What?
Explain gear roll over noise
- Thread starter BrianX128
- Start date
What?
MTKirk
Full Access Member
'tis true. Our hydraulic clutch system (all hydraulic clutch systems as far as I know) operate with the TO bearing constantly pressurized against the pressure plate fingers (thus the bearing flange and interior spins any time the flywheel is spinning). This pressure is applied by a spring in the slave cylinder that applies pressure at just under the deflection rate of the pressure plate fingers. The slave applies this pressure even if the mechanical linkage or hydraulic system is disconnected or fails. In this way the system self adjusts to the wearing clutch disc, this is why modern clutch pedals never need adjustment.
True, but with not much pressure as you mentioned.
FWIW I recall "agnem" recommending that people with a SMF use non-detergent 30wt motor oil in their trans to help quiet the rollover noise.
MTKirk
Full Access Member
I change to 40W Rotella in the winter, summer I use sta-lube gl-4 85W-90. The Rotella is quite a bit thinner and the transmission definitely rattles more with this oil when it gets warm (and thinner). So I think the thicker the lube the less rollover noise. Gear whine is exactly the opposite, the trans absolutely howls with 85W-90 on sub zero mornings (why I change to 40W lube).
T-19 yes, use gear oil of your favorite weight.
ZF5 - no gear oil. ATF or straight 30wt.
Heath
I tried that, and hated it. I could not shift the tranny in the winter. I called him on it and he admitted he had a long driveway and by the time he got to the end he could shift it? I then tried 10w30. It was better, but still have some stiff shifting when it was really cold. Listening to the roll-over noise, I realized the higher the idle rpm, the quieter the tranny was. I had already bumped the idle up a little bit, and I only had a lot of noise when the tranny was cold, while it was dragging down the rpms of the engine. I had a hunch, put the correct dexron atf back in it and sure enough, it has less roll-over noise with the atf because the thinner oil lets the tranny turn easier, letting the engine idle faster, eliminating the noise. And it shifts so much better with the correct oil.
