Trans Rattle

[bulitt]

New to me 2008 Viper. 13,000mi
No neutral rattle I can detect.
No noise from engine through rev range.
Getting a low rpm rattle near front of Trans. Driving along around 1500rpm. Step on accelerator and rattle starts. Hearing in all gears but most noticeable in 5&6.
Going down hill with slight throttle pressure- rattle disappears.
At idle I can hear TO bearing spinning. No squealing.
Trans shifts well in all gears, no grinding. No clutch slippage.
Nothing loose that I can find. Removed the underbody skid plate and cleaned all the rocks out.
Listened from underneath and sounds like noise coming from throw out bearing area. Slight rattle at idle.
In the past when I had one of these fail the screech was horrible.
I will say the rattle at 1500rpm also comes with a pretty severe vibration through the the shifter. When the car is not moving, trans in neutral, engine at 1500rpm there is no vibration which leads me to believe it is trans, shaft etc.
Checking sparkplugs today and fan.
Driving me nuts. Reminds me when I installed a 396 in my 71 Z28 without the externally balanced flywheel back in 1977. That was a quick fix.
Thoughts?

Fluid change tomorrow.
Thanks!

[viperBase1]

Considering the car is "new to you", I would start with changing fluids.

Clutch Fluid / Transmission Fluid / Diff Fluid.

I've adopted the "Fill twice" method.
Fill the fluid, drive it a little bit and then check the level again and top off...done.

Every time on 2nd check, I've found the "top off" was necessary.

[Redx]

There was a amendment in the owners manual stating that trans rattle at operating temperature is normal due the characteristics of the dual disc clutch. I'm away at the moment but I can grab a picture when I'm back.

Usually I get a pretty decent rattle in idle, but not usually in gear.

[bulitt]

Thanks Guys!

The fluid change cleared this up! New ATF. Hardly noticeable now!

[viperBase1]

Stuff is available on Amazon Prime for a good price:

Modifier LINK | Oil LINK

[Steve M]

I can think of a couple types of noises that are par for the course when dealing with these cars:

1. Clutch rattle - this should only really happen when the clutch is disengaged (i.e. clutch pedal on the floor), and would be from the plates rattling around. If it is the clutch making the sound, it should go away when you engage the clutch. I've never heard this sound from the stock clutch, so unless something is broken, it probably isn't the source of your noise.

2. Neutral gear rattle - this would be caused when you have the clutch engaged, but the shifter is in neutral. The gears in the transmission will be spinning, but under no load, so you'll hear the gears rattling as they load and unload from the engine spinning them. This became a problem in 2008 with the switch to ATF+4 transmission fluid, which is pretty much a 30 weight type of oil (comes out like water when hot). You can switch to a thicker oil (something closer to a 75w80), which will eliminate the rattle at the expense of increased shift effort when the fluid is cold. Donato recommends such an oil to help protect the internals better on a TR-6060 that is driven hard, and is why I made the switch in my own car. Again, with the car in gear going down the road, this probably isn't the source of your noise.

Do you have an aftermarket shifter by any chance? Poly trans mount? Anything that gets rid of the rubber isolation pieces as the car came from the factory will amplify noises that you wouldn't normally hear, so keep that in mind.