Transmission overfill

[Yuk]

Why shouldn't one overfill a manual transmission?

If filled while on ramps, on an inclined driveway, I can add an extra 1/2 quart to my transmission. How bad is this?

 

[Doug Hillary]

Hi,
depending of course on the box and its design overfilling could cause foaming and may lead to seal damage and etc. This may be caused by a "hydralic" effect and thru lack of breathing or gear immersion. It is all relevant to the overfill volumn of course

Undefilling is just as bad - especially when climbing gradients under load etc

Many different end results can occur from either

Truck transmission makers have done much research on this issue

Regards