F250 Towing ????

We always tow in overdrive. From what I have been told in an Auto there is no problem using O/D as there is a viscous coupling or similar, but in a manual with actual gears the O/D gear is 1 to 1 and this puts too much strain on the gearbox when towing. I have spoken to the Ford dealers when it has been serviced and they seem to all agree that towing in O/D is OK with the auto. It sometimes kicks back on hills or when we are overtaking. If I am in a really hilly section where it is changing from O/D to D and back again, I take O/D off as it keeps the speed steadier in D. On the really big hill climbs it will go back to 2nd. Coming down hills such as Cunninghams Gap and the Toowoomba Range I manually put it back to 1st and the engine compression means very little breaking even with all that weight pushing from behind.

Brian just typed my reply. All of the above goes for us and the dealer said that OD towing is ok
Turist

Warning ! Techno babble following ........ Skip to last paragraph to avoid !! <smile>

The biggest killer of auto trans is heat causing the oil to oxidise and breakdown therefore not protecting the transmission from wear. The biggest cause of heat in a auto is the torque converter by nature of its slip or stall speed.
The heavier the load the more slip ... more heat ! The 4R100 Auto in the F250 takes care of this heat a few different ways like most modern auto trans.
The first thing it does is not generate it in the first place by using a lock-up torque converter.
Once the torque converter is locked the trans will actually cool down if is getting too hot.
Most of you will have noticed the 100 -150rpm drop under certain conditions it is not a gear change just the toque converter locking and unlocking. Locking the converter also saves fuel by bringing engine revs down to meet input shaft rpm reducing slip.
The F250 is also fitted with a transmission cooler that is operated by a bypass valve opened and closed by a temperature sensing resistor (thermistor). This allows the trans to warm up as quick as possible saving wear and if it gets too hot a valve opens and directs oil to the trans cooler to lower temperature.
I have fitted a permanent temperature gauge in the cabin to monitor the trans of my F250 and use this as a guide. If the trans gets too hot I can see it and take steps to cool it a bit.
The 1/8 NPT sensor screws into the pressure test port on the LHS of the trans ... unscrew plug screw in sensor ....Voila !!!
I have done a few tests both with the BT on and off .... and the first thing I noticed was the trans ( like the 7.3 engine) takes awhile to warm up. Without the BT on the trans takes depending on ambient temp about 20-30 minutes to warm up. So i wouldn't tax the trans for that period. The optimum temp for a trans varies according who you talk to but I believe that between 80-90c is fine. Towing the BT up the highway in summer 100k in O/D it sits about 85c. rising to 95c in Drive up a long range with periods of wide open throttle. I use about 110c (never seen it on F250) as an upper limit to start cooling trans either by locking converter or pulling over and placing trans in park and letting cooler do its job.
The oil in the trans on F250 I believe is a Synthetic (Mercon) Automatic Trans Fluid and can take higher temps than the old mineral oils.

Whew ! Finally to the point .... Letting the powertrain management control shift in and out of overdrive or doing it yourself doesnt overheat the trans therefore does not hurt it in any way in my opinion. I've tested both. Labouring the engine is the concern.
I mainly shift it myself using the max torque rev of 1800 as a guide below this I consider the engine to be labouring, especially, with BT on so shift it out of O/Drive. Although lately I,ve been using the 90- 95k rule i.e. with BT on I flick into O/D at 95 and if speed drops to 90k I flick out whether on flat, dirt, downhill or uphill ....
I also have a temp sensor in oil pump to monitor oil temp for turbo idle down but that's another debate .... I gotta get a life !!!!! <smile>
Regards
Anthony

Thanks guy's. Anthony Wow, chapter and verse but no doubt very accurate. I do like good information, I am curious though are you saying that you stop the rig if your temp hits 110c, but you have not got to that temp yet? Graham

Anthony I take it that what Turist and I are doing is OK? You really go into things in a big way.

Yes Graham .... if I saw 110c trans temp on the gauge I'd be concerned about reducing it.
The optimum range is 79c -107c and as a rough guide for every 11degrees the trans runs above 107c trans life is reduced by half if using Dexron II as your oil. With the new synthetic oils this data would need reappraising but is still a good guide I feel.
Because the trans oil runs through a cooler in the bottom of the radiator as well at temps of above 121c you can boil your radiator under sustained driving at this temp.

The HIGHEST I've ever seen on the F250 trans under a heavy load (BTon) Toowoomba Range is 95c ..... which proves how good the the system is in the F250. Hook up the BT drive away .....
The only thing I've found so far is that the trans should be fitted with an external trans filter
these filters look like inline fuel filters and have magnets to trap ferrous metal particles and a filter paper to catch other particulate matter. Mine is a Mar02 delivery and I dont know why it doesn't have it .... I'm searching for kit at the moment. These filters will greatly extend the service life of the trans.
According to Ford ....
Caution ..... Install a new inline trans fluid filter (XC3Z-7B155-BA) every 48'000k If the vehicle is not fitted with an inline fluid filter install an inline fluid filter kit Part No (XC3Z-7B155-AA)
I'll post a message when I find them .... price etc
Anthony

Brian,
What your're doing sounds fine to me ....but believe me I'm no self appointed expert I've just been tinkering with cars since I was a kid. I go into things with the F250 in a big way to keep it as reliable as possible. For years to come it has to take myself and family into the outback possibly by ourselves and that puts me straight outta my comfort zone. <smile>
If we can get some time off .....
Regards
Anthony