Originally Posted by Y2KW57

1. NO. It is not at all necessary, nor even desired, to keep the transmission temps under 160F constantly. Have a look at my transmission gauge as an example:



Have a look at the range of temps and the color coding of the gauge. 160F is in the yellow, just like 245F is in the yellow. There is such a thing as transmission fluid being not warm enough. 175F is considered by many experienced operators to be optimal, and our resident retired Ford automatic transmission engineer who spent much of his career monitoring transmission fluid temperatures for automatics during development, has repeatedly reiterated that anything under 220F is safe. In fact, the 4R100 can endure temps up to 250F for brief periods of time (about 30 minutes). I raise eyebrows when the temp reaches 200F, but 160F I would consider not warm enough yet.

2. YES. And that advice was listed as #1 for a reason. I bought a couple of F550's with the 7.3L... the first one I got for me, and the next one I ordered for a small company I consult. The company president didn't want to spring for 4x4, despite my strongly advocated advice that it would save the company money in the long run, due to the gear reduction utility of the transfer case. The company 550 is now on it's 4th transmission. My 550 is still on it's original transmission, with no work done to it other than fluid changes. Every catastrophic transmission failure to the company 550 happened when backing up loaded, but not overloaded, as the trailer is only an air compressor, which is less weight than the chipper you probably pull.

You'll know when to throw it in 4 LO. You'll feel it as the torque converter winds up without you going anywhere... not from a lack of traction... but rather from the presence of traction which cannot be overcome by the 4R100's too tall of gearing. That's where the 2.71:1 reduction remedies the problem.

3. To OD or not to OD is a driver input that manages more than just the transmission. That decision is also a way to manage exhaust gas temperatures when climbing steep hills while loaded, and is furthermore a way to mitigate brake overload on the descent, as it is said that a hill should be descended one gear lower than the gear needed to climb the hill. Again, you will feel when OD is getting in your way climbing, but you will not see your exhaust gas temperatures without another gauge (pyrometer), which I highly recommend. Since the 4.88 ratio is a different animal than the 3.73 or 4.10 gearing in your F-350s, you may find less of a need to shift out of OD afterall.

I shouldn't say "need", I should rather say desire. The transmission is automatic, and will automatically drop out of OD when the computer finally compares the inputs it receives with the look up tables and commands programmed into it's calibration. But the obvious issue is, the PCM does not have a forward looking camera with an image processor that can interpret the road ahead, or the intent of the driver. Hence the "need" sometimes to help the computer out a little, since we know where we are going and have a windshield view.

4. Correct. Performance tunes do not prolong transmission life. Some performance tunes, even so called towing tunes, are strongly suspected to reduce transmission life.

5. The major missing element of your summary is whether or not you have an Oil To Water transmission cooler in your radiator, and whether or not you have an Oil to Air transmission cooler that is larger than what originally came with the 1999 F-550. The presence of these coolers is CRITICAL to your transmission life, and should be included in any summary of actions you take to preserve your transmission.

Originally Posted by eyyu

Y2KW57,
I took the rubber cover of the heat exchanger pack and try to find out exactly what I have, here is what I found out.
I do have the oil to water radiator. ATF line from the tranny, goes into the OTW cooler then comes out into the factory quarter sized ATF cooler. It then enters into a smallish ~2" inline filter before goes back to the tranny. So, I think that this is really good news for me. I'll just have to see how well the system works in the heat of the summer, working hard. Thanks again for all the helpful insights.

Originally Posted by jstihl

I have a F-450 and and also run a tree service, I commonly haul a large dump trailer full of logs & noticed that it is always difficult to backup when I am not on pavement. I tried putting it in 4 Low when backing up on a soft dirt road today and I could not believe the difference! I wish I would have known about this a long time ago. I didn't realize that you can put in 4 Low without locking the hubs, is this the same for going forward? When do you absolutely have to lock the hubs?

Originally Posted by Y2KW57

The factory stall speed in our stock torque converters has been well argued to have been set too high for our diesel engines, so that is one reason why I'm very curious what RPMs you are running on these switch backs when you have manually locked up? I'm curious if you dropped from D to 2, or dropped from 2 to 1, would your calibration lock up your converter automatically at the increase of RPM, regardless of your road speed being below 32, based on the calibration sensing engine load? I'm also curious about not only the loss of torque multiplication with the manual on demand lockup switch, but also the loss of the fluid "fuse" between the connecting rods and gravity's power pulling the trailer down the hill while the truck is trying to pull it up the hill.

Originally Posted by Y2KW57

When do you absolutely have to lock the hubs? When you have lost traction, or anticipate losing traction, on the rear axle... and want the front axle to assist in transmitting power to the ground due to the slippage of the rear axle. Or when you want to "exercise" the lubricant in the front axle. Other than that, I cannot think of another situation when you "absolutely have to lock the front hubs" for those of us with manual locking front axles, which is all that F-450/550's were equipped with during the 1999-2003 era.

Because my F-550 has a TruTrac helical gear traction assisting differential (the OEM Limited Slip), I have never needed the front drive axle to transmit power to the ground, so I only lock the front axle to exercise the lubricant occasionally. I probably should do that this week, as it has been a while. I only do that on soft/slippery surfaces by the way, to prevent driveline bind.

By contrast, I manually shift the 4x4 lever on the floor into 4 LO routinely, in both forward and reverse, when I can see or feel that the auto transmission will be stressed. I use it on pavement and soft ground alike, but find that more typically, I encounter resistance off pavement far more frequently than on pavement. I park the truck off road, in what in winter turns into more or less a mud field, so there are times when 4LO (in 2wd) simply helps the transmission move the truck to the pavement with less strain. I then shift the trans to neutral, throw the lever back into 2 Hi, and roll on my merry way.