27th of November 2017 ... Number of Responses 2 --

what would cause oil to be standing on top of transmission?

Could be several reasons for this and it is not clear from the question whether this is Engine Oil or Transmission Fluid or what make / model / year of vehicle it is. Here are some possible reasons: 1 - Transmission is overfull and thus venting fluid. 2 - Transmission has been under load recently and thus heated up to the point it vents fluid. 3 - Oil Leak higher up in Engine which flows down to the top of the transmission - Oil Lines and hoses leaking, Turbo Seals failure, Valve Cover Gasket leak, Rubber Seals around bolts dried up and no longer working etc. Finding oil on top of the transmission is not unusual for an older vehicle due to gasket, hose and seal wear.

Leak in the pan – The transmission pan is not invincible and is subject to wear and tear. Leaks can be caused by a puncture in the pan itself or loose bolts/drain plugs that are not properly tightened. When you’re driving on the road, your transmission is susceptible to loose rocks and other inconveniences that can strike and damage the pan. If a big object punctures the pan, it will cause a rapid amount of transmission fluid loss and you will be able to tell right away. If it’s a small puncture it might take a while before you notice any signs of leaking. Loose bolts or drain plugs can also cause a transmission fluid leak, which is why they need to be tightened properly after a fluid change or flush. Fluid Lines – The transmission’s fluid can also be damaged by heat or debris. Debris on the road can puncture fluid lines at high velocity. While that’s not always the case, heat can cause cracks in the line as well. Pan gasket – The gasket that lines the pan can also cause a transmission fluid leak. Old gaskets that are frayed and cracked can allow fluid to escape, and so can gaskets that aren’t properly aligned (which causes it to warp), which prevents it from sealing properly. If you need to replace the pan gasket you can find them for under 20 bucks and it’s just a matter of removing the pan and switching out the gaskets.