I've got a 727 behind my big block that will not stop leaking. Every time after I run or drive the car then park it it leaks from somewhere. I have replaced all of the pan bolts with studs and a new gasket. I have swapped speedo housings and O-rings several times. I have also changed the tailshaft seal. Am I missing something? I'm really racking my brain here and just thinking of letting the car sit and only drive my Roadrunner this year. It is beyond aggravating to have to put fluid in this car only to have it leak out.

Common place is the shift shaft seal

Also replaciong the gaskey wont help if the pan rail holes are coined over. Easy to have happen in a stock type pan. Easy to hammer flat to.

Replacing the ouput shaft seal will only last a short time if the bushing is toast.

the pan rail is fine when I put the studs in I looked that all over to make sure. Also the seal and bushing in the tailshaft are new and have been checked to make sure they were put in right and not worn. How hard is the shift shaft seal to replace? Thanks for the quick answers.

CLEAN the trans off well ... let it dry ...and the sprinkle-on some baby powder.

THAT will show where the leak is coming from.

well I took off the trans cross member and where all the fluid is concentrated it seems like the small plate that hides the C clip the holds on the extension housing. I'm going to start there and clean the area and put either a new gasket/silicon or just silicon. Thanks

Check this, took me awhile to find.

https://board.moparts.org/ubbthreads/show...&PHPSESSID=

I posted on that thread about the use of JB Weld. It did work fine--finally sold car. Wouldn't hesitate to do it again under the same circumstances.

My sons car was leaking from that oring,i jacked the back of the car up so all fluid went forward.I then cleaned and blow dried the area and covered it with red silicone,it was a rig but beat pulling the trans.

jack up the back,clean with brake clean,air dry,cover with mopar black ATF/RTV and let cure over night

shaft seal is not hard and there are 2 of them,one for the throttle pressure valve lever under the e-clip and washer and the selector seal in the case

IMO it best to drop the valve body and use a jack screw to pull the seal into the case

and with the VB on the bench you can keep every thing from moveing when E-clip is removed,then use a pick to remove the rubber seal for the TPV,you can also clean up the part of the shaft that will be sliding thru the seal so it wont cut/roll the lip and leak

at this time when the pan is down ,I also replace the o-ring on the dip tube and use some of the mopar ATF?RTV on it as well

let cure over night and refill in the am