strange noises from the auto tranny

[wayneoR3M]

well im always one for listening for odd noises here n there and the other day started her up as normal .pulled out the drive . all good. accelerated and noticed a whine from the gearbox at around 2500rpm . only for a second or two till it changed to 2nd and then the same around the same revs .....??? i know shes due an trans oil change ... ...... any ideas. ima bit worried

[k9sar]

never a good sign when your auto tranny is making noises like that. I would immediately check your fluid levels and do a tranny fluid change. Look at what comes out and hopefully it's not cloudy. I'm not an expert on auto trannys but I would suspect something like a bearing going bad or perhaps starting to burn a clutch disk surface.

[Slartibartfast]

You sure it's the gearbox? My timing belt tensioner made a whining noise at a certain RPM and had my mom thinking the trans was going out. But so long as it's due, change the oil!

Edited February 22, 2013 by Slartibartfast

[wayneoR3M]

changed the oil tnight a bit brownish filled it with the atf we got at work and now ive got no drive . ... sounds like its cavitating .... so im gona let it sit till monday n check the level again noise is definately coming from the bellhousing . . cars still at my work .... im pissed about this ..... any ideas guys ??

[Alkorahil]

Was it NissanMaticD or Dex/MercIII fluid that was used?

Did you at any point have an A/T temperature light on the dashboard come on?

Any other type fluid should not be used.

Was the transmission filled up to proper level? Make sure to check fluid level while vehicle is in N not P.

 

I assume both were done but have to cover all the basics first.

 

However, based on what you are describing, I think you have a torque converter valve or pump issue you are dealing with.

Torque converters are sealed units that pump hydraulic fluid in and out of the converter to move the plates together or apart. This hydraulic fluid travels through a torque converter clutch lockup valve. Either this valve or the pump that supplies it can go bad, resulting in low or inconsistent fluid pressure. As with the other possible mechanical problems, this problem allows the disks to alternately grab and lose grip.

You could also have a worn Friction Plate, but doesnt seem to fit your symptoms posted. Torque converters, like manual clutches, use friction to accomplish their job. A metal disc or plate covered with high-friction material presses against another plate to transfer the power from the motor's crankshaft to the transmission. The converter increases the pressure as the transmission handles the speed without choking the engine; it also decreases the pressure so the plates can separate when the transmission cannot turn quickly enough. If the friction plate becomes worn, it rapidly grabs and slips at high speed.

 

 

There are also damper springs in the converter that can also go bad. The torque converter clutch engages and disengages rapidly, both in response to changes in gas pedal pressure and movement in the suspension system. The damper springs act like small shock absorbers, preventing the disks from bouncing wildly when they join or separate.

 

These issues are usually caused by heat. Heat is bad for an automatic transmission. A secondary issue is simply age of the unit and how many miles are on it.

As transmission fluid recycles back through the turbine, it picks up frictional heat. Once the amount of heat generated by this friction surpasses the transmissions cooler's ability to shed it, the fluid thins and power transfer becomes inconsistent. Other sources of heat build-up are are failing transmission clutches or bands, and blocked coolant lines or radiator. Overloading the transmission also produces excess heat, as anyone who has towed a heavy trailer up-hill can attest. Once the transmission fluid has been overheated enough times, it becomes permanently de-polymerized and need to be replaced.

The stock cooler on these vehicles is prone to clogging as the vehicle gets older, causing the transmission fluid to not cool as effeciently as it should or not circulate at all causing transmission damage. In addition the stock cooler is 'just big enough' for normal operating temperatures when new, a heavy load or high external summer temperature areas will cause the fluid not to cool as effeciently as well as it can not dissapate heat fast enough.

There are several threads on here about bypassing the stock transmission cooler and using a larger cooler in its place.

[mluczaj22]

strange ive never heard a autotrans make a whinning noise. my pwr steering pump does though when cold. but my trans is slow to go into drive and sometimes the converter wants to unlock and lock at cruise sometimes. but other then that it shifts fine when taking off. im guessing the converter is bad? lol. strange...

[ThaBigPerm]

Well, I have a torque converter that (eventually) needs replacing. Symptoms to narrow it down to TC (as opposed to pump or AT internals):

 

Whining noise when engine is loading transmission (either going down the road with foot on gas, or stopped in a forward or reverse gear).

Whining goes away in P or N. Revving the engine in P or N does not produce the whine.

Whining goes away when TC goes into lockup, even with loading (whine comes right back when TC jumps out of lockup).

Whine also is not linear with engine speed or trans input speed - the whine actually follows the difference between engine speed and trans input speed - whine pitch increases up to stall speed (~2100rpm diff) and hangs out there no matter engine RPM if accelerating/loading.

 

My whine also has a "cavitating" sound quality to it, but my understanding is that the bearings (stator?) are shot ... or nearly so.