Transmission rear seal leak

[Creatve]

I have a 99 2wd auto 4.0L SOHC sport and after helping out my buddies who was stuck out in the mountains(7 of us in my 2dr explorer going up a mountain offroading), I saw small patch of ATF fluid on my garage floor. I looked up and it appears to be leaking at the rear of the transmission where the driveshaft connects.

Is it normal for this to leak while offroading?(especially being fully loaded with people going up a mountain) If not, whats involved in replacing this seal (tools used, procedure) and is it wise to also flush the transmission fluid and replace the filter? I tried looking in my Haynes manual for replacement of that seal but I cant find it in there.

My transmission code is D so I guess its the 5R55E tranny(18 bolts). Got about 113,500 miles and never changed the tranny filter but had a tranny flush at 77,000. Any help is much appreciated. Thanks

 

[BrooklynBay]

It's possible that some fluid might have leaked out of the overfill vent during off roading.

 

[Creatve]

oh theres an overfill vent in that seal or around that area?

 

[BrooklynBay]

The vent is on the upper rear of the case.

 

[Creatve]

Thanks, I'll clean everything down with brake cleaner and see if it still leaks. So far there is no new atf leaking