Today I went through a stretch of road that was very hilly with a speed limit of about 45mph. On the uphills my truck would downshift and rev up to about 2300-2500 just to maintain speed. It felt like it had a house behind it going up the hill but I wasn't towing anything. The tranny also stayed in gear going down hill when I was just trying to coast while overdrive was on. Is this normal or should I be concerned about something.
My thoughts.

Could larger tires (35") be causing this?
Could the last owner have put a tune in it that is causing this effect?
Could my tranny be going out? Every time it shifts it feels a little different to me.
Is this just normal and I am worrying for no reason?

 

The tires shouldn't have much of an affect on that. I had 36s and it almost never kicked down a gear to make it up a hill rpms never changed either. My boost would shoot up and it would feel like I was pulling a house
I'm intrigued to know more about the shifting "feeling different"

 

Depends upon the grade you were traveling. My truck does similar when in stock, but no problems when in a tune. My travels were in the black hills of South Dakota and the hill country of Texas. I am running stock size tires and a reman tranny. When the truck does the search for gears, I hit the button to drop out of overdrive.

 

I would venture to guess that with the larger tires, you are still running the stock gearing. Is this correct?

If it is, then the explanation is simple. At 45 mph your engine RPM's would be low enough at the pedal position required to move uphill that the PCM requests a downshift. It's not because the engine couldn't technically handle it in a higher gear, but rather it's because of the function programmed into the PCM at that specific speed, RPM, and pedal position triggers a downshift at that precise moment.

As for coasting in gear, yes that's normal too. It's not going to freewheel with the torque converter locked in 3rd and 4th gear.

Now if the EX has tunes or a chip on it, then the programming might have been altered, and the shift points massaged a bit. This would simply change the point when it would downshift, but the function is still present somewhere. Heck, the tuning can be altered so that the trans wouldn't downshift at all in that scenario. However, at very low RPM's and going uphill, it's not always best to be lugging the engine. You'll end up with the turbo not being able to spool up, and the result will be less airflow and more fueling all while EGT's begin to climb and the presence of smoke will be seen out the tailpipe.

Of course, I'm just basing this off the limited info posted. But I saw the same thing with my own truck years and years ago when I was running larger tires and stock 3.73's.

 

I'll add that reprogramming the PCM for the tire size should help this to some extent. Is your speedometer off?

With 3.73 gears and 33" tires you should see about 70mph at roughly 2000rpms.
With 4.10 gears and 33" tires you should see about 60mph at roughly 2000rpms.

The taller tires should give you a few more MPH at the same RPM's.

Good aftermarket tuning makes a BIG difference in how much the truck needs to downshift. I'm currently playing around learning about my new tunes and it takes a LOT more pedal to climb a grade and it downshifts much more readily in my 'stock' tune than it does in my 80HP tune. With cruise control on, it seldom downshifts and I see more boost pressure in 80HP - in stock, it downshifts at the thought of a grade and makes little boost until it downshifts.

In theory, I am getting better MPG with the 80HP tune since the engine is more 'efficient' making the same HP at lower RPM's. In reality, its much more pleasant to drive when the engine isn't all wound up and shifting all the time.

Keep in mind that not all aftermarket tuning is created equal. Choose wisely!

 

wow, thanks for all the info guys. Here is the info that was asked for. 3.73 gears, stock rebuilt tranny, when using gps actual is about 10% faster that speedo (55 speedo = 60.5 gps). Forgot to tell my wife this until she came home complaining about how slow everyone seems to drive when she is in the truck. The thing with the tranny feeling strange when shifting is probably me just being paranoid sense I haven't driven any other 7.3's. Ever sense I had a chevy tahoe tranny explode on me I am paranoid when a tranny shifts hard. The thing that gets me concerned is sometimes it feels like it bumps out of gear and then again going into gear and other times like it just bumps going into gear. I am guessing this in actually normal and is dependent on what the truck is doing? Also I have read about 100 pages now and am thinking about getting a DP tuner. How hard is it to get custom tunes done? or are the stock tunes ok?

 

Talk to Jody at DP Tuner and he can clear up a bunch of your questions regarding the tuner.

 

Its interesting you mention 45mph. I'm running canned tunes, and that is exactly the spot mine locks the TC in 60HP performance tune. I also have 35's and 3.73's. In my tow tune, it takes slightly more MPH and throttle input before it locks up.

 

If you can get your speedo calibrated for your tire size your truck will thank you!

 

Sounds about normal for mine, which is stock with 285/75'3, which is equivalent to about a 33". But if I pull the same hill at 50 instead (and there is a particular hill I have tested it on), it will not downshift. It's all about being in the power band. Try the same hill at a higher speed, and see if it doesn't downshift.

BTW, putting the 285's on mine made the speedo calibration PERFECT.

If you think the shifting is slushy, look into a John Wood valve body.