little noise that likely wouldn't be noticed with the rear carpet/insulation still in place.

max924

I have had this noise occur when the diff gears are not properly adjusted after being put back together- and it was REALLY loud, almost unbearable to drive the car, but unless you tore your diff apart lately that may not be the problem. The noise in my case was caused by the teeth of the gears not aligning properly when mating and when you let off the gas the pressure comes off the gears-thus no more noise. This was in a 924 transaxle.

If better or thicker lube doesn't quiten it you may want to check the gear teeth clearances.......

A little side note -- apparently an old trick to stop trannies from grinding when you were selling a car was to fill it with bananas , supposedly it would quiten it for a while! i wouldn't recommend trying it though!!

Max

max924

I forgot to mention that if the gears were worn that would cause the gears to go out of spec

rotornoob

iTrader: (2)

another thing to check is the rear wheel bearings. mine is making the same noise but i know my wheel bearings are bad in the back. sometimes that can make a humming noise on accelleration. on decel you might now hear it until they are really bad and on coasting you also may not be able to hear it

thirdtimesthecharm

I have a similar whine. I just purchased the car two days ago after a new driveshaft had been installed. Along with this whine I notice that there is a pronounced clunk coming from the rear if I abruptly take my foot off the throttle. Could this be play in the diff or u-joints?

rotornoob

iTrader: (2)

third : im not sure that the driveshaft u-joints will make a clunking sound when they are bad but you will notice a lot of vibration coming fromt he rear/center of the car while driving and at lower rpms it will be mellow but at higher rpms you put more stress on the u-joints and they will wobble/shift more. it sounds more like a diff problem to me. have you changed your gear oil in the diff yet? this may help. a clunking in the differential may signify either improper lubrication, or chewed gears (which will make the whining noise). when you change the diff gear oil look for large slivers of metal in the old oil. normally there will be a few but if you start pulling out large slivers and chunks then i would suggest either a new rear end ( perfect time to upgrade to lsd, either GSL to keep the 4x110mm bold pattern or do a SE suspension swap to get a more popular bolt pattern (4x114.3))

lego : change your diff fluids and see if that helps. part of the whining may be from improperly lubricated gears in the diff. thsi will cause them to get hot and wear prematurely. if this does not solve the problem i would look towards a diff rebuild or replacement.

trochoid

iTrader: (6)

Check your tranny and control arm mounts.

legokcen

iTrader: (8)

I was thinking it might be a bearing or a gear. Aside from fluid, what else can I check? Here's something I thought was strange... I jacked the car up and set on stands. When the engine was running and the transmission in neutral, I saw the drive shaft moving slowly. It didn't make scense to me. Is my clutch going too or do I have a bad gear in the transmission?

rotornoob

iTrader: (2)

hrmmm.....im nto exactly sure about the driveshaft moving when in neutral. do you know approx. how old the clutch is and how much abuse it has approx. taken?

Kentetsu

I've had the same thing for as long as I've owned my baby, but she's got over 200k miles on that rear end. There is quite a bit of slop in the diff as well. Planning on swapping out for a LSD rear this Spring. If yours isn't LSD then you might consider this a good time to upgrade...

Rogue_Wulff

Pretty normal, nothing to worry about. When the engine is running, clutch pedal released, and trans in neutral, the input and countershaft in the trans will spin. The output shaft will get a little drag from the 90W oil, and can start to slowly turn. This, in turn, causes the driveshaft to spin.