Noise from transmission

[NSX Swede]

I recently purchased my NSX -91 and discovered a soft grinding noise from the transmission when driving on a low gear (1-3) with a low rpm on the engine. I didn't notice this when I bought the car as the volume is low.
I have checked if the transmission is in the "faulty" range but it is prior to these numbers.
Anyone have a clue what it is? - is it serious?

Also, sometimes a metallic sound can be heard from the driveline, and it sounds as if there is some kind of backlash in the transmission - is this normal?

Any information on what to do and how to do it?

Regards.

 

[MiamieNeSeX]

Check the serail number on the transmission against the ones in snap ring. Sounds like you might have it. GL

Armando

 

[NSX Swede]

I have double-checked it and as I mentioned it is prior to the range of the snap ring problem.

 

[Briank]

Have you checked the oil in the transmision? How many miles does the car have on it.

 

[NSX Swede]

No I haven't yet but I will as soon as possible (doing some other issues as well as I just received the car).

The car has only 2K miles on the meter...

 

[pimp42]

When do you hear the backlash in the transmission?

 

[NSX Swede]

THe backlash "clang" is heard when driving slow on lower gear, and releasing/giving trottle.
Also if I raise the car and rotate the backwheels back and forth, I hear this noise and feels the backlash (about 5cm/2 inches on the periferi on the wheel)

 

[pimp42]

I have the EXACT same thing. First gear - give it a little gas, let off and you hear it thrashing back and forth?

Had mine looked at by an Acura mechanic, and he said replace tranny. Ouch. Do you know anyone with another NSX that you can listen to? I sat in another one, and heard the exact same thing - just not as loud. How many miles are on yours? Do you know how it was driven prior to you owning it?

m

 

[Larry Bastanza]

This is typical backlash gear noise. DO NOT REPLACE THE TRANNY

The other possiblility is your motor mounts are either loose or they need to be re-seated to minimize the noise. The front and rear mounts are what keep the drive train from rotating fore and aft as you apply throttle, sometimes they are loose and will make a clucking sound on/off throttle. Check them. The procedure I use is to loosen the front and rear mount bolts, start the car and throttle the engine a few time as you watch if rock, turn off the engine and retorque both mounting bolts.

Also check you right and left upper trans and engine mounts too for proper torque. I think they are all 69 ft.lbs., please check the service manual to be sure.

My 1991 has 35K miles and has the exact same gear noise. NO worries.

HTH,
LarryB

 

[pimp42]

That's kind of the way I was gonna deal with mine. I've tried to adjust the mounts, but with no luck. I've adjusted them as discussed here on Prime, as well as cranking them down with the engine rocked to the back (or front, can't remember.) Throw the thing up on jack stands, lie underneath the car and slowly rock the wheels back and forth, and you hear it plain as day. The only problem is that it just sounds so much worse when you're driving...