Tranny slipping off the line

[Audiofn]

I have a 1999 F350 that I have a tranny gremlin that has been driving me nuts. I even had the tranny rebuilt by Brians Truck stop and we are both stumped. To be clear Brian has been fantastic trying to figure this one out and I am very happy with his service.

The symtoms are as fallows. I can jump in the truck and drive it around for a while and all is good. If I pull over to say buy coffee or run into a store, after the truck is warm, when I drive it it will slip off the line. If I pull it down into 1 then it will take off no problem ussually, some times not but that is rare. We have dropped the pan and it is totally clean inside, replaced the solenoid pack and that did not change anything and replaced the black electrical shifter deal on the side of the tranny. Nothing has made any difference. It seems to happen worse when it is warm out so I really want to get this figured out as boating season is almost hear. Any thoughts on this would be fantastic as I am loosing my mind!

We also replaced the speed sensor recently.

[fixxxer22]

can you get ahold of a scan tool and monitor VREF on a datastream while the concern is happening? we are looking for a constant 5 volts on vref

[Audiofn]

What is VREF? I can probably get the scan tool my buddy has a snap on one and my brother has a cheaper one (I think it cost about 300 bucks or something like that) Is this something that stores and can be looked at later or do you have to look at it while driving? Is there a chance that something is getting screwed up like a connection to the computer?

Thanks

[scottw]

Go here, a lot of good info can be had.

http://www.ford-trucks.com/forums/index.php

[fixxxer22]

VREF is vehicle refrence voltage. we limit voltage to many processor inputs to 5 volts so spikes and differences in voltages when the headlamps and blower motor are on do not effect the accuracy of the sensors.

[Audiofn]

OK thanks. What do I do if it is out of spec?

[rchevelle71]

Are you using the correct fluid?? Not sure this is any comparison to a truck, but my '99 ford mustang uses a different fluid, cant remember the name of it, but its not just plain old ATF.

[fixxxer22]

Could you also please provide me your axle code on the sitcker inside the door?

[Audiofn]

Fixxer I will have to get that from my brother he has been driving the truck the last few weeks.

[Audiofn]

Are you using the correct fluid?? Not sure this is any comparison to a truck, but my '99 ford mustang uses a different fluid, cant remember the name of it, but its not just plain old ATF.

I hope so my buddy works for a Ford dealer and he got the stuff from them. The guy that rebuilt the tranny who is known as the best in doing these things said he really did not care what I used.

[Audiofn]

What is so odd is that it will work fine for a while then slip. You pull it down into D1 then it starts to work fine again. I was headed up to Maine last summer with a friends 311 and I came into the toll booth, tried to exit the toll and it did not want to move. Was able to coast over to the side of the road, could not get it to go even using D1. I let it sit for about 5 min, started it up and off i went no problems the rest of the trip.

[rchevelle71]

I hope so my buddy works for a Ford dealer and he got the stuff from them. The guy that rebuilt the tranny who is known as the best in doing these things said he really did not care what I used.

Just checking, if it had the wrong fluid, that might explain the heat thing, how it works fine until hot. I once had a buddy that had a jeep trans rebuilt at a respected shop around town, and blew it 3 times before they realized they were putting the wrong fluid in it.

[Audiofn]

I am going to get to take a look at this a little bit tomorrow. Is there an external filter on these things? I was researching this evening and saw a few guys talking about an external filter. Would this truck have one?

[Chris]

External filter on '04 and up

[Audiofn]

Ok slid under the car today and no filter. My buddy works for a dealer in the area and he grabbed his laptop and hopped in the truck with me today. We drove all over the place and figured it was not going to slip. Pulled over at a customers house for about 15-20 min and when we went to leave it slipped again. He said that everything including the voltage looked good. So he thinks that there is an internal hydrolic leak. What do you think?

[fixxxer22]

sounds like a cut piston seal or warped seal. something bleeding off pressure for a split second and then the internal pressure and volume overcomming the leak to act as normal as it can.