I have a 96 F-350 with the E4OD automatic trans. It will shift on thru the gears and into OD by 45 or 50 mph if you are just driving normal. Then if driving around say at 55 mph if you let off the throttle it will fall back to just above idle rpm and it feels like the trans goes into neutral. If I take OD off and then let off it feels like it is still in gear and the rpm stays up like it should.
I have also noticed that when pulling heavy load when you let off the throttle that the trans temp will jump up.
Does anyone have any ideas?
thanks RB

 

My 97 would pause and hold the rpm range for about 30 seconds and then would drop like what seemed to be neutral too....

I will note that mine is now in the shop for a trans rebuild.

 

Sounds like your TC is unlocking, usually it unlocks when you tap on the brakes. As far as the trans temp, sounds like you need to get rid of the stock trans cooler and get a bigger one.

 

My 97 would do just as Lee describes. How many RPM's are you turning at 55mph? Also, as to the temperature jumping when you let off, do you know how many degrees it jumps?

 

Forgot, with the TC unlocking, the temps go up.

 

That makes sense...more friction more heat....

 

I forgot to mention that I do have 2 aftermarket trans coolers 1 small and 1 larger one.
What is a TC?
I am running about 1500 rpm at 55 mph.

 

TC is the torque converter.

 

TC=Torque Converter, Torque Converter Clutch. 1500rpm's at 55mph may not be fast enough to keep the torque converter clutch engaged. I know my 97 acted just as Lee describes. The TCC would stay locked in going down a hill at 60 or so mph, but after 30 seconds, it would unlock. My truck had 4:88 gears in it though, and would run at 2600rpms at 70.

 

What can I do to fix this replace the TC? My truck has 3.55 gears. When pulling heavy loads my truck will run in the yellow on a B&M gauge and when I let off and it coasts it will jump up in the red, but when I get back on it it will start cooling off.
thanks RB

 

You have to pull the trans to replace the TC. It also might be an electrical problem somewhere, like in the brake light wiring.

 

How could this problem be connected to the brake light wiring?

 

Its setup that way on our trucks, touch the brakes and the TC unlocks. Programing sometimes will help to stop this.

 

Does your truck drop to idle speed instantly once you let off the pedal? Or does it take it a while like 20 to 30 seconds? How does it operate at 65 or 70 mph?

 

at 55 mph it drops back to just above idle instantly, when I am running at 70 75 it drops instantly also but only drops back to about 1000 rpm. I am not touching the brake just letting off the throttle. And as soon as I let off you can see the trans temp go up.