2000 f350 4x4 pds 74k, automatic, with super chip programer set on performance tow (6000 lbs. or less). Did about a ten mile climb in 45 degree temp. pulling a trailer that weighs approx 5000. had overdrive up and held it about 40 mph and 2000 rps as an average. all was fine as has been many other times driving to this point. backed into a driveway and let idle for 5-10 min. got in and put in first gear and started to descend at about 15-2000 rpms. about 5 miles down my first thought was the trans shifted into second gear which was odd. i come to find out after hitting the gas that no one was home, tried second then drive with same result. shifted to neutral and pulled off road to the smell of trans fluid. looking under the truck i look first at cooler lines but all is dry. looks like leak occurred somewhere in the tail end section of the trans on the left hand side. had dad start it breifly to see if i could locate leak but didn't have any luck. may try adding fluid to unit and restarting to view. I pull lawn equipment in the summer and plow in the winter with this truck. Did first trans service with synthectic and filter at 17k, changed fluid only at approx 40k, and did fluid and filter again at approx. 68k. each time shop said no fillings were found in pan. any one have any ideas before i tow it to a shop.

 

No idea, but someone will be along shortly.

 

The switch that tells the PCM what gear you have selected is located near where you report the leak. It is connected to a shaft that runs into the case to the valve body. If something happened to the shifter and that switch, your PCM may not be getting the information it needs to control the transmission.

This could just be a symptom of a bigger problem inside the tranny.

 

There have been posts here about never using 1st gear (on a 4R100) to retard speed. Said to be the weakest gear of them all.

Could be related(?).

 

Thanks for info. Only had one quart of trans fluid at the house. put it in and started to see if I could find leak but no luck. off to the trans. shop tomorrow. thanks for the help. send up a prayer.

 

That's one of the things the TransGo fixes -- keeps up the holding pressure on the clutches to keep them from slipping all to hell when you're in manual low gears.