Unsure what transmission this is, 700R4? There is a throttle valve or kickdown cable present, and it is definitly an overdrive, behind a 4.3L.

If the vehicle is driven above 50mph, the tcase ends up coated with ATF on the driver side, near the front driveshaft yoke, while the transmission stays dry. The ATF level in the transmission does drop.

We do see a servo cover there, but it doesnt look like an obvious leak there. Because it only happens when driving at speed, everything blows back.

Any thoughts on this? Would this meet the symptom of a tranny output shaft seal leaking? Something about the vacuum lines on top of the tcase?? we've been researching this a bit, but are unsure on where to start..

Any suggestions would be appreciated.. The vehicle does run fine, all shifts are proper..

Thank you!

 

Trans is overheating and pushing fluid out of the overflow tube on the trans.